Corrosion and Materials Degradation doi: 10.3390/cmd7020026

Authors: Huda Alqahtani Amal El Tohamy Ahmed Aboelmagd Salah Rashwan Abdel Aziz Fouda Medhat Kamel

In the original publication [...]

Corrosion and Materials Degradation doi: 10.3390/cmd7020025

Authors: Lourdes Merino-Galván María V. Biezma-Moraleda

This study analyses the behaviour of brass CB773S with extra-low-lead content in relation to corrosion and the corrosion–cavitation phenomenon. Electrochemical corrosion tests, both potentiodynamic and potentiostatic, as well as corrosion–cavitation tests, were conducted. Various potentials were applied to brass, alongside cavitation generated by an ultrasonic bath. Artificial seawater and artificial brackish water were used as electrolytes. Surface damage was evaluated using a stereo microscope and scanning electron microscopy. The results indicate that the interfaces between alpha and beta phases of brass serve as preferential sites for the nucleation and collapse of vapour bubbles under cavitation conditions, leading to a deep pitting, especially in artificial brackish water under this synergy. Susceptibility to a selective corrosion of the Zn-rich phase was observed, highly dependent on the test solution, as well as on the applied potential during the tests. The corrosion–cavitation synergistic damage was strongly dependent on the electrochemical parameters, particularly the applied potential, which plays a key role under cathodic protection conditions. In general, it can be concluded that low-lead brass behaviour is governed by a complex interaction between applied potential, electrolyte chemistry, microstructure, and mechanical effect. These findings provide valuable insights into brass’s performance under service conditions where corrosion and cavitation may appear simultaneously in marine environments.

Corrosion and Materials Degradation doi: 10.3390/cmd7020024

Authors: Agathi Dimakopoulou Markus Brand Jan Bohlen Petra Maier

For the corrosion behavior of three extruded Mg alloys (WE43, Mg10Gd, ZX10), the corrosion morphology and the resulting local stress distribution are correlated with the residual strength using µCT, Digital Image Correlation and tensile tests. Samples are corroded in HBSS at 37 °C for various exposure times to increase the extent of corrosion. They are then examined by using the gravimetric method to determine the corrosion rate. Corroded tensile samples are subjected to µCT analysis before and after tensile testing. The crack formation originating from pitting corrosion is discussed on the basis of the stress distribution around local corrosion—its extent is clearly influenced on the morphology. µCT analyses reveals that fractures occur in different ways, either at the smallest cross section, at isolated deep pitting sites, or in other critical areas with critical pitting quantity or size. Mg10Gd has a slightly higher strength compared to WE43 and ZX10. ZX10 maintains superior residual strength over time. Pitting corrosion is mainly observed in Mg10Gd and WE43, with different degrees of residual strength. This study allows for a better understanding and prediction of critical areas of non-uniform corroded Mg alloys and provides information on the bearable stress concentration.

Corrosion and Materials Degradation doi: 10.3390/cmd7020023

Authors: Tetsuya Suzuki Norihiro Otaka Kazuma Shibano Yuji Fujimoto Taiki Hagiwara

This study proposes a new deep learning-based approach for detecting pitting corrosion on stainless-steel sheet pile surfaces in drainage channels. Conventional ultrasonic thickness measurement methods cannot detect microscopic pitting corrosion that occurs before measurable thickness reduction. The research develops an automated detection system using visible images captured with smartphone cameras and U-net semantic segmentation. Two stainless steel grades (SUS410 and SUS430) were exposed for 5 years to a brackish water environment and analyzed. The deep learning approach achieved F1-scores of 0.831 (SUS410) and 0.808 (SUS430), outperforming binary thresholding methods (F1-scores: 0.407 and 0.329, respectively). Data augmentation improved performance by 1–3 percentage points. The method enabled non-destructive, quantitative assessment of early-stage corrosion using readily available equipment, providing a practical tool for infrastructure maintenance and long-term durability evaluation.

Corrosion and Materials Degradation doi: 10.3390/cmd7020022

Authors: Yusreni Warmi Nofriady Handra Agus Sukarto Wismogroho Syukri Syukri Sitti Amalia Andi M. Nur Putra Hamdi Habdillah Martini Martini Muhammad Naufalun Nabil

Flashover events can induce rapid surface condition changes on outdoor ceramic insulators, while early-stage degradation is typically assessed indirectly through long-term ageing or electrical diagnostics. This study proposes an event-based, surface-focused evaluation framework to assess short-term flashover-induced surface degradation using normalized wettability indicators. A controlled experimental comparison was conducted on uncoated, TiO2-RTV-coated, and SiO2-RTV-coated 150 kV ceramic insulators subjected to a single flashover pre-stress under humid tropical conditions. Static contact angles decreased from 42.6° to 18.3° for uncoated ceramic, from 112.4° to 86.7° for TiO2-RTV, and from 115.8° to 92.6° for SiO2-RTV after flashover exposure. The corresponding relative wettability retention values were 43.0%, 77.1%, and 80.0%, while the wettability degradation index values were 0.57, 0.23, and 0.20, respectively. Surface morphology and elemental presence were qualitatively examined via SEM–EDS. The results show that both nanocomposite coatings effectively preserve post-flashover surface hydrophobicity compared with uncoated ceramics, with the SiO2-RTV system exhibiting the highest short-term wettability retention. By integrating static contact-angle measurements, qualitative surface morphology, and normalized wettability indicators, this study proposes an event-based evaluation framework for RTV-coated ceramic insulators. Flashover-voltage and leakage-current measurements were included only as supplementary validation to support the surface-based interpretation, without implying direct electrical performance modeling. This surface-focused, event-based approach provides an experimental basis for post-flashover condition assessment of ceramic insulators operating in humid outdoor environments.

Corrosion and Materials Degradation doi: 10.3390/cmd7010021

Authors: Rafael Antonio Rodríguez Ospino Cristhian Manuel Durán Acevedo Jeniffer Katerine Carrillo Gómez

Corrosion in steel pipelines can cause critical failures in industrial systems, while conventional inspection methods such as radiography and ultrasonic testing are costly and require specialized personnel. This study presents a mobile computer vision system for automated corrosion detection inside steel pipes using deep learning-based visual analysis. The proposed system consists of a Raspberry Pi 4-based mobile robot equipped with a high-resolution camera for internal inspection. Acquired images were processed using color-space transformations (RGB–HSV), filtering, and segmentation. Convolutional neural networks and semantic segmentation models, including YOLOv8-seg (Instance segmentation) and DeepLabV3 (Semantic segmentation), were trained on a custom corrosion image dataset to identify corroded regions. Real-time visualization was implemented via Flask-based video streaming. Experimental results demonstrated high detection accuracy for uniform corrosion, achieving a mean Intersection over Union (mIoU) above 0.98 and a precision of 0.99 with the YOLOv8-seg model. These results indicate that the proposed system enables reliable and automated corrosion inspection, with the potential to reduce inspection costs and improve operational efficiency. Future work will focus on enhancing real-time performance through hardware optimization.

Corrosion and Materials Degradation doi: 10.3390/cmd7010020

Authors: Andreas G. Varias

Hydrogen-induced crack growth initiation, in metallic structures, is studied under constant temperature and chemical equilibrium, by employing Chemical Equilibrium Fracture Mechanics (CEFM). The conditions of small-scale, contained and large-scale hydrogen embrittlement are introduced and the areas of material deterioration, together with the distributions of stress and hydrogen concentration, including hydride volume fraction, are derived analytically. It is shown that the shape of the material deterioration zone is identical for embrittlement caused either by hydrogen in solid solution or by hydride precipitation; the size depends on the strength of the asymptotic crack-tip field, which develops by the mechanical loading in the hydrogen-free structure, as well as on the average hydrogen content absorbed by the structure. It is also shown that a linear relation exists between a power of the threshold of crack-growth initiation and the logarithm of hydrogen content, depending on the extent of hydrogen embrittlement and material elastic-plastic deformation. These linearity trends, which are derived by the present analysis, are confirmed by published experimental fracture mechanics measurements on several non-hydride- and hydride-forming alloys, including α/β hydride-forming alloys. The present study promotes structural integrity assessments, without reliance on complicated coupled numerical analysis of material deformation, hydrogen diffusion and hydride precipitation.

Corrosion and Materials Degradation doi: 10.3390/cmd7010019

Authors: Rujian Chen Chuanxiao Peng Xianrui Wang Mingxu Wang Jiali Cui Yuanjun Zhou Li Wang

Zn-Fe-Cr coatings were successfully deposited on sintered Nd-Fe-B matrix through the addition of the complexing agent etidronic acid (HEDP) to the plating solution; the electrodeposited process of the metal elements and the corrosion behavior of the coatings were also investigated. Through cyclic voltammetry (CV) tests, it was observed that the reduction potential difference between the metal elements was reduced by the addition of HEDP, which contributed to a more feasible electrodeposited process. The surface of Zn-Fe-Cr coating was covered by a chromate conversion film, and its microstructure was identified as the solid solution of Fe and Cr in Zn matrix. Compared with Zn and Zn-Fe coatings, the corrosion current density (Jcorr) of Zn-Fe-Cr coating was decreased to 0.28 × 10−6 A·cm−2, and the corrosion potential (Ecorr) was increased to −1.01 V. Compared with the Zn and Zn-Fe coatings, the corrosion rate of the Zn-Fe-Cr coating has decreased by 90% and 98%, respectively. The corrosion resistance of coatings was further analyzed by neutral salt spray tests (NSS), and the analysis results showed that a composite oxide layer, composed of ZnO and Cr2O3, was formed in the corroded area of Zn-Fe-Cr coating during the corrosion process, which is capable of effectively inhibiting the expansion of the corrosion area. This research provides a promising strategy for ensuring the long-term service integrity of sintered Nd-Fe-B materials in marine environments.

Corrosion and Materials Degradation doi: 10.3390/cmd7010018

Authors: Pengcheng Wang Kun Li Haiqing Guo Jianwei Di Yongde Zhang Faling Yin Yonghai Gao

When a H2S-containing gas kick occurs during drilling, the formation fluid containing hydrogen sulfide is mixed into the drilling fluid. Drilling fluid containing hydrogen sulfide is prone to causing hydrogen embrittlement when it comes into contact with the drill string during the upward return process. However, research on the risk and timing of hydrogen embrittlement in drill pipes remains limited. This study constructed a risk area and hydrogen embrittlement time analysis model. The risk area and time of hydrogen embrittlement in the drill pipe of the Jinyue 402 well in Tarim Oilfield were analyzed using the constructed model. The results indicate that the concentration of hydrogen sulfide in the Jinyue 402 well is in the area where the corrosion rate of steel increases rapidly, and the partial pressure of hydrogen sulfide is higher than the critical partial pressure at which corrosion cracking occurs. Taking into account the pH of the drilling fluid, fluid flow rate, hydrogen sulfide partial pressure, drill pipe tensile stress, hydrogen sulfide concentration, and gas partial pressure, the high-risk area for hydrogen sulfide corrosion damage in the Jinyue 402 well is 0–1680 m. The predicted highest risk point location and hydrogen embrittlement time are at a well length of 280 m and 21 h. Further predictions were made for the hydrogen embrittlement length and time of the Tazhong 83 and Zhonggu 503 wells in the Tarim Oilfield. The maximum prediction errors for the hydrogen embrittlement position and time of the drill pipe in the three wells were 4.8% and 5.2%, respectively. This indicates that the model can be applied to wells with different geological conditions and hydrogen sulfide concentrations.

Corrosion and Materials Degradation doi: 10.3390/cmd7010017

Authors: Clarissa Glawe Michael Raupach

In the original publication [...]

Corrosion and Materials Degradation doi: 10.3390/cmd7010016

Authors: Huda Alqahtani Amal El Tohamy Ahmed Aboelmagd Salah Rashwan Abdel Aziz Fouda Medhat Kamel

The N,N′-Bis(salicylidene)-1,3-propanediamine Schiff base (Salpn) was synthesized, characterized, and assessed as a corrosion inhibitor for low-carbon steel (LCS) in a 0.5 mol L−1 HCl solution. The study included chemical, electrochemical, and quantum mechanical methods to provide a comprehensive assessment. Experimental results revealed that the inhibition efficiency (IE) of Salpn increased with concentration, reaching a maximum of 69.1% at 300 ppm and 298 K, while a slight decrease to 64.3% was observed as the temperature increased. Tafel plot identified Salpn as a mixed-type inhibitor, while electrochemical impedance spectroscopy (EIS) revealed that the double layer capacitance decreased while the charge-transfer resistance increased as the concentration of Salpn increased. The thermodynamic study revealed that the adsorption of Salpn on the LCS surface follows the Langmuir isotherm model. The calculated standard free energy of adsorption (ΔG°ads) values ranged from −27.53 to −30.17 kJ mol−1, confirming that the inhibition process occurs via a mixed mechanism involving both physisorption and chemisorption. The presence of a protective film on the LCS surface was suggested by SEM observations, while EDX analysis showed an increase in C, O, and N signals, providing further indication of the inhibitor’s integration into the surface layer. Density functional tight-binding (DFTB+) calculations supported the high inhibitory performance by showing a low hardness value (0.091 eV). The compound’s high global softness (σ = 10.989 eV−1) suggested that it is an effective corrosion inhibitor. The Monte Carlo (MC) simulations demonstrated a strong interaction with a highly negative adsorption energy of −654.145 kJ mol−1. These findings collectively validate Salpn as an effective and strongly adsorbing corrosion inhibitor.

Corrosion and Materials Degradation doi: 10.3390/cmd7010015

Authors: Willian Aperador Giovany Orozco-Hernández Melquisedec Cortés-Zambrano

The present study evaluates the electrochemical behaviour of reinforcing steel embedded in an alkali-activated eco-cellular geopolymer concrete designed for applications in environments with high chloride exposure. The material was formulated using a ternary precursor composed of fluid catalytic cracking residue (FCC), Class F fly ash, and ground granulated blast furnace slag (BFS), activated with an alkaline solution and combined with preformed foam to generate a microstructure characterised by predominantly closed porosity and low capillary connectivity. The electrochemical response of the system was assessed through open circuit potential (OCP) measurements, Tafel polarisation curves, electrochemical impedance spectroscopy (EIS), and potentiodynamic tests under accelerated exposure to NaCl solutions. The results demonstrate a markedly improved electrochemical performance, evidenced by shifts in OCP towards more noble values, reductions of 45–65% in corrosion current density (Icorr), and increases of up to fourfold in charge transfer resistance (Rct), together with the development of broader and more stable passive regions. This behaviour is attributed to the synergistic interaction between the formation of dense N-(C)-A-S-H (sodium/calcium–aluminosilicate hydrate) and C-(A)-S-H (calcium–aluminosilicate hydrate) gels, the eco-cellular architecture with low capillary connectivity, and the stable high alkalinity of the activated matrix, which collectively restrict ionic transport and promote the passive stability of the reinforcing steel—defined here by noble OCP values, low Icorr, high Rct, and sustained passive domains in polarisation curves. Overall, the findings position the developed eco-cellular geopolymer concrete as a sustainable, high-performance alternative for infrastructure exposed to chloride-rich environments.

Corrosion and Materials Degradation doi: 10.3390/cmd7010014

Authors: Bohdan Efremenko Yuliia Chabak Ladislav Falat Vasily Efremenko Andriy Syrotyuk Ivan Petrišinec František Kromka Volodymyr Kulyk

The growing demand for hydrogen-based energy systems has intensified the need for structural materials with enhanced resistance to hydrogen-induced degradation. This study presents a comparative investigation of hydrogen-induced mechanical behavior and embrittlement susceptibility of laser powder bed fusion (LPBF) manufactured 316L steel and conventionally manufactured (CM) 316H steel. Tensile/Charpy testing, hydrogen charging (up to 115 h), OM, SEM, TEM, and EBSD analysis were employed to assess microstructure, strength, ductility, fracture characteristics, and phase stability. In the uncharged state, LPBF steel exhibited significantly higher strength but lower ductility than CM steel, attributed to its fine cellular sub-grain microstructure. Both steels showed similar hydrogen saturation kinetics, reaching ~9 ppm, with residual hydrogen levels of ~3.3 ppm after 90 days of desorption. Hydrogen exposure led to a more pronounced degradation of the tensile properties of the LPBF steel, with an up to 22% reduction in the ductility-based embrittlement index, while CM steel remained much less affected. Impact toughness in both materials resisted hydrogen embrittlement, retaining over 96% of initial values. Fractographic analysis of tensile specimens revealed subsurface brittle zones consistent with calculated hydrogen diffusion depths. EBSD data indicated that hydrogen-stabilized austenite in LPBF steel was achieved by suppressing deformation-induced martensitic transformation, despite increased dislocation activity. These findings suggest that, while LPBF steel is more vulnerable to hydrogen embrittlement under tensile loading via the HELP mechanism, its microstructure mitigates impact toughness degradation through hydrogen-induced austenite stabilization.

Corrosion and Materials Degradation doi: 10.3390/cmd7010013

Authors: Chathumini Samarawickrama Sebastian Pöhlker Qiushi Deng Paul White Patrick Keil Ivan Cole

This study investigates droplet-induced corrosion, a localized corrosion phenomenon driven by oxygen depletion within electrolyte droplets, distinct from bulk volume corrosion. To evaluate the performance of corrosion inhibitors under droplet conditions, a rapid screening electrochemical test method was employed, using a two-electrode setup to monitor corrosion currents. The study examined systematically different exposure environments including dissolved oxygen, pH, electrolyte molarity, and droplet geometry as key factors influencing atmospheric corrosion. Results show that dissolved oxygen levels significantly affect corrosion mechanisms, while larger droplets amplify the Evans droplet effect. Importantly, effective corrosion inhibitors mitigate this effect by reducing the cathodic reaction rate in droplet conditions. These findings advance the understanding of droplet corrosion mechanisms and provide insights into designing sustainable protection strategies to improve the longevity of steel structures in aggressive environments.

Corrosion and Materials Degradation doi: 10.3390/cmd7010012

Authors: Xingwei Hu Wangping Wu Ao Zhang Yu-Ao An Kunming Liu Danfeng Li

During industrial construction, steel measuring tapes are frequently exposed to alkaline cement environments, leading to rapid degradation of protective coatings and corrosion of the steel substrate. In this study, acrylic–amino resin composite coatings incorporating three different inhibitor systems (RZ/ZMP, RZ/ZPO, and RZ/ZPA) were prepared, and their corrosion resistance in alkaline media was systematically evaluated. The microstructure and composition of the coatings were characterized by SEM, EDS, and XRD, while surface wettability was assessed by water contact angle measurements. Corrosion protection performance was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and long-term alkaline immersion tests. The results show that the incorporation of inhibitors significantly enhances the corrosion resistance of the coatings. Compared with the inhibitor-free acrylic–amino resin coating, the corrosion current density of the RZ/ZPA coating decreases by approximately 1.9 times, while that of the RZ/ZPO coating decreases by about 1.7 times. EIS analysis further reveals that the RZ/ZPO/acrylic–amino resin coating exhibits the highest coating resistance (1.41 × 107 Ω·cm2), which is approximately 4.2 times higher than that of the inhibitor-free coating and 188 times higher than that of the steel substrate, indicating the strongest ion-blocking capability. Based on combined electrochemical parameters and long-term alkaline immersion behavior, the corrosion resistance of the coatings increases in the following order: acrylic–amino resin coating < RZ/ZPA < RZ/ZMP < RZ/ZPO. Overall, the synergistic effect of multiple inhibitors significantly improves both the electrochemical corrosion resistance and long-term alkaline durability of acrylic–amino resin coatings.

Corrosion and Materials Degradation doi: 10.3390/cmd7010011

Authors: Zouheir Morchid Elidrissi Meriyem Mouloudi Nabil Babassa Mohamed Essahli Mostafa Chhiba

Galvanic corrosion is an electrochemical phenomenon that arises due to the coupling of two different metals in an electrolytic environment, resulting in the deterioration of the less noble metal at an accelerated rate. This phenomenon poses a significant challenge in the economy of mixed-metal assemblies in many industrial applications due to the high maintenance and replacement expenditures that such systems incur. In this study, a stainless steel tube was galvanically coupled with a carbon steel fitting, and both were immersed in a chloride solution to study the galvanic interactions. The electrochemical processes associated with galvanic corrosion were simulated using a finite element multiphysics modeling approach (COMSOL Multiphysics). The simulations reproduced the metal–electrolyte interface potential and current density as well as the preferential anodic dissolution of carbon steel over stainless steel, which was observed during the coupled polarization. The numerical results matched the results predicted using assumptions for the steels’ electrochemical behavior. The results of the study confirmed that finite element simulation is an effective means of modeling galvanic corrosion and optimizing the design and life of metal component assemblies that are subjected to highly aggressive environments such as high-chloride environments. The numerical results matched the trends observed from experimentation and those previously reported in the literature and serve to provide qualitative and semi-quantitative insight regarding galvanic corrosion mechanisms instead of complete corrosion predictions regarding long-term corrosion behavior.

Corrosion and Materials Degradation doi: 10.3390/cmd7010010

Authors: Ainhoa Altube Estibaliz Rodríguez-Cambero Ana I. Viñuales Eva García-Lecina José Antonio Díez Hans Jürgen Grande

The present work aims to evaluate the electrochemical behaviour of 316L stainless steel flat sheets both uncoated and coated with an organic–inorganic silane hybrid formulation based on TEOS (tetraethyl orthosilicate) and TMES (Trimethylethoxysilane) as silane precursors. The influence of the modification of the silane-based layer by the incorporation of 3-aminopropyl trimethoxysilane (APS) doped TiO2 (N-TiO2) on the pitting properties of the coatings has been studied. The obtained protective films have been characterized from compositional (EDX), morphological (FE-SEM), and electrochemical (corrosion) points of view. Concerning their morphology, the coatings look continuous and smooth. Regarding their electrochemical properties, the results show that the application of the developed N-TiO2-containing silane coatings extends the passive potential range of 316L stainless steel in simulated body fluid; thus, it improves the pitting resistance of the substrate.

Corrosion and Materials Degradation doi: 10.3390/cmd7010009

Authors: Ihsan Ulhaq Toor

The formation and evolution of secondary phases, such as sigma (σ), chi (χ), Laves, carbides (M23C6), and nitrides (Cr2N), have a fundamental impact on the corrosion resistance of stainless steels. These stages alter the matrix’s local chemistry, compromise the passive film’s quality, and promote micro-galvanic interaction, which enhances localized corrosion issues. The thermodynamic stability, precipitation kinetics, and corrosion consequences of secondary phases in austenitic, ferritic, duplex, and lightweight (Fe–Mn–Al–C) stainless-steel systems are thoroughly reviewed and discussed in this paper. Advances in high-resolution characterization techniques, such as TEM, EBSD, atom-probe tomography, and in situ synchrotron techniques, have made it possible to map corrosion problems caused by secondary phases at the nanoscale. Computational thermodynamics (CALPHAD, DICTRA, TC-PRISMA) and emerging machine-learning models now provide quantitative prediction of phase formation and dissolution. Strategies for mitigation through alloy design, thermal treatment, and surface engineering are summarized, together with additive-manufacturing approaches for microstructural tailoring. Finally, this review highlights the integration of multi-scale modeling and sustainable alloy design to ensure phase-stable, corrosion-resistant stainless steels that enhance asset integrity and infrastructure reliability as per Sustainable Development Goals.

Corrosion and Materials Degradation doi: 10.3390/cmd7010008

Authors: Fraser King

It goes without saying that when studying the corrosion behaviour of a component or structure, the experimental conditions should reflect the service environment to which the object will be exposed. However, all too frequently, “accelerated” conditions are used, involving applied potentials, elevated temperature, high solute concentrations, excessive strain or strain rates, etc., which complicates the prediction of the in-service behaviour or component lifetime. At best, it is necessary to extrapolate the results of these accelerated laboratory measurements to more realistic conditions, ideally based on a mechanistic understanding of the processes involved. At worst, accelerated laboratory tests may suggest corrosion processes that are not feasible or relevant to the service environment, potentially disqualifying a given material or design from consideration that would otherwise provide acceptable behaviour in service. Examples of the need to properly take into account the service environment and the potential negative consequences of accelerated testing are given for the case of the corrosion behaviour of nuclear waste container materials. For example, the use of bulk solutions to study the corrosion of copper by sulfide in the laboratory involves high sulfide fluxes and leads to localized corrosion and stress corrosion cracking mechanisms that are not possible under actual repository conditions. Similarly, accelerating the effects of γ-irradiation using high absorbed dose rates runs the risk of changing the mechanism of radiation-induced corrosion. Above all, it is imperative to develop a sound mechanistic understanding of the underlying corrosion mechanisms in order to confidently apply the results of short-term laboratory observations to the prediction of the long-term performance of nuclear waste containers.

Corrosion and Materials Degradation doi: 10.3390/cmd7010007

Authors: Christofer Leygraf

I grew up in a home filled with music [...]

Corrosion and Materials Degradation doi: 10.3390/cmd7010006

Authors: Dominique Thierry Dan Persson Nathalie LeBozec

This paper is dedicated to long-term atmospheric corrosion behaviour of magnesium alloys. Five different magnesium alloys, namely, AZ31, AM60, AZ61, AZ80, and AZ91, were exposed for 4 years under harsh conditions at the marine corrosion site of Brest (France). From the results, the corrosion performance increased in the following order: AZ31 < AM60 < AZ91 < AZ61 < AZ80. The corrosion was highly localised during the first year of exposure, but more general corrosion prevailed after long-term exposure. All materials followed a power law with rather similar kinetics of corrosion. The observed difference in the corrosion performance of the alloys was explained by the amount of secondary phases as well as that of the Al-content in the α-Mg phase.

Corrosion and Materials Degradation doi: 10.3390/cmd7010005

Authors: Fynn Buhl Kilian Feil Nic Tusch André Korten Philipp Schempp

This study investigates the corrosion resistance of aluminum alloy AlSi10Mg to evaluate the influence of both manufacturing methods and heat treatments on its durability. The research compares samples produced via laser powder bed fusion (LPBF) and conventional casting, with subsets subjected to either no, T5 (artificial aging), and T6 (solution annealing and aging) heat treatment. All samples were exposed to an accelerated cyclic corrosion test, using immersion and drying cycles. Corrosion performance was quantified via mass loss (ML) measurements and analyzed using metallography. The analysis revealed that heat treatment (factor A) is the only statistically significant factor affecting mass loss. Even short exposure to the corrosive environment caused clearly visible surface changes. This suggests a significant decrease in corrosion resistance, linked to microstructural changes. While LPBF parts exhibited lower mass loss in the as-manufactured and T5 states, the T6 treatment negatively impacted both manufacturing routes.

Corrosion and Materials Degradation doi: 10.3390/cmd7010004

Authors: Tamim A. Samman Ahmed Gouda

This paper presents a validated, data-driven framework for the sustainable rehabilitation of corrosion-damaged marine infrastructure, demonstrated through a comprehensive study on a historic coastal structure. The implemented three-phase methodology—integrating advanced condition assessment, evidence-based intervention design, and rigorous performance validation—successfully addressed severe chloride-induced deterioration. Diagnostic quantification revealed that 30% of the primary substructure was severely compromised, with chloride concentrations reaching 1.94% by weight (970% above the corrosion threshold) and half-cell potential mapping confirming a >90% probability of active corrosion in critical elements. Guided by this data, a synergistic intervention combining galvanic cathodic protection, high-performance coatings, and structural strengthening was deployed. Post-repair validation confirmed exceptional outcomes: a complete electrochemical repassivation (potential shift from −385 mV to −185 mV), a 97.3% reduction in chloride diffusion rates, a 250% increase in surface resistivity, and the restoration of structural capacity to 115% of design specifications. The framework achieved a 65% reduction in projected lifecycle costs while establishing a new paradigm for preserving marine infrastructure through evidence-based, multi-mechanism strategies that ensure long-term durability and economic viability.

Corrosion and Materials Degradation doi: 10.3390/cmd7010003

Authors: Denis Nazarov Lada Kozlova Vladislava Vartiajnen Sergey Kirichenko Maria Rytova Anton P. Godun Maxim Maximov Arina Ilina Stephanie E. Combs Mark Pitkin Maxim Shevtsov

Research into methods for regulating the biocorrosion rate of biodegradable magnesium implants is one of the most urgent tasks in the field of biomedical materials science. Atomic layer deposition (ALD) is a highly effective method for the preparation of nanocoatings, which can be used to regulate the biodegradation rate. The present paper presents the findings of a research study in which the most commonly used simple oxide ALD coatings (Al2O3, TiO2, and ZnO) were examined, in addition to mixed coatings obtained by alternating ALD cycles of the application of ZnO-TiO2 (ZTO) and Al2O3-TiO2 (ATO). The coating thicknesses exhibited a variation within the most typical range for ALD coatings, measuring between 20 and 80 nanometres. The biocorrosion testing was conducted in Ringer’s physiological solution through the measurement of potentiodynamic polarisation curves and impedance spectroscopy. The findings demonstrated that, for Al2O3 coatings, the protective properties exhibited an increase with increasing thickness, while for TiO2, the trend was found to be dependent on the type of precursor utilised. The protective properties of titanium tetraisopropoxide (TTIP) have been observed to increase with increasing thickness. Conversely, the protective properties of titanium tetrachloride (TiCl4) have been observed to decrease. The application of mixed ZTO oxides with a thickness of 40 nm has been demonstrated to reduce the corrosion current by 1.7 and 3.4 times, depending on the use of TiCl4 or TTIP. Furthermore, the effectiveness of ATO coatings of similar thicknesses has been shown to be higher, with a reduction in corrosion currents of 54 and 24 times for samples obtained using TiCl4 and TTIP, respectively. A thorough analysis of the collected data unequivocally demonstrates the superior efficacy of mixed oxides in comparison to their pure oxide counterparts.

Corrosion and Materials Degradation doi: 10.3390/cmd7010002

Authors: Kateryna Popova Jan Švadlena Tomáš Prošek

Rubber components filled with carbon black are widely used in vehicles for sealing, preventing water ingress, and reducing vibration and aerodynamic noise. However, carbon particles increase the electrical conductivity of rubber. When a carbon-filled rubber part comes into contact with the metal car body, it may act as a cathode, accelerating metal corrosion via galvanic coupling. This study combined volume resistivity and zero-resistance ammeter (ZRA) measurements, resistometric corrosion monitoring, and accelerated corrosion testing to assess the effect of rubber conductivity on the corrosion degradation of painted car body panels in defects. More conductive rubber induced a higher galvanic current and accelerated paint delamination from defects. Real-time monitoring confirmed an earlier onset of corrosion and higher corrosion rates for steel coupled with conductive rubber. These findings emphasize the importance of using low-conductive rubber with resistivity from 104 Ω·m to minimize the risk of galvanic corrosion of the car body.

Corrosion and Materials Degradation doi: 10.3390/cmd7010001

Authors: Andri Isak Thorhallsson Erlend Oddvin Straume Tomaso Maccio Erfan Abedi Esfahani Helen Osk Haraldsdottir Lilja Tryggvadottir Sigrun Nanna Karlsdottir

Currently, there are several deep drill geothermal projects that aim to discharge superheated or supercritical geothermal fluid for sustainable power production. In geothermal power utilisation, the well casing steel and surface equipment is susceptible to corrosion due to corrosive species in the geothermal fluid. The temperature and the phase state of the fluid greatly affect the extent and the forms of corrosion that can occur. To mitigate corrosion damage in the casing and surface equipment, the recently developed production method Extra High-speed Laser Application (EHLA) cladding is proposed as a solution. To simulate application of carbon steel and EHLA clads in superheated geothermal wells, the materials were tested in a superheated steam containing CO2 and H2S at 450 °C temperature and 150 barG pressure. Microstructural and chemical analysis was performed with SEM, EDX and XRD, and corrosion rate was analysed with the weight loss method. The carbon steel was prone to corrosion with a double corrosion layer but the corrosion of the EHLA clads was insignificant. The results show that the EHLA clads tested have good corrosion resistance in the test environment, and the study can aid in the selection of casing and clad materials for future deep geothermal wells. Furthermore, this study shows that the EHLA clads increase the variety of corrosion mitigation solutions for future geothermal projects.

Corrosion and Materials Degradation doi: 10.3390/cmd6040067

Authors: Willian Aperador Giovany Orozco-Hernández Jonnathan Aperador

This study evaluated the efficacy of an environmentally friendly degreasing agent formulated from orange peel extract as both a cleaning agent and corrosion inhibitor for surgical instruments manufactured from 316LVM stainless steel. The extract was obtained via microwave-assisted hydrodistillation and subsequently blended with biodegradable surfactants. Its performance was compared against a benchmark commercial cleaner (West Oxyclean®) through Tafel polarization, Electrochemical Impedance Spectroscopy (EIS), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-Ray Diffraction (XRD). FTIR analysis confirmed the presence of terpenic compounds, predominantly limonene, alongside ethers, alcohols, and unsaturated structure characteristics of citrus essential oils. Polarization and EIS results showed that the formulation containing 0.12% extract exhibited the highest charge-transfer resistance and the lowest corrosion current density (0.093 μA/cm2), achieving an inhibition efficiency of 81.29%, whereas the 0.08% formulation showed greater corrosive response than the commercial cleaner. SEM imaging demonstrated a progressive decline in both the severity and density of localized corrosion attacks with increasing extract concentration, while XRD diffractograms indicated a marked reduction in corrosion-product formation—completely absent at the optimal concentration. These findings demonstrate that orange peel extract functions as an effective and environmentally sustainable corrosion inhibitor, capable of preserving the structural and surface integrity of surgical-grade steel. Its technical performance, combined with its biodegradable profile, positions it as a promising alternative to conventional industrial cleaners within medical and hospital applications.

Corrosion and Materials Degradation doi: 10.3390/cmd6040066

Authors: Chiara Petiti Marco Faifer Irena Todua Sergio Toscani Jaime J. H. Henriquez Sara Goidanich

Electrical resistance (ER) sensors are established tools for monitoring atmospheric corrosion in real time, yet their application to cultural heritage requires adaptation to the complex stratigraphy of patinated surfaces. In this work, customised ER sensors were optimised to allow the sensors to be pre-patinated, enabling a more realistic simulation of corroded heritage metals. Different geometries and artificial patinas were applied to assess sensitivity, robustness, and representativeness under variable environmental conditions. The study confirms the decisive role of corrosion layers in shaping sensor response and highlights the potentialities of pre-patinated ER sensors as realistic mock-ups for testing conservation strategies and evaluating environmental corrosivity under conditions relevant to cultural heritage preservation.

Corrosion and Materials Degradation doi: 10.3390/cmd6040065

Authors: Andri Isak Thorhallsson Gunnar Skulason Kaldal Thorri Jokull Thorsteinsson Deirdre Elizabeth Clark Erfan Abedi Esfahani Tomaso Maccio Helen Osk Haraldsdottir Lilja Tryggvadottir

Carbon steel casing material in high-temperature deep geothermal wells can be prone to severe corrosion and premature failure due to the oxidation capacity of H2O, H2S, CO2, and more corrosive species in geothermal fluid. Due to the higher temperature and pressure and phase state of fluid in high-temperature deep geothermal wells, the rate and extent of corrosion can be expected to be different than in low-temperature geothermal wells. To reduce the extent of corrosion damage and corrosion rate, and increase the lifetime of geothermal wells, one mitigation method is to clad the internal surface of the geothermal casing with a more noble, corrosion-resistant material. Conventional cladding, however, has been an expensive and time-consuming process up to the current date, but recently, a more economical and productive method has been established, i.e., EHLA cladding. In this study, a 14-day corrosion performance test was conducted on stainless steel and nickel-based alloy clads on a carbon steel substrate in a 262 °C and 95 bar geothermal well in the Hellisheidi geothermal field (SW Iceland). Samples were partially or fully cladded, and some samples were stressed to investigate the clads’ susceptibility to general corrosion and stress corrosion cracking, as well as the substrate’s vulnerability to galvanic corrosion. Corrosion analysis of pure carbon steel substrate was also investigated for comparison. Samples were microstructurally analysed with SEM, and chemical analysis was performed with EDX. The results indicated that the clad materials have good corrosion resistance in the geothermal environment tested, suggesting that EHLA cladding is a more feasible option for strengthening the corrosion resistance of geothermal casing and equipment.

Corrosion and Materials Degradation doi: 10.3390/cmd6040064

Authors: John Paulo M. Serwelas Seong-Hoon Kee Cris Edward F. Monjardin Kevin Paolo V. Robles

This study examines the relationship between bond strength degradation in corroded reinforced concrete and Half-Cell Potential (HCP) measurements through a combined experimental and numerical approach. Fifty-four concrete specimens reinforced with D19 and D22 rebars underwent impressed-current corrosion to induce specific levels of mass loss. The experimental results showed a progressive reduction in bond strength with increasing corrosion; at approximately 20% mass loss, D19 specimens exhibited up to ~45% reduction, while D22 specimens showed a reduction in ~30%. Correspondingly, HCP values became more negative as corrosion intensified, shifting from around −200 mV at 0% corrosion to values below −900 mV at higher corrosion levels. Although HCP effectively reflected corrosion severity, it did not correlate linearly with bond strength degradation. Numerical simulations performed using COMSOL Multiphysics reproduced the observed electrochemical trends, demonstrating increasingly negative potential distributions with higher corrosion current densities. The findings confirm that HCP is a reliable indicator of corrosion activity but has limited predictive capacity for bond strength loss. This work contributes quantitative insight into the electrochemical–mechanical relationship in corroded reinforced concrete and supports the development of improved assessment frameworks for early maintenance and structural integrity evaluation.

Corrosion and Materials Degradation doi: 10.3390/cmd6040063

Authors: Saman Hosseinpour Sukanya Hägg Mameng Marie Almen Mia Liimatainen

Owing to its corrosion resistance, stainless steel is a sustainable alternative to carbon steel as a structural material in challenging seawater environments. Studies on carbon steel indicate that among all marine corrosion zones (i.e., atmospheric zone, splash zone, tidal zone, and immersed zone), the rate of corrosion is particularly high in the splash zone, above the seawater level, due to the recurrent splashing of seawater with high levels of oxygen and chloride content. Nevertheless, the information on the extent of localized corrosion (i.e., pitting and crevice corrosion) on stainless steel in the splash and tidal zones is scarce and, in most cases, limited to standard austenitic grades. In this work, we present the pitting and crevice corrosion results on lean duplex, duplex, and super duplex stainless steels after two years of field exposure in the North Sea (site at Heligoland South Harbour). The standard austenitic grade 1.4404 (316L) was also exposed as a reference material in atmosphere and splash zone conditions. Parallel exposure of coupons in splash, tidal, and immersed zones allows comparison of the extent of corrosion in each zone and enables proper material selection for structural applications in marine environments.

Corrosion and Materials Degradation doi: 10.3390/cmd6040062

Authors: Gregory Neizvestny Samuel Kenig Konstantin Kovler

The aging of three-layer polyethylene-coated buried steel pipelines for oil/gas and water transport poses significant challenges for public safety, environmental integrity, and economic sustainability. Over time, these pipelines become increasingly susceptible to corrosion and eventual failures, which can pose environmental hazards, safety risks, and costly repairs. Consequently, predicting the service life of polyethylene-coated steel pipelines is critical for mitigating corrosion risks, extending operational lifespan, and planning effective maintenance strategies. Current international standards lack clear methodologies and criteria for assessing the aging behavior of polyethylene-coated underground pipelines. Current studies have examined two techniques—Line Current Attenuation (LCA) and Drainage Test (DT)—to estimate aging rates in polyolefin-coated pipelines following soil exposure during service. The present study introduces an innovative approach for evaluating aging behavior. It includes a comprehensive analysis using an exponential aging model to estimate the coating’s average specific electrical resistance at any service time, as well as quantitative criteria for the failure of oil/gas and water pipelines. Moreover, it is based on the modified LCA as the most suitable aging methodology with some limitations. Finally, the study concludes with a derived correlation between the coating’s initial specific electrical resistance and its aging rates, and the prediction of the residual life of the polyethylene coating. This integrated framework provides a robust foundation for regulatory bodies, design engineers, maintenance planners, quality assurance/control teams, and researchers to ensure the long-term integrity and sustainability of underground polyethylene-coated steel pipelines.

Corrosion and Materials Degradation doi: 10.3390/cmd6040061

Authors: James Lelliott Elizabeth Sackett Neil McMurray Douglas Figueroa-Gordon

The adoption of advanced high-strength steels (AHSS) in the automotive industry has significantly increased in recent years driven by weight reduction and enhanced crashworthiness. Hot dip galvanised sacrificial coatings are regularly applied to these steels for corrosion protection. In this investigation, the scanning vibrating electrode technique (SVET) demonstrated that hydrogen evolution on the steel substrate is taking place when these sacrificial coatings are damaged during service, increasing the risk of hydrogen embrittlement. The hydrogen embrittlement susceptibility of a new generation of nano-precipitate ferritic, FNP, AHSS have been studied and compared against conventional dual phase ferritic-martensitic, FM, AHSS at equivalent strength levels. Hydrogen permeation tests have shown that FNP AHSS have lower effective diffusion coefficients, Deff, than FM AHSS at equivalent strength levels. At 800 MPa strength levels Deff were 1.68 × 10−7 cm2/s and 1.87 × 10−7 cm2/s for FNP800 and FM800, respectively. At higher strength levels, 1000 MPa, Deff were 7.45 × 10−8 cm2/s and 1.45 × 10−7 cm2/s for the FNP1000 and FM1000, respectively. Slow strain-rate tests (SSRT) showed that FNP AHSS displayed over 35% higher resistance to hydrogen embrittlement than conventional FM AHSS. Quantitative fractographic analyses confirmed that the new ferritic nano-precipitate microstructure retains much more ductile behaviour than conventional martensitic-ferritic even under the most severe hydrogen charging conditions tested.

Corrosion and Materials Degradation doi: 10.3390/cmd6040060

Authors: Chuyuan Cui Yongsheng An Xiangpeng Wang Ping Qiu

Inspired by the mechanism of ion exchange resins, this study is a first-report in constructing a dual-layer photocathodic protective coating with ionic selectivity to enhance corrosion resistance property. The microstructure, composition, and ion selectivity of the coating are characterized by scanning electron microscopy, Raman spectroscopy, infrared spectroscopy, and membrane potential. It shows that the outer g-C3N4/TiO2 cation-selective layer plays a role in preventing corrosive Cl− ions passing through the coating; the inner g-C3N4-TiO2-CTAB anion-selective layer could prevent Fe2+ ions from diffusing through the coating. Furthermore, the coated carbon steel sample demonstrates a minimum OCP (open circuit potential) value of −770 mV (vs. SCE) under illumination in 3.5% NaCl media. Interestingly, the OCP remains around −720 mV (vs. SCE) even after light deprivation. The synergistic effect between ion selectivity and photocathodic protection is described, in detail, in the following.

Corrosion and Materials Degradation doi: 10.3390/cmd6040059

Authors: Dan Persson Alexander Wärnheim Nathalie LeBozec Dominique Thierry

The initial formation of corrosion products in pure humid air on magnesium alloys AZ91 and AZ31 was studied using infrared reflection absorption spectroscopy (IRRAS), infrared spectroscopic imaging, and SEM-EDS. The kinetics of corrosion product formation were monitored in situ with IRRAS during exposure to humid air (95% relative humidity) under two different CO2 concentrations: low (≤1 ppm) and ambient (400 ppm). For low CO2 concentrations, the primary corrosion product detected on both alloys was magnesium hydroxide (Mg(OH)2). In contrast, under ambient CO2 conditions (400 ppm), magnesium hydroxy carbonate was the dominant product. After 16 h of exposure, the amount of magnesium converted into corrosion products was approximately 8–10 times higher under low-CO2 conditions compared to ambient levels. The smaller formation of corrosion products but increased magnesium carbonate formation on AZ91D is attributed to its higher aluminium content compared to AZ31. Corrosion attack and product formation were largely localised to the centre of the α-phase in AZ91D, with the β-phase likely serving as sites for cathodic reactions.

Corrosion and Materials Degradation doi: 10.3390/cmd6040058

Authors: Mohammad Reza Attar Ali Davoodi

Corrosion is a complex, surface-initiated process that demands nanoscale, real-time characterization to understand its initiation and propagation. Atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) have emerged as powerful tools in corrosion science, enabling high-resolution imaging and electrochemical mapping under realistic conditions. This review, inspired by pioneering work at KTH by Professors Christofer Leygraf and Jinshan Pan, highlights advanced analytical strategies that extend the capabilities of AFM and SKPFM beyond traditional line-profile analysis. Techniques such as power spectral density (PSD) analysis, multimodal Gaussian histogram fitting, statistical roughness quantification, and deconvolution methods are discussed in the context of case studies on aluminum alloys, stainless steels, magnesium alloys, biomedical implants, and protective coatings. By integrating in situ imaging, electrochemical mapping, and statistical data processing, these approaches provide deeper insights into localized corrosion, micro-galvanic coupling, and surface reactivity. Future directions include coupling AFM-based methods with high-speed imaging, machine learning, and spectro-electrochemical techniques to accelerate the development of corrosion-resistant materials and enable probabilistic diagnostics of corrosion initiation susceptibility.

Corrosion and Materials Degradation doi: 10.3390/cmd6040057

Authors: Shuhui Chen Bao Chen Min Liu Ji Liu Gen Li Ying Jin

To address the premature corrosion failure of chromium-based coatings in harsh environments (e.g., high temperatures, chloride-containing solutions), this work systematically investigates how rare-earth (RE, i.e., Ce and La) elements regulate nitrogen (N) adsorption and diffusion behavior in Cr during the early stages of nitriding, a critical corrosion protection strategy, using first-principles density functional theory (DFT). Results show that RE preferentially occupies Cr substitutional site, increasing the Young’s modulus from 293.5 GPa (pristine Cr) to 344.9 GPa (Ce-doped) and 348.7 GPa (La-doped). Surface RE doping on Cr(110) significantly enhances N adsorption energy from −3.23 eV to −3.559/−3.645 eV (Ce-/La-doped), whereas subsurface doping slightly weakens the adsorption. Moreover, the energy barrier for N penetration into subsurface is reduced from 2.11 eV to 2.03/1.91 eV (Ce-/La-doped), thereby facilitating nitridation. Notably, RE is found to strongly trap vacancies and N atoms, leading to increased migration barriers and thus hindering their long-range transport. These findings demonstrate that RE exhibits a dual role during nitriding: promoting N incorporation at the surface while restricting its deep diffusion into the bulk. The study provides theoretical insights into the atomistic mechanisms by which RE elements modulate nitriding efficiency in Cr-based alloys, offering guidance for the design of RE-doped surface-modified coatings with improved corrosion resistance.

Corrosion and Materials Degradation doi: 10.3390/cmd6040056

Authors: Jinshan Pan

The spontaneous formation and stability of a protective passive film on a metal surface are crucial for the metal material’s corrosion resistance during its service life. Passive films have been extensively studied, and our understanding of passive films has been significantly improved with the development of advanced analytical techniques. Modern synchrotron X-ray sources offer unprecedented possibilities for detailed analyses of passive films and for in situ and operando studies of passive films in both gaseous/aqueous environments, as well as in electrochemical environments. This mini review presents a short summary of recent studies on passive films, mainly focusing on stainless steels and nickel-base alloys, which utilize state-of-the-art synchrotron X-ray techniques, particularly X-ray photoelectron spectroscopy (XPS), often in combination with other synchrotron techniques such as X-ray adsorption, diffraction, reflectivity, and fluorescence. These reports demonstrate that synchrotron-based techniques greatly improve probing sensitivity and spatial resolution, enabling in situ and operando studies of passive films at solid–liquid interfaces. These studies reveal changes in the passive film and underlying alloy layer, highlighting the important role of hydroxides, as well as the inhomogeneity in passive films associated with the complex microstructures in advanced industrial alloys.

Corrosion and Materials Degradation doi: 10.3390/cmd6040055

Authors: Valentin Chukhin Nikolay Makisha Igor Gulshin

This paper presents comprehensive studies of pitting corrosion, which precedes the appearance of fistulas in galvanized steel pipelines of hot and cold water supply systems. Corroded galvanized pipes taken out from water supply systems within their operation and scale samples were the subject of this research. The current work continues the research on one of the four structural elements of tubercles—the dense layer. The corrosion of the zinc coating and the steel base of pipes inside the tubercles led to a gradual increase in the concentration of a solution containing components of the corroding metal (zinc and iron cations) and anions in water (mainly chlorides and sulfates). To explain the corrosion under the tubercles, their dense layer was compared with an anion exchange membrane with selective properties, which provided the primary concentration of the salt solution in the structure of the tubercles with a significant increase in the concentration of aggressive anions compared to the source water. The formation of fistulas in the cavity leads to a secondary concentration of solution inside the tubercle, mainly consisting of iron chloride. At the same time, due to the hydrolysis of the formed iron salts and a decrease in pH, the corrosion rate increases and becomes independent of external conditions. This article summarizes ten years of experience in examining corrosion of steel pipes from external and internal water supply systems.

Corrosion and Materials Degradation doi: 10.3390/cmd6040054

Authors: Johan Tidblad Alice Moya Núñez Daniel de la Fuente Gino Ebell Tore Flatlandsmo Berglen Terje Grøntoft Ulrik Hans Ioannis Christodoulakis Daniel Kajánek Kateřina Kreislová Lech Kwiatkowski Teresa La Torreta Rafał Lutze Guadalupe Pinar Larrubia Valentina Pintus Michael Prange Pasquale Spezzano Costas Varotsos Aurélie Verney-Carron Tiina Vuorio Tim Yates

This paper reviews results published by the International Co-operative Programme on Effects on Materials including Historic and Cultural Monuments (ICP Materials) with emphasis on those obtained after the turn of the century. Data from ICP Materials come from two main sources. The first is through exposures of materials and collection of environmental data in a network of atmospheric exposure test sites mainly distributed across Europe. Corrosion of carbon steel has continued to decrease during the period 2000–2020 but corrosion of zinc only up until 2014, and the trend in zinc corrosion is only visible when examining four-year data. Surface recession of limestone as well as soiling of modern glass show no decreasing trend during 2000–2020. The second is through case studies performed at heritage sites across Europe. Risk analysis of corrosion and soiling for twenty-six sites indicate that currently soiling is a more significant maintenance trigger than corrosion. Costs for maintaining heritage sites are substantial and costs attributable to air pollution is estimated from 40% to as much as 80% of the total cost. Future directions of the program are work on effects of particulate matter, improving the scientific basis for the work, and making the monitoring data publicly available.

Corrosion and Materials Degradation doi: 10.3390/cmd6040053

Authors: Wenchao Li Shilong Chen Hui Xiao Xiaofei Jiao Yurong Wang Shuwei Song Songtao Yan Ying Jin

Atmospheric corrosion in sand dust environments is driven by deposits that bear chloride, which sustain thin electrolyte layers on metal surfaces. We established a laboratory protocol to replicate this by extracting, formulating, and depositing a preliminary layer of mixed salts from natural dust onto samples, with humidity precisely set using the salt’s deliquescence behavior. Degradation was tracked with SEM/EDS, 3D profilometry, XRD, and electrochemical analysis. Bare steel showed progressive yet decelerating attack as rust evolved from discrete islands to a lamellar network; while this densification limited transport, its internal cracks and interfacial gaps trapped chlorides, sustaining activity beneath the rust. In contrast, QPQ-treated steel remained largely protected, with damage localized at coating defects as raised rust nodules, while intact regions maintained low electrochemical activity. By coupling salt chemistries derived from the field with humidity control guided by deliquescence and diagnostics across multiple scales, this study provides a reproducible laboratory pathway to predict atmospheric corrosion.

Corrosion and Materials Degradation doi: 10.3390/cmd6040052

Authors: Faiza Kakaa Mosbah Ferkhi Ammar Khaled Sabah Amira Marielle Eyraud

This work investigates and compare the corrosion behavior in artificial saliva of oxide thin films grown on commercially pure titanium (cp-Ti), via electrochemical oxidation (EO) in sulphate bath at 1 V and thermal treatment (TT) at 450 °C, for durations between 20 min and 4 h. The goal is to determine which method and duration provide the optimal protection for titanium against degradation in dental environment particularly in varying fluoride concentration and acidity. Surface characterizations were performed through morphological and microstructural analysis using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical behavior was conducted in Fusayama-Meyer solution (pH = 6.50 and T = 37 °C) using potentiodynamic polarization curve (PPC) and electrochemical impedance spectroscopy (EIS), under varying pH and fluoride ion concentrations. The results demonstrated that a 3-h duration treatment provided the optimal corrosion resistance for both EO and TT processes. The pH of the environment influenced corrosion performance markedly: both acidic (pH 2.5) and basic (pH 9.0) conditions increased Icorr and decreased Rp, indicating degradation of the passive oxide layer outside neutral conditions. Similarly, increasing fluoride concentrations (1000; 5000; and 12,300 ppm) significantly impaired corrosion resistance. At 12,300 ppm F−, untreated Ti showed severe degradation, with EIS revealing the formation of a porous outer layer and a weakened inner barrier layer (Rf = 33 W·cm2 for the outer layer and Rct = 21 kW·cm2 for the barrier layer). In contrast, the TT-treated surface remained highly protective even under these aggressive conditions, with minimal surface damage and the highest resistances for both the outer and the inner layers (Rf = 1610 kW·cm2; Rct = 1583 kW·cm2), significantly outperforming the EO film. These findings highlight the superior performance of thermal oxidation at 450 °C for 3 h as a promising surface treatment for enhancing the corrosion resistance of titanium in fluoride-rich oral environments. Understanding these strategies helps improve the longevity and security of titanium dental implants.

Corrosion and Materials Degradation doi: 10.3390/cmd6040051

Authors: Inger Odnevall Gunilla Herting

The use of copper and its alloys in architecture, especially in arid regions, is growing, driven by visual appeal, functional advantages, and sustainability. Changes in visual and colorimetric appearances and patina formation were evaluated for architectural Cu metal, brass (CuZn15), bronze (CuSn4), and a golden alloy (CuZn5Al5). Coupons were exposed over 4 years in Dubai, United Arab Emirates, at a test site located 2 km from the seashore under unsheltered conditions, and at various surface inclinations. Comparative exposures were conducted in Brest, France, at sites of increasing distance from the seashore. Visual appearance was assessed by colorimetry and optical imaging; patina cross-sections were characterized by means of scanning electron microscopy and elemental analysis (SEM/EDS), and crystalline phase identification was conducted by means of x-ray diffraction (XRD). All Dubai surfaces developed red-yellowish, heterogeneous patinas with embedded sand and dust, reducing lightness and visual appeal. Inclination had minor effect, although some extent of spallation occurred on downward-facing CuSn4. Even the corrosion-resistant CuZn5Al5 alloy lost its golden hue due to the incorporation of sand and dust into the patina. In Brest, appearance depended on the distance from the seashore, with green-blue patinas near the sea and red-yellowish farther inland, similar to Dubai. Cleaning may restore some luster, but the desert exposure generally reduced the long-term aesthetic performance of all materials.

Corrosion and Materials Degradation doi: 10.3390/cmd6040050

Authors: Jiao Meng Xingyu Li Feng Guo Wenhua Cheng Ruiling Jia

In 3.5 wt% NaCl solution used to simulate seawater, the individual (self-corrosion) and coupled (galvanic) corrosion behaviors of TA22 titanium alloy and 304 stainless steel were systematically investigated at 25 °C, 35 °C, 45 °C and 55 °C. Post-corrosion surfaces were characterized by scanning electron microscopy (SEM), three-dimensional profilometry and X-ray photoelectron spectroscopy (XPS). The results demonstrated that elevating temperature decreased the compactness and protective quality of the passive film on both alloys, as indicated by increasing donor densities and positive shifts in flat-band potentials. Distinct pitting corrosion occurred on 304 SS above 45 °C. Upon galvanic coupling, the passive film on TA22 was modified in both structure and composition, exhibiting a decreased TiO2 content and increased lower valence oxides (Ti2O3, TiO). The galvanic effect intensified with temperature, leading to progressively aggravated corrosion of 304 SS, characterized by increased pit density, diameter, and depth compared to its self-corrosion state.

Corrosion and Materials Degradation doi: 10.3390/cmd6040049

Authors: Hongyi Hu Xian Zhang Tianyou Huang Rui Yu Kaiming Wu

In concentrated solar power (CSP) systems, structural materials face severe corrosion challenges induced by molten chlorides, with the corrosion severity being highly dependent on the salt composition. This study systematically compares the corrosion behavior of two representative superalloys, Inconel 625 and SS321, in binary NaCl–KCl and ternary MgCl2–NaCl–KCl molten salts at 700 °C. The corrosion products and microstructural features were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD), in combination with static exposure tests to elucidate the underlying mechanisms. The results show that in NaCl–KCl molten salts, both alloys primarily form Cr2O3 as the protective product. However, the corrosion scale of SS321 is porous, whereas Inconel 625 develops a dense NiCr2O4 inner layer, exhibiting superior corrosion resistance. In the MgCl2–NaCl–KCl molten salt system, Cr2O3 is replaced by a dense MgO layer forms on Inconel 625, coupled with Mo surface enrichment, which significantly inhibits Cr depletion and leads to a notably reduced corrosion rate relative to the binary salt. In contrast, the transformation of Cr2O3 on SS321 into porous MgCr2O4 exacerbates intergranular corrosion, resulting in a substantial degradation of corrosion resistance. This study elucidates the distinct corrosion pathways and mechanisms of different alloys in binary and ternary chloride salts, providing important guidance for the selection of molten salt compositions and corrosion-resistant structural materials in CSP applications.

Corrosion and Materials Degradation doi: 10.3390/cmd6040048

Authors: Mats Ahmadi Götelid Sareh Ahmadi Götelid Saman Hosseinpour Christofer Leygraf C. Magnus Johnson

Self-assembled monolayers of alkane thiolate and alkane selenolate have been proven to inhibit atmospheric corrosion, but upon prolonged exposure to the important constituents of indoor atmosphere, namely humidified air with formic acid, the protective layer eventually breaks, but the exact reason is not yet clear. In this paper, we report on an XPS study of co-adsorbed formic acid and hexane selenol on a Cu surface. Adsorption of hexane selenol at room temperature breaks the Se-C bond, leaving a monolayer of Se on the surface, whereas adsorption at 140 K leaves a layer of selenolate. Formic acid exposure to the selenolate-Cu surface leads to adsorbed formate on unprotected areas and absorption of formic acid within the alkane chain network. During heating, the formic acid desorbs and the Se-C bond breaks, but formic acid does not accelerate the Se-C scission, which occurs just below room temperature both with and without formic acid. Thus, formic acid alone does not affect the Se-C bond, but its presence may create disorder and open up the alkane carpet for other species. Selenol removes formate and oxide from the surface at room temperature. The Se-C bond breaks and the alkane chain reacts with surface oxygen to form carbon oxides and volatile hydrocarbons.

Corrosion and Materials Degradation doi: 10.3390/cmd6040047

Authors: Sedigheh Rashidi Arnab Chatterjee Amit Pandey Rajeev K. Gupta

High-temperature oxidation behavior of an alumina-forming austenitic stainless steel (AFA25) produced by additive manufacturing (AM) has been studied at 850 °C in air and compared to the conventional wrought alloy. The mass gain measurements during high-temperature oxidation tests were performed to understand the rate of oxidation, oxidation characteristics, and morphology of oxides that form in these alloys. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to characterize the microstructure and oxide scale formation during high-temperature exposure. A similar alumina scale was observed on both wrought and AM alloys. The continuous alumina layer that forms in these alloys provides superior oxidation resistance. This paper shows that a variation in AM build parameters influences the oxidation properties, where one AM alloy with a lower laser power to hatch ratio depicts much better oxidation properties compared to conventional wrought AFA alloys.

Corrosion and Materials Degradation doi: 10.3390/cmd6040046

Authors: Robert E. Melchers

Calcareous deposits on and within corrosion products tend to inhibit the (abiotic) corrosion of steels in seawater. Herein, it was considered whether this inhibition effect extends to microbiologically influenced corrosion (MIC) for extended (long-term) exposure periods. Quantitative estimates of corrosion rates were made from reported observations for 46 iron and steel shipwrecks, and other iron and steel objects immersed in seawater at various depths and for extended periods (many around 60 years and some up to 160 years). The observations are correlated with observations of the occurrence of calcareous deposits and information about dissolved inorganic nitrogen (DIN), a critical micronutrient for MIC. The results show that calcareous deposits can inhibit both long-term abiotic corrosion and long-term corrosion influenced by conditions suitable for MIC. The practical implications are briefly reviewed.

Corrosion and Materials Degradation doi: 10.3390/cmd6030045

Authors: Adrian Marx Dennis Hülsbruch Jochen Ströhle Bernd Epple

High-temperature corrosion is a frequently observed phenomenon in waste incineration facilities. Municipal solid waste presents substantial corrosion potential attributed to elevated chlorine content and significant inhomogeneity in calorific value and chemical composition, rendering stable plant operation and corrosion control challenging. Conventional countermeasures, such as cladding or reduced steam parameters, lack temporal resolution and incur substantial costs or reduced efficiency. For this study, a waste incineration plant was equipped with an online corrosion monitoring system featuring ten sensors distributed across three vertical boiler passes. The system employs an electrochemical measurement principle to enable the detection of corrosion with temporal resolution. The recorded data reveals decreasing corrosion attack and increasingly stable deposits along the flue gas path. Combined with the temperature measurements, the sensor data proves the effectiveness of the shower cleaning in the third pass and confirms successful removal of the deposits. Statistical analysis shows a correlation between CO content and sensor data, while other parameters (e.g., steam flow, flue gas temperatures) exhibit no conclusive correlations, emphasizing the system’s added value. Chemical analysis of the electrodes and deposits reveal significant indications of chlorine and sulfur, suggesting chlorine-catalyzed active oxidation as the predominant corrosion mechanism.

Corrosion and Materials Degradation doi: 10.3390/cmd6030044

Authors: Robert Jeffrey Robert E. Melchers

Comprehensive data are presented for corrosion losses of mild steel exposed for up to 5 years, all obtained from exposing steel coupons at one specific severe marine exposure site on the Pacific Ocean coast. The test programme considered the effects of duration of exposure, inclination, orientation, height, shielding, and coupon variability, using multiple, nominally identical mild steel coupons, all under a single local climatic regime. Such a controlled, consistent, natural environment permits unique, valid comparison of the various influences, both for short-term and longer-term exposures, unlike previous tests of some parameters conducted in the short term at disparate sites. In contrast to coupons exposed only on one side, boldly exposed double-sided coupons corroded severely within 3 years. The effects on corrosion behaviour between individual coupons exposed at different heights and vertical continuous single strips of steel are described. Also reported are corrosion losses for continuous strips and for a series of coupons oriented in different directions. Observations of variability in corrosion losses for nominally identically exposed steel coupons are reported. The effect on corrosion losses with continued exposure to 5 years is reported and compared with information available in the literature.

Corrosion and Materials Degradation doi: 10.3390/cmd6030043

Authors: Clarissa Glawe Michael Raupach

With the increasing number of existing buildings, the implementation of durability-preserving repair procedures is becoming increasingly important. The chemical re-alkalization (CRA) enables the protection of reinforced concrete structures exposed to carbonation by maintaining or restoring the alkalinity in the concrete through the application of an alkaline mortar, such as hybrid alkali-activated binders (HAABs). However, the process of CRA is still insufficiently understood, which means that the requirements for the repair mortars can only be roughly formulated. This paper therefore investigates the process of CRA using laser-induced breakdown spectroscopy (LIBS). Based on the quantitative results of potassium transport in the composite system, a time-dependent attenuation factor can be determined that allows for the adaptation of Fick’s second law of diffusion previously used to predict CRA. The attenuation factor provides further insight into the course of potassium transport, which, based on the results, never follows an ideal diffusion process. Adjusting the diffusion law allows for an improved prediction of the maximum achievable re-alkalization depth depending on the repair mortar, where a potassium content of, e.g., 2.3 wt% leads to a complete re-alkalization of 16 mm. The present study demonstrates the potential of LIBS to quantitatively represent CRA for the first time thus providing new insights into potassium transport and the dynamics of the process.

Corrosion and Materials Degradation doi: 10.3390/cmd6030042

Authors: Nikolina Lešić Janez Kovač Ingrid Milošev

Polymer-bonded Nd–Fe–B and Sm–Fe–N magnets have excellent magnetic properties, but their corrosion resistance is inferior. Polymer-bonded magnets, the binary alloys Nd–Fe and Sm–Fe, and the metals Fe, Nd, and Sm were investigated in electrolytes with a pH range of 1.8 to 12.8. Potentiodynamic polarisation measurements showed that these materials corrode in acidic (H2SO4) and near-neutral (Na2SO4 and NaCl) electrolytes. Iron passivates at pH > 9, but Nd and Sm passivate only in strongly alkaline electrolytes (pH > 12). The alloys and magnets combine the characteristics of the individual metals. Scanning electron microscopy with energy-dispersive X-ray spectroscopy characterised the surface layers before and after electrochemical measurements. The speciation and the depth distribution of elements in the surface layers were analysed using X-ray photoelectron spectroscopy. In the H2SO4, a non-protective layer was formed. In NaCl, the corrosion products were more abundant, consisting of a mixture of oxides, hydroxides, and chlorides, while in NaOH, an oxide/hydroxide layer was formed. The corrosion product layers formed in the H2SO4 and NaCl electrolytes were significantly thicker for the Sm–Fe–N magnet than for the Nd–Fe–B magnet. Understanding the differences and similarities in the electrochemical behaviour of magnets in various electrolytes is essential to overcoming corrosion-related problems.

Corrosion and Materials Degradation doi: 10.3390/cmd6030041

Authors: Robert E. Melchers Igor A. Chaves

Chlorides have long been held responsible for the initiation and progression of the corrosion of reinforcing steels in concrete structures, with higher concentrations assumed to cause earlier and more severe subsequent reinforcement corrosion. However, extensive field observations and detailed experimental results show that, in well-compacted, low-permeability concretes, reinforcement corrosion often does not occur even in the presence of high concentrations of chlorides. If corrosion does occur, it has been observed as pitting (and crevice) corrosion primarily at air voids in the concrete at the steel–concrete interface. Herein, it is shown that this is consistent with thermodynamic principles (Pourbaix) for the pitting of steel in practical concretes with high pH and air voids, irrespective of chloride concentration. Any subsequent corrosion becomes inhibited, in part through the formation of corrosion products. The experimental observations also show that there is a separate, concurrent process of the dissolution of calcium hydroxide and its leaching from the concrete. The rate of dissolution is accelerated proportionally to the concentration of chlorides. This is the primary mechanism for longer-term reinforcement corrosion, eventually producing circum-neutral pH at the steel and thereby setting up the thermodynamics permitting general corrosion. The findings question the relevance of a critical chloride concentration as an indicator of the commencement of reinforcement corrosion. Concrete permeability, remaining alkali reserves (or pH), and physical observation of evidence of rust damage are better indicators.

Corrosion and Materials Degradation doi: 10.3390/cmd6030040

Authors: Willian Aperador Jonnathan Aperador J. C. Caicedo

This study investigates the effectiveness of calcined magnesium–aluminium layered double hydroxide (CLDH) as a functional additive for mitigating carbonation-induced corrosion in alkali-activated slag concrete (AASC). Mixtures incorporating different CLDH contents (0%, 2%, 4%, 6%, and 8%) were evaluated under accelerated CO2 exposure (3%, 65% RH, 25 °C) for 90 days. Mechanical characterisation was carried out through 28-day compressive strength tests to assess the potential impact of CLDH on the structural performance of the material. Performance characterisation included electrochemical impedance spectroscopy (EIS) to assess the corrosion of embedded steel, phenolphthalein spraying to determine the carbonation depth, and complementary techniques such as X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM/EDX) for assessments of the microstructural evolution. The results demonstrate that CLDH significantly enhances resistance to CO2 ingress, increasing the polarisation resistance (Rp) to over 55 kΩ·cm2 (at 6% CLDH) and reducing the carbonation depth by more than 50% compared to the reference mix. These improvements are attributed to the memory effect-induced regeneration of LDH-type lamellar phases, controlled release of OH− and CO32− anions, and progressive densification of the microstructure, thereby limiting the ingress of aggressive agents. The optimal dosage was identified as 6%, as higher contents offered no further improvement and evidenced the formation of residual phases such as MgO. This work highlights the potential of CLDH as an effective and sustainable strategy to enhance the durability of alkali-activated cementitious materials against degradation processes driven by carbonation and corrosion.

Corrosion and Materials Degradation doi: 10.3390/cmd6030039

Authors: Marshall Shuai Yang Chengqian Xian Jian Chen Yolanda Susanne Hedberg James Joseph Noël

This research investigates the impact of incorporating montmorillonite-based nanoclay additives on the anti-corrosive properties of a polyester/triglycidyl isocyanurate (polyester/TGIC) powder coating on phosphated steel. The self-repairing capability facilitated by the swelling and expansion of nanoclay was demonstrated to enhance the corrosion resistance of the coatings significantly. A statistical Mixture Design methodology was employed to establish the optimal combination of nanoclay dosage and coating film thickness. Nineteen experiments were conducted using Design of Experiments, and two regression models were developed using the measured polarization resistance (Rp) and specular gloss values as responses. The mathematical maximization of the Rp value predicted an optimal nanoclay dosage of 4.1% with a corresponding film thickness of 80 µm. Statistical and experimental verification validated the results obtained from the regression models. Notably, the optimized coating demonstrated an Rp value one order of magnitude higher than the coating with 4% nanoclay and a standard film thickness of 60 µm. The behavior of the newly developed coatings was analyzed and compared through measurements of open circuit potential, polarization resistance, and electrochemical impedance spectroscopy. The findings confirm the substantial improvement in the anti-corrosive and self-repairing properties of the polyester/TGIC powder coating with the incorporation of montmorillonite-based nanoclay additives.

Corrosion and Materials Degradation doi: 10.3390/cmd6030038

Authors: Tomáš Prošek Patrick Keil Kateryna Popova

Corrosion has a significant impact on the economic and environmental sustainability of metal-based infrastructure and products. This position paper explores the intrinsic relationship between corrosion protection and sustainability, examining the economic costs, environmental impacts and technological strategies involved. While corrosion results in resource waste, energy loss, and increased CO2 emissions, effective corrosion management can extend the service life of metallic components, thus preserving resources and minimizing environmental burden. The approaches such as Total Cost of Ownership (TCO) and Life Cycle Analysis (LCA) can provide a framework for selecting the most cost-efficient and environmentally friendly corrosion protection method in view of the required lifetime. The paper emphasises the crucial role of material selection, design optimization, recyclability and environmentally friendly coatings. Regulatory pressures and new trends such as machine learning are also discussed. Achieving sustainability goals requires greater awareness, education, interdisciplinary collaboration, and continued innovation in corrosion protection strategies.

Corrosion and Materials Degradation doi: 10.3390/cmd6030037

Authors: Dongfeng He

Corrosion of steel reinforcement is one of the primary causes of deterioration in reinforced concrete structures, significantly impacting their durability and structural performance. This review comprehensively examines various techniques used to evaluate rebar corrosion, categorizing them into electrochemical, physical, and advanced non-destructive methods. Each method is discussed with respect to its operational principles, advantages, limitations, and field applicability. This comparative overview aims to support the selection of suitable evaluation strategies tailored to diverse structural conditions.

Corrosion and Materials Degradation doi: 10.3390/cmd6030036

Authors: Ivan Netšipailo Lauri Aarik Jekaterina Kozlova Aivar Tarre Maido Merisalu Kaisa Aab Hugo Mändar Peeter Ritslaid Väino Sammelselg

We investigated the protective properties of ultrathin laminated coatings, comprising three pairs of Al2O3 and TiO2 sublayers with coating thicknesses < 150 nm, deposited on AISI 310 stainless steel (SS) and Si (100) substrates at 80–500 °C by atomic layer deposition. The coatings were chemically etched and subjected to corrosion, ultrasound, and thermal shock tests. The coating etching resistance efficiency (Re) was determined by measuring via XRF the change in the coating sublayer mass thickness after etching in hot 80% H2SO4. The maximum Re values of ≥98% for both alumina and titania sublayers were obtained for the laminates deposited at 250–400 °C on both substrates. In these coatings, the titania sublayers were crystalline. The lowest Re values of 15% and 50% for the alumina and titania sublayers, respectively, were measured for laminate grown at 80 °C on silicon. The coatings deposited at 160–200 °C demonstrated a delay in the increase of Re values, attributed to the changes in the titania sublayers before full crystallization. Coatings grown at higher temperatures were also more resistant to ultrasound and liquid nitrogen treatments. In contrast, coatings deposited at 125 °C on SS had better corrosion protection, as demonstrated via electrochemical impedance spectroscopy and a standard immersion test in FeCl3 solution.

Corrosion and Materials Degradation doi: 10.3390/cmd6030035

Authors: Elizaveta P. Simonenko Aleksey V. Chaplygin Nikolay P. Simonenko Ilya V. Lukomskii Semen S. Galkin Anton S. Lysenkov Ilya A. Nagornov Artem S. Mokrushin Tatiana L. Simonenko Anatoly F. Kolesnikov Nikolay T. Kuznetsov

Ultrahigh-temperature ceramic composites based on hafnium diboride have a wide range of applications, including as components for high-speed aircraft and energy generation and storage devices. Consequently, developing methodologies for their fabrication and studying their properties are of paramount importance, in particular in using them as an electrode material for energy storage devices with increased oxidation resistance. This study investigates the behavior of ceramic composites based on the HfB2-HfO2-SiC system, obtained using 15 vol% Ti2AlC MAX-phase as a sintering component, under the influence of subsonic flow of dissociated air. It was determined that incorporating the modifying component (Ti2AlC) altered the composition of the silicate melt formed on the surface during ceramic oxidation. This modification led to the observation of a protective antioxidant function. Consequently, liquation was observed in the silicate melt layer, resulting in the formation of spherical phase inhomogeneities in its volume with increased content of titanium, aluminum, and hafnium. It is hypothesized that the increase in the high-temperature viscosity of this melt prevents it from being carried away in the form of drops, even at a surface temperature of ~1900–2000 °C. Despite the established temperature, there is no sharp increase in its values above 2400–2500 °C. This is due to the evaporation of silicate melt from the surface. In addition, the electrochemical behavior of the obtained material in a liquid electrolyte medium (KOH, 3 mol/L) was examined, and it was shown that according to the value of electrical conductivity and specific capacitance, it is a promising electrode material for supercapacitors.

Corrosion and Materials Degradation doi: 10.3390/cmd6030034

Authors: Mattia Cabrioli María Silva Colmenero Matteo Vanazzi Luisa E. Mondora Gianluca Acquistapace Fabio Esposito Michela Giovanardi

In the framework of hydrogen production and storage for clean energy generation, the resistance to hydrogen embrittlement of a newly developed austenitic stainless steel is presented. Gas-atomized metal powders prepared from secondary-sourced metals were employed to manufacture test specimens with Laser Powder Bed Fusion (LPBF) technology. After machining and exposure to a controlled, pressurized hydrogen atmosphere at high temperature, the effect of hydrogen charging on the mechanical performance under static and dynamic conditions was investigated. The stabilizing effect of the optimized chemical composition is reflected in the absence of degradation effects on Yield Stress (YS), Ultimate Tensile Stress (UTS), and fatigue life observed for specimens exposed to hydrogen. Moreover, despite a moderate reduction in the elongation at fracture observed by increasing the hydrogen charging time, ductility loss calculated as Relative Reduction of Area (RRA) remains substantially unaffected by the duration of exposure to hydrogen and demonstrates that the austenitic steel is capable of resisting hydrogen embrittlement (HE).

Corrosion and Materials Degradation doi: 10.3390/cmd6030033

Authors: Dan Liu Xuan Xie Xuecheng Chen Rudolf Holze

Graphene, graphene oxide, reduced graphene oxide, and few-layer graphene as functional coating materials for corrosion protection in devices for electrochemical energy conversion and storage are reviewed. Reported applications are briefly described, enabling the reader to make an informed decision about the protective options based on the reported achievements.

Corrosion and Materials Degradation doi: 10.3390/cmd6030032

Authors: Govindarajan Narayanan Andrej Golowin

Corrosion, combined with cyclic loading, is inevitable and becomes a challenging problem, even when inherently corrosion-protected materials have been selected and applied based on established in-house experience. Aero engine mount structures are exposed to dusty and salty environmental conditions during both operational and non-operational periods. It is becoming tough to predict the remaining useful corrosion fatigue life due to the unascertainable material strength degradations under service conditions. As such, a rationalized approach is currently being used to assess their structural integrity, which produces more wastages of the flying parts. This paper presents a novel approach for predicting corrosion fatigue by proposing a random-parameter model in combination with validated experimental data. The two-random-parameter model is employed here with the probability method to determine the time-independent corrosion fatigue life of a magnesium structural casting, which is used heavily in engine front-mount aircraft systems. This is also correlated with experimental data from the literature, validating the proposed stochastic corrosion fatigue model that addresses the technical variances that occur during service to increase optimal mount structure usage using an automated data system.

Corrosion and Materials Degradation doi: 10.3390/cmd6030031

Authors: João Gabriel da Cruz Passos Luis Fernando Pedrosa Rabelo Carlos Alberto Della Rovere Artur Mariano de Sousa Malafaia

Measuring interfacial roughness is essential in evaluating the adhesion of coatings and thermally grown oxides. Conventional contact methods are often impractical for such analyses, especially when the interface lies beneath a nonremovable layer. This study proposes a semi-automated method combining an ImageJ macro and an R-language script to assess interfacial roughness from images obtained through scanning electron microscopy (SEM), leveraging chemical contrast between substrate and oxide. The approach preserves user input where interpretation is critical while standardizing measurement to reduce variability. Applied to 21 images from seven experimental conditions, the algorithm successfully reproduced the roughness ranking obtained from manual measurement while also significantly reducing measurement dispersion. Though it underestimates absolute roughness values compared with the user measurements (which should also happen with conventional contact methods), it offers a robust, flexible, and reproducible alternative for interface characterization.

Corrosion and Materials Degradation doi: 10.3390/cmd6030030

Authors: Johannes Wild Stefan Wagner Astrid Pundt Stefan Guth

Hydrogen embrittlement (HE) can significantly degrade the mechanical properties of steels. This phenomenon is particularly relevant for high-strength steels where large elastic stresses lead to detrimental localized concentrations of hydrogen at defects. In this study, unnotched rotating bending specimens of the bearing steel SAE 52100 (100Cr6) quenched and tempered at 180 °C and 400 °C were electrochemically charged with hydrogen. Charged and non-charged specimens then underwent rotating bending fatigue testing, either immediately after charging or after aging at room temperature up to 72 h. The hydrogen-charged specimens annealed at 180 °C showed a sizeable drop in fatigue limit and fatigue lifetime compared to the non-charged specimens with cracks mainly originating from near-surface non-metallic inclusions. In comparison, the specimens annealed at 400 °C exhibited a moderate drop in fatigue limit and lifetime due to hydrogen charging with cracks originating mostly from the surface. Aging had only insignificant effects on the fatigue lifetime. Notably, annealing of charged samples for 2 h at 180 °C restored their lifetime to that of non-charged specimens.

Corrosion and Materials Degradation doi: 10.3390/cmd6030029

Authors: Tumelo Hope Baloyi Motsie Elija Mashuga Abdelilah El-Khlifi Mohammad Salman Indra Bahadur

In a recent investigation the corrosion-fighting potential of five benzaldehyde derivatives were explored: 4-Formylbenzonitrile (BA1), 4-Nitrobenzaldehyde (BA2), 2-Hydroxy-5-methoxy-3-nitrobenzaldehyde (BA3), 3,5-Bis(trifluoromethyl)benzaldehyde (BA4), and 4-Fluorobenzaldehyde (BA5). Benzaldehyde derivative (BA-2) showed a maximum inhibition efficiency of 93.3% at 500 ppm. Several techniques were used to evaluate these compounds’ ability to protect mild steel from corrosion in a 1 M HCl solution, including potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), adsorption isotherms, and computational methods. Supporting techniques Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV-Vis) spectroscopy were also employed to validate the results. Despite sharing a common benzene ring, the molecules differ in their substituents, allowing for a comprehensive examination of the substituents’ impact on corrosion inhibition. PDP analysis disclosed that the inhibitors exhibited mixed-type inhibition behavior, interacting with anodic as well as cathodic reactions, influencing the corrosion process. EIS analysis revealed that benzaldehyde derivatives formed a protective passive film on the metal, exhibiting high corrosion resistance by shielding the alloy from corrosive attacks. The benzaldehyde inhibitors followed the Langmuir adsorption isotherm, with high R² values near one, indicating a monolayer adsorption mechanism. DFT results indicate that BA 2 is the most effective inhibitor. FTIR and UV-vis spectroscopy revealed the molecular interactions between metal and benzaldehyde derivative molecules, providing insight into the binding mechanism. Experimental results support the outcomes obtained from the molecular dynamic (MD) simulations.

Corrosion and Materials Degradation doi: 10.3390/cmd6030028

Authors: Emmanuel Sey Zoheir N. Farhat Ali Nasiri

This study investigates the tensile behaviors of wrought 44W steel, Monel 400, 304L austenitic stainless steel, and arc-directed energy deposited (arc-DED) 308L austenitic stainless steel under simulated hydrogen environments to evaluate their endurance to hydrogen embrittlement (HE). The specimens were subjected to cathodic hydrogen charging in an alkaline solution, followed by uniaxial tensile testing at a strain rate of 0.2 min−1. Based on measurements of elongation and toughness, the resistance to HE was ranked as follows: 304L stainless steel > Monel 400 > arc-DED 308L stainless steel > 44W steel. Notably, no significant changes were observed in the yield strengths, ultimate tensile strengths, or elastic modulus of 304L austenitic stainless steel, Monel 400, and 44W steel across all the levels of hydrogenation. However, the arc-DED 308L stainless steel exhibited a slight increase in these properties, attributed to its unique microstructural characteristics and strengthening mechanisms inherent to additive manufacturing processes. These outcomes contribute to a better understanding of the mechanical performance and suitability of these structural alloys in hydrogen-rich environments, highlighting the superior HE resistance of 304L stainless steel and Monel 400 for such applications.

Corrosion and Materials Degradation doi: 10.3390/cmd6030027

Authors: Marvin Schobel Christian Ekberg Teodora Retegan Vollmer Fredrik Wennerlund Svante Hedström Anders Puranen

The decommissioning and dismantling of nuclear research reactors can lead to a large amount of low- and intermediate-level radioactive waste. For repositories, the materials must be kept confined and safety must be ensured for extended time spans. Waste is encapsulated in concrete, which leads to alkaline conditions with pH values of 12 and higher. This can be advantageous for some radionuclides due to their precipitation at high pH. For other materials, such as reactive metals, however, it can be disadvantageous because it might foster their corrosion. The Studsvik R2 research reactor contained an AlMg3.5 alloy with a composition close to that of commercial Al5154 for its core internals and the reactor tank. Aluminum corrosion is known to start rapidly due to the formation of an oxidation layer, which later functions as natural protection for the surface. The corrosion can lead to pressure build-up through the accompanied production of hydrogen gas. This can lead to cracks in the concrete, which can be pathways for radioactive nuclides to migrate and must therefore be prevented. In this study, unirradiated rod-shaped samples were cut from the same material as the original reactor tank manufacture. They were embedded in concrete with elevated water–cement ratios of 0.7 compared to regular commercial concrete (ca. 0.45) to ensure water availability throughout all of the experiments. The sample containers were stored in pressure vessels with attached high-definition pressure gauges to read the hydrogen-induced pressure build-up. A second set of samples were exposed in simplified artificial cement–water to study similarities in corrosion characteristics between concrete and cement–water. Additionally, the samples were exposed to concrete and cement–water in free-standing sample containers for deconstructive examinations. In concrete, the corrosion rates started extremely high, with values of more than 10,000 µm/y, and slowed down to less than 500 µm/y after 2000 h, which resulted in visible channels inside the concrete. In the cement–water, the samples showed similar behavior after early fluctuations, most likely caused by the surface coverage of hydrogen bubbles. These trends were further supported by mass loss evaluations.

Corrosion and Materials Degradation doi: 10.3390/cmd6020026

Authors: Yuhan Su Emadoddin Majdabadi Farahani Qindan Huang Qixin Zhou

This study investigated the effects of alternating current (AC) interference on pipeline steel under cathodic protection (CP). In a simulated solution, real-time electrochemical measurements and corrosion rate analysis were conducted on two steel types (C1018 and X60) under various levels of AC interference with CP. Due to the complexity of AC-induced corrosion, relying on the shift in DC potential alone cannot accurately demonstrate the corrosion behavior in the presence of AC interference. In fact, such an approach may mislead the predictions of corrosion performance. It is observed that AC interference reduced the effectiveness of CP and increased the corrosion rate of the steel, both in weight loss and Tafel Extrapolation (Tafel) measurements. The study concluded that conventional CP standards used in the field were inadequate in the presence of high AC-level interference. Furthermore, this study found that a more negative CP current density (−0.75 A/m2) could reduce the effect of AC interference by 46–93%. This is particularly shown in the case of low-level AC interference, where the reduction can reach up to 93%. Utilizing the experimental data obtained by the two measurement methods, probabilistic models to predict the corrosion rate were developed with consideration of the uncertainty in the measurements. The sensitivity analysis showed how AC interference impacts the corrosion rate for a given CP level.

Corrosion and Materials Degradation doi: 10.3390/cmd6020025

Authors: Laurent Gaillet Alan Rondineau Sébastien Langlois Marc Demers Lamine Dieng

Aluminum Conductors Steel-Reinforced (ACSR) conductors are typically used in overhead transmission lines. Corrosion is an important degradation mechanisms that might affect the lifetime of this essential electricity network component. Considering the complexity of conductors, it is difficult to predict the damage of these conductors in corrosive environments. The objective of this paper is to evaluate the effect of grease and conductor geometry on the mechanical properties of aluminum strand composing the envelope of ASCR conductors. Thus, ACSR wires and strands have been evaluated in corrosion by the mean of accelerated corrosion tests. Tensile, fatigue and torsion test results are presented to examine the effect of corrosion on aluminum strands. The influence of corrosion on mechanical characteristics is established by a decrease in ductility, maximum elongation and tensile strength for the longest exposition (336 days). This significant reduction in the internal layer of ungreased wires confirms the importance of the galvanic corrosion mechanism of aluminum wires. This evolution concerns only aluminum wires of non-greased conductors, confirming the crucial role of grease as protection against corrosion.

Corrosion and Materials Degradation doi: 10.3390/cmd6020024

Authors: Jin-Yang Gui Zhao-Hui Lu Chun-Qing Li

Bond behavior between steel bars and concrete is fundamental to the structural integrity and durability of reinforced concrete. However, corrosion-induced deterioration severely impairs bond performance, highlighting the need for advanced and reliable assessment methods. This paper pioneers an algorithm for an advanced ensemble learning framework to predict bond strength between corroded steel bars and concrete. In this framework, a novel Stacked Boosted Bond Model (SBBM) is developed, in which a Fusion-Based Feature Selection (FBFS) strategy is integrated to optimize input variables, and SHapley Additive exPlanations (SHAP) are employed to enhance interpretability. A merit of the framework is that it can effectively identify critical factors such as crack width, transverse confinement, and corrosion level, which have often been neglected by traditional models. The proposed SBBM achieves superior predictive performance, with a coefficient of determination (R2) of 0.94 and a mean absolute error (MAE) of 1.33 MPa. Compared to traditional machine learning and analytical models, it demonstrates enhanced accuracy, generalization, and interpretability. This paper provides a reliable and transparent tool for structural performance evaluation, service life prediction, and the design of strengthening measures for corroded reinforced concrete structures, contributing to safer and more durable concrete structures.

Corrosion and Materials Degradation doi: 10.3390/cmd6020023

Authors: Glenda Lara Lopes Vasconcelos Carolina Alves Freiria de Oliveira Ana Paula Macedo Viviane de Cássia Oliveira Patrícia Almeida Curylofo Carlos Alberto Della Rovere Rodrigo Galo Bruna S. H. Tonin Valéria Oliveira Pagnano

This study demonstrates that effervescent denture cleansers can influence the electrochemical behavior of cobalt–chromium (Co-Cr) alloys, with a particular focus on their corrosion resistance. The findings underscore the importance for dental professionals of selecting cleansers compatible with Co-Cr prostheses to minimize material degradation and enhance clinical durability. Corrosion resistance was evaluated using open-circuit potential (OCP), corrosion current density (icorr), and passivation current density (ipass). Surface morphology and elemental composition were analyzed through scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Forty specimens (n = 5 per group) were individually immersed in one of ten test solutions: distilled water (DW), artificial saliva (AS), and eight commercial denture cleansers—Polident 3 minutes™ (P3M), Steradent™ (St), Polident for Partials™ (PP), Efferdent™ (Ef), Corega Tabs™ (CT), NitrAdine™ (Ni), Fixodent™ (Fi), and Kukident™ (Ku). Each specimen was exposed a single solution to avoid cross-contamination. Results showed St, Ef, and Ku had higher OCP values than DW and Ni (p < 0.05), indicating better corrosion resistance. AS exhibited lower OCP values compared to St (p = 0.034), Ku (p = 0.023), and P3M (p = 0.050). DW had higher icorr than PP (p = 0.030), CT (p = 0.005), and P3M (p = 0.003). For ipass, DW had lower values than Ef (p = 0.025) and Ku (p = 0.016). SEM and EDS revealed no significant surface alterations. Understanding the underlying corrosion mechanisms in different solutions provides valuable insights into optimizing material performance and ensuring durability in clinical applications. The corrosion resistance of Co-Cr depends on the stability of the passive oxide layer, which can be degraded by chloride ions, reinforced by sulfate ions, and influenced by active ingredients in denture cleansers. Overall, the Co-Cr alloy demonstrated acceptable corrosion resistance, underscoring the importance of selecting suitable cleansers for prosthesis longevity.

Corrosion and Materials Degradation doi: 10.3390/cmd6020022

Authors: Arshad Yazdanpanah Valentina Zin Francesca Valentini Luca Pezzato Katya Brunelli

The increasing demand for lightweight, high-performance materials in marine and offshore engineering has driven the development of hybrid solutions combining metals and composites. This study investigates the stress corrosion cracking (SCC) and tribocorrosion behaviour of a novel hybrid wire consisting of a superaustenitic stainless steel (6Mo) outer shell and a carbon fibre-reinforced polymer (CFRP) core. Microstructural analysis, residual stress measurement, and corrosion testing were performed to assess the integrity of the welded structure under harsh conditions. The results revealed that residual stresses and interdendritic segregation in the weld zone significantly contribute to SCC susceptibility, while the 6Mo steel showed improved corrosion resistance over 316L under tribocorrosion conditions but was more sensitive to the sliding frequency. These findings provide critical insights into the degradation mechanisms of metal composite hybrid wires and support the future design of corrosion-resistant components for offshore and structural applications.

Corrosion and Materials Degradation doi: 10.3390/cmd6020021

Authors: Frank Papworth Carmen Andrade Federica Lollini

In 2022, a working party (fib TG 8.9.3) was formed to try and better develop critical chloride (Ccrit) distributions for use in modelling new structures and assessing existing structures. The authors of this paper are leading TG 8.9.3. and are in the process of writing a Bulletin (the Bulletin) that will detail how Ccrit values have been developed since the 1970s. The Bulletin notes that chloride-induced corrosion initiation modelling based on Ccrit is not intended as a sole durability assessment tool for structures exposed to chloride. It is recognized that voids and moisture at the bar can control corrosion activation virtually independent of chloride content, but in most cases sufficient voids and moisture are present so that the arrival of adequate chloride triggers corrosion activation of the reinforcement. So, durability verification by modelling restriction of chloride penetration, so that the concentration at the bar is less than that commonly found to cause corrosion, seems appropriate. This empirical approach was first fully detailed in fib Bulletin 34 A key part in the empirical model is the ‘adequate chloride to trigger corrosion activation’ Ccrit. Although Ccrit has a wide distribution and has different distributions in different environments and concrete compositions, its use in modelling provides greater design flexibility and improved confidence compared to the Deemed-to-Satisfy (DtS) rules included in most codes. Because of the limitations in DtS provisions, modelling provides more effective designs by incorporating specific criteria for a broad range of exposures, materials, and construction methods. This paper proposes that a lower bound for Ccrit distributions for a range of materials and exposures can be developed from published papers. This paper includes Ccrit distributions for steel fibres, carbon steel (above and below water), high tensile steel, galvanized steel, and stainless steels. These are expected to be recommended in the Bulletin.

Corrosion and Materials Degradation doi: 10.3390/cmd6020020

Authors: Naroa Iglesias Esperanza Díaz

This study analyzes the effects of varying H2S and CO2 concentrations and temperature on the pH of geothermal fluids flowing through superduplex S32750 stainless-steel pipelines, classified as corrosion-resistant alloys (CRAs). Corrosive decay is evaluated by comparing OLI Studio software simulations with experimental data from the literature. The results indicate that an increase in the partial pressure of either gas lowers pH levels, with temperature exerting a more pronounced exponential effect on corrosion than gas partial pressure. When both gases are present, the dominant gas dictates the corrosion behavior. In cases where CO2 and H2S are in equal proportions, FeS2 forms as the primary corrosive product due to the higher potential corrosivity of H2S. The H2S/CO2 ratio influences the formation of passive films containing chromium oxides or hydroxides (Cr2O3, Cr(OH)3), iron oxides (Fe2O3, Fe3O4), or iron sulfides (FeS).

Corrosion and Materials Degradation doi: 10.3390/cmd6020019

Authors: Bayarmaa Tserendejid Erdenebold Urtnasan Jei-Pil Wang

Li-ion battery recycling is growing with better tech and eco-awareness. Explosions are possible during battery recycling due to their residual voltage. Proper battery discharge is vital to successful recycling. The goal of this study was to investigate a new method for discharging cylindrical batteries, utilizing a saltwater solution and copper conductors and analyzing the impact of both direct and indirect contact between the copper and the battery. A key variable impacting the discharge process was inconsistent spacing between the battery and the copper conductor. In the gap, the saltwater, functioning as an electrolyte solution, created an electrical short circuit, thus causing faster discharge. Because the battery was not in contact with the copper conductor during the discharge process, corrosion of the battery cap and valve occurred, leading to the battery’s anode and cathode elements dissolving into the solution. However, a near-total voltage drop of 99% was observed in the battery, indicating that it was almost completely discharged. Upon making contact with the copper strip during its discharge cycle, the battery exhibited no signs of corrosion. This report details the battery discharge process, encompassing an analysis of the electrochemical reaction, schematic diagrams, and a chemical analysis of the discharge precipitate.

Corrosion and Materials Degradation doi: 10.3390/cmd6020018

Authors: Bilal Ayyub Karl Stambaugh

Corrosion in infrastructure creates high-risk scenarios, and mitigation strategies are expensive, with significant annual costs globally. This paper advances the discourse of corrosion monitoring and tracking in infrastructure, emphasizing the importance of data analytics, AI, and Digital Twins (DT) for managing the infrastructure lifecycle while reducing risk and costs associated with corrosion. The non-parametric analysis of corrosion data is demonstrated to provide insights into spatial and temporal variations, helping in predictive modeling and decision-making. Strategic sampling and analysis of corrosion data help in making evidence-based maintenance decisions, reducing costs, and improving safety. AI analytics enhances the functionality of corrosion databases and Digital Twins, enabling predictive analytics and real-time simulations for better decision-making. Recommendations are provided for the implementation of AI in engineering applications, including data quantity and training resources, but offer significant potential for improved corrosion management.

Corrosion and Materials Degradation doi: 10.3390/cmd6020017

Authors: Alexander Ilyushechkin Veronica Gray Riley Ingle Lachlan Carter Liezl Schoeman

Knowledge of alloy behavior under industry-relevant conditions is critical to hydrogen production and processing, yet it is currently limited. To understand more about the impact of hydrogen damage on stainless steel 316 under realistic in-service conditions, we conducted a forensic investigation of two reactors exposed to various hydrogen-processing conditions. We examined samples of reactor walls exposed to hydrogen-containing atmospheres for >100 and ~1000 h at elevated temperatures during hydrogen separation and ammonia cracking. The samples were characterized by tensile testing, stretch–bend testing, and three-point bending. A loss in ductility and strength was observed for the reactor wall material compared with both untreated materials and materials annealed in neutral atmospheres at the same temperatures used during reactor operation. The three-point bend testing, which was conducted on inner and outer pipe-surface material extracted via electrical discharge machining, showed larger changes in the flexural modulus of exposed reactors but increases in the elastic limit. Microstructural observations revealed that hydrogen may play a role in stress relaxation, possibly promoting normalization at lower-than-expected temperatures. We also observed that materials exposed to ammonia undertake more damage from nitriding than from hydrogen.

Corrosion and Materials Degradation doi: 10.3390/cmd6020016

Authors: Feng Wang Thomas M. Devine

Passive films that form on Alloy 600 and Alloy 690 during four hours in simulated Primary Water (PW) of Pressurized Water Nuclear Reactors (PWRs) at 320 °C were investigated by in situ surface-enhanced Raman spectroscopy (SERS). Similar tests conducted on unalloyed nickel, unalloyed chromium, and laboratory alloys of Ni-10Cr, Ni-20Cr, Ni-5Cr-8Fe, and Ni-10Cr-8Fe aided in assigning the peaks in the surface-enhanced Raman (SER) spectra of the passive films of Alloy 600 and Alloy 690. SERS indicates an inner layer (IL) of Cr2O3/CrOOH forms on both Alloy 600 and Alloy 690 and that Alloy 690’s IL was more protective against corrosion due to its greater resistance to ion transport. The outer layer (OL) of Alloy 600 consists of NiO and spinels, FeCr2O4—M(Cr,Fe)2O4. The OL of Alloy 690 contains no spinel. A comparison of SER spectra in 320 °C PWR PW to the spectra following cooling down to room temperature and after exposure to air indicates some differences between in situ films and ex situ films.

Corrosion and Materials Degradation doi: 10.3390/cmd6020015

Authors: Joel Andrew Hudson Henry E. Cardenas

Iron and iron-nickel alloy electrodeposits synthesized from sulfate-based electroplating baths were applied to a mild carbon steel substrate. Coated specimens were immersed in an oxygen-saturated, weak ammonium hydroxide solution (pH 9.5–10.0), and their corrosion performance was evaluated using electrochemical techniques. Galvanic and general corrosion behaviors were analyzed to assess the sacrificial protection provided by Fe and Fe-Ni coatings relative to uncoated steel. The influence of anode-to-cathode (A/C) surface area ratios (1:1, 10:1, and 100:1) on the occurrence of plating-induced surface cracks was also examined. Surface morphology and elemental composition of the deposits were characterized. Results of the study indicated that increasing the Ni2+/Fe2+ molar ratio of the electroplating bath from 0 to 0.167 led to (1) reduced surface porosity and cracking, (2) decreased galvanic corrosion rates between the electrodeposit and substrate, and (3) a progressive increase in the temperature dependence of the general corrosion rate between 20 °C and 60 °C. The development of Fe and Fe-Ni alloy electrodeposits as protective coatings is of particular interest in water-tube power boiler applications, where production of corrosion products must be controlled. Further research is needed to develop coatings that perform predictably under elevated pressures and temperatures typical of operating boiler environments.

Corrosion and Materials Degradation doi: 10.3390/cmd6020014

Authors: Scott Briggs Mehran Behazin Fraser King

Copper has been proposed as a container material for the disposal of used nuclear fuel in a number of countries worldwide. The container materials will be subject to various corrosion processes in a deep geological repository, including radiation-induced corrosion (RIC) resulting from the γ-irradiation of the near-field environment. A comprehensive model is being developed to predict the extent of RIC by coupling a radiolysis model to the interfacial electrochemical reactions on the container surface. An important component of the overall model is a radiolysis model to predict the time-dependent concentration of oxidizing and reducing radiolysis products. As a first step in the model development, various radiolysis models have been validated against experimental measurements of the concentrations of dissolved and gaseous radiolysis products. Experimental data are available for pure H2O- and Cl−-containing solutions, with and without a gas headspace. The results from these experiments have been compared with predictions from corresponding radiolysis models, including the effects of the partitioning of gaseous species (O2 and H2) at the gas–solution interface. Different reaction schemes for the Cl− radiolysis models are also compared. The validated radiolysis model will then be coupled with interfacial reactions on the copper surface and additional processes related to the presence of bentonite clay in Steps 2 and 3 of the overall model, respectively.

Corrosion and Materials Degradation doi: 10.3390/cmd6010013

Authors: Kevin Raheem Anthony Betts John Cassidy Bernard Ryan

The hydrolytic stability of thin poly(ethyl 2-cyanoacrylate), PECA, adhesive films on grit-blasted mild steel substrates was investigated using electrochemical impedance spectroscopy (EIS). Using this novel approach for such adhesive films, the effects of two additives, salicylic acid (SA) and phthalic anhydride (PA), were studied, specifically measuring their influence on polymer film/surface impedance and capacitance changes over a period of 14 days. Results indicate that SA decreased the polymer film hydrolytic stability rapidly, resulting in a substantial drop in impedance modulus from ~10 kΩcm2 to ~10 Ωcm2 at 100 Hz due to electrolyte ingress, whilst the PA-containing film modulus also diminished from ~4 MΩcm2 to ~1 kΩcm2 at 100 Hz. Furthermore, the capacitance values of the SA-containing films rose (up to ~100 µFcm−2), demonstrating the onset of a charge transfer (corrosion) process within the first 12 h exposure to a saline electrolyte. In contrast, the PA-containing film’s transition from a film-dominated capacitance (~0.01 µFcm−2) to a larger double-layer capacitance took (~1 µFcm−2) took several days and was accounted for by differences in the additive’s chemistry, demonstrating the ability of EIS to detect changes in both bulk film (e.g., moisture ingress and bond scission) and metal-film interfacial processes (e.g., onset of corrosion) in real time. Comparison was also made with a standard industry combined tensile test/hydrolytic accelerated ageing regime. Unlike, EIS this did not, however, give useful time-dependent information, although after 6 weeks a decrease in bond strength occurred in the order PA-containing film < PECA< SA-containing film in agreement with the EIS results, thus demonstrating the effectiveness of EIS for monitoring the degradation of such thin film adhesives.

Corrosion and Materials Degradation doi: 10.3390/cmd6010012

Authors: Zohaib Hassan Joanna Idaszek Kamil Kaszyca Rafał Zybała Marek Tkocz Dariusz Kuc Jarosław Mizera Anna Dobkowska

In this work, the microstructure and degradation properties of a novel metal matrix composite composed of Mg with the addition of 1 vol. % hydroxyapatite nanopowder (Mg + 1 vol % nHAp) were evaluated. The composites in the form of discs produced using spark plasma sintering (SPS) were subjected to plastic deformation using a modified extrusion technique with an oscillating die located at the end of the extruder (called KoBo), which enables deformation without the preheating of the initial billet. The microstructure was analyzed using optical and scanning electron microscopy (SEM) with subsequent electron backscattered diffraction (EBSD) measurements. The corrosion properties were evaluated based on electrochemical and immersion tests. To assess early biological performance, cytotoxicity tests were performed. The addition of nHAp did not significantly change the corrosion rate; however, the subsequent plastic deformation greatly decreased it. Interestingly, the sample after plastic deformation without the preheating of the initial billet was characterized by the highest cell viability. Overall, the addition of nHAp improved the biological assessment of the extruded composite; however, during plastic deformation, due to the refinement of loosely adherent nHAp and the formation of bimodally distributed grain sizes, a high number of microgalvanic couples were formed, resulting in worse corrosion performance.

Corrosion and Materials Degradation doi: 10.3390/cmd6010011

Authors: Yu Liu Yun Zhou

Coastal reinforced concrete (RC) bridge piers are often subjected to seawater splash and tidal action, leading to bottom corrosion of the steel reinforcement and thereby producing the corrosion–induced cracks of concrete. The increased risk of vehicle collisions to piers poses significant threats to bridge and traffic disruption, potentially causing severe pier damage or even bridge collapse. Many studies have investigated the dynamic responses of bridge piers to vehicle collisions, but no study of the effect of the corrosion degradation of piers on vehicle collision response and damage has been reported yet. This study numerically investigates the influence of bottom chloride-induced corrosion on the truck collision response and damage of coastal RC bridge piers by using LS-DYNA. The results reveal that localized damage occurs in the impact zone for both intact and corroded piers. For the corroded pier, punching shear failure becomes the dominant failure mode and the pier is more vulnerable to collapse at lower truck velocities. Corrosion degradation influences the dynamic response, increasing the lateral displacement of the pier while reducing the impact force, particularly during the engine and cargo impact stages of truck collisions. The impulses in 500 ms collision time show reductions of 1.1% and 4.3% for piers with 45-year and 90-year corrosion, respectively. Notably, the lateral displacement at the bottom corrosion zone shows no oscillations due to the punching shear failure.

Corrosion and Materials Degradation doi: 10.3390/cmd6010010

Authors: Nobuo Osawa

Etching methods of aluminum foils used in electrolytic capacitors are selected based on the operating voltages, with DC and AC etching typically used for the anode foils of high- and low-voltage capacitors, respectively. The initial pits continue to grow and eventually form tunnels or cubic pits by DC or AC etching, respectively. This paper describes the pit formation and growth process, focusing on the involvement of passive film inside the pit and facet dissolution. In particular, it is found that high-purity aluminum foil containing Ti promotes the formation of passive film (etch film) inside pits during the cathodic half cycle of AC etching, and Cu promotes facet dissolution. These behaviors significantly affect the surface area expansion by electrolytic etching. In addition, the effects of crystal orientation, surface defects associated with oxide film crystallization, and a trace element, Pb, as factors affecting the pit initiation sites will be discussed.

Corrosion and Materials Degradation doi: 10.3390/cmd6010009

Authors: Sergey V. Dorozhkin

Research on bone regeneration has always been an intense and challenging field of tissue engineering. Biodegradable metals represent a novel class of biomaterials combining superior mechanical qualities with a capacity to promote bone growth. Among them, magnesium (Mg) and its alloys have been proposed as innovative biomaterials for bone grafting therapy due to their non-toxic nature and comparable mechanical properties to bones. In addition, they are lightweight, biocompatible and biodegradable. They offer several advantages over other implant metals, including reduced stress-shielding effects and unnecessity for a second surgery to remove them. Unfortunately, their clinical application is limited due to the rapid degradation rates in rather aggressive physiological conditions. Therefore, the development of Mg-based implants possessing a controlled degradation in accordance with the kinetics of bone healing is necessary. On the other hand, protective yet biocompatible and biodegradable surface coatings have emerged as a useful strategy to fulfill the diverse clinical requirements, including effective corrosion resistance. Calcium orthophosphates (abbreviated as CaPO4) are excellent candidates for producing such coatings as they are well tolerated by living organisms. However, due to its high chemical reactivity and a low melting point, Mg-based grafts require specific parameters for successful CaPO4 deposition. This paper reviews currently available preparation methods of CaPO4 deposits on Mg and its alloys, aiming to build up a comprehensive knowledge framework of deposition techniques, processing parameters, performance measures in terms of corrosion resistance, adhesion strength and biocompatibility. The literature analysis shows that CaPO4 protective coatings increase the ability of magnesium-based metallic biomaterials to withstand corrosion and improve the biocompatibility of their surfaces in all cases.

Corrosion and Materials Degradation doi: 10.3390/cmd6010008

Authors: María Criado Elena Torres Jaime Hinojosa-Platero Alicia Pachón-Montaño

In most countries, low- and intermediate-level wastes (LILWs) are cemented in carbon steel drums for later disposal. The durability of waste packages is determined by the chemical environment generated by both cement-based engineered barrier systems and the aggressive species present in the waste. Decontamination sludges are challenging wastes that are currently not accepted for final disposal due to their acidic nature and high concentrations of organic species and complexants. Thus, it was proposed to use electrochemical measurements to study the corrosion of steel sheets, simulating drums embedded in new alkali-activated slag (AAS) formulations with surrogate decontamination liquids, and determine their viability for use as confining matrices in order to increase the service life of the drums. The carbon steel coupon embedded in the Portland cement reference (R-L) paste showed the best corrosion resistance, followed by that of steel embedded in sodium silicate-activated slag (BFS-S-L) paste. This behaviour may be related to an improvement in the protective nature of the surface film. However, in sodium carbonate-activated slag (BFS-C-L) paste, the effect of the sludge in the matrix seemed to be more intense, leading to a pH decrease in the paste porewater, an effect that could hinder the formation of a passive layer on the surface of the carbon steel. Under such conditions, the initiation of the corrosion process seems to be favoured, resulting in the formation of a non-protective scale consisting mainly of hematite.

Corrosion and Materials Degradation doi: 10.3390/cmd6010007

Authors: Luca Paterlini Andrea Marinelli Andrea Brenna Marco Ormellese

Carbon steel structures employed to convey hydrocarbons and other dangerous fluids, such as oil or flammable liquids, are equipped with degradation prevention systems, which typically consist of a cathodic protection (CP) system combined with an external insulating coating, both designed to reduce the corrosion rate below 10 µm/year. The presence of electrical interference, both AC and DC, can cause significant corrosion damage to metallic structures, even when CP is applied. DC interference is determined by the presence of a third-party CP system or public transportation system. AC interference may occur through conduction or induction mechanisms, caused by high-voltage powerlines or high-speed trains, powered by AC. Both interferences may lead to localized corrosion at coating defects, despite compliance with the −0.850 V saturated Cu/CuSO4 reference electrode (CSE) protection criterion. Considering AC-induced corrosion, both field failures and laboratory investigations have demonstrated that corrosion can occur at industrial frequencies, and when CP is applied following the standards. Even though AC-induced degradation is generally not as severe as DC interference, uncertainties remain regarding the protection potential range necessary to achieve acceptable corrosion prevention under AC interference. To formulate a CP criterion under AC interference, weight loss measurements were conducted on carbon steel samples under cathodic protection in solutions that simulate real soil conditions. Carbon steel coupons protected by CP were interfered with AC densities ranging from 1 A/m2 to 800 A/m2 for four months. During this time interval, polarization potential, protection current density and AC density were monitored. Based on the experimental data gathered during this study, a proposal for a risk map is also suggested. The results indicate that overprotection (potentials < −1.2 V CSE) represents the most dangerous scenario when AC interference is involved.

Corrosion and Materials Degradation doi: 10.3390/cmd6010006

Authors: Kazem Reza Kashyzadeh Waleed Khalid Mohammed Ridha Siamak Ghorbani

In the current study, the authors have listed the causes of common failures in hydro turbine blades. In the following, coatings, as one of the practical solutions that can be utilized in the hydropower industry, were selected for further investigation. In this regard, nanocoating technology is used to prevent the above-mentioned failures, as well as to extend the service lifetime of turbine blades, to increase the inspection time, i.e., the overhaul intervals, and to reduce repair costs. Therefore, firstly, the raw materials of runner blades in different types of turbines were checked. The collected data revealed that this equipment is usually made of stainless steel (i.e., 304 and 316L). Therefore, the main focus of the current research was a general investigation of the effects of different nanocoatings on the material properties, including the wear, corrosion, and erosion, of 304 and 316L steels. Finally, a coating process used in this industry that is suitable for overhaul rather than initial construction was investigated. The advantages of using nanocoatings compared to traditional coatings in this industry were enumerated. In addition, the effects of single-layer and multi-layer coatings with different compositions on the corrosion, wear, and erosion properties of each of these stainless steels were discussed. Eventually, considering the gaps in past research and summarizing the collected results, a future research direction was proposed, including different combinations of materials to create new nanocoatings (with different percentages of nano alumina and titanium carbide).

Corrosion and Materials Degradation doi: 10.3390/cmd6010005

Authors: Andreas G. Varias

Chemical Equilibrium Fracture Mechanics (CEFM) studies the effect of chemical reactions and phase transformations on crack-tip fields and material fracture toughness under chemical equilibrium. An important CEFM direction is hydrogen-induced embrittlement of alloys, due to several industrial applications, including those within the industrial value chain of hydrogen that is under development, which, according to European and international policies, are expected to contribute significantly to the replacement of fossil fuels by renewable energy sources. In the present study, the effect of hydrogen on the crack-tip fields of hydride- and non-hydride-forming alloys is examined. The crack-tip stress and hydrogen concentration distributions are derived under hydrogen chemical equilibrium, which is approached by considering the coupling of the operating physical mechanisms. In all cases, analytic relations are derived, thus facilitating integrity assessments, i.e., without the need to rely on complicated numerical methods, expected to lead to the development of respective tools in industrial applications. It is shown that, in the case of hydride precipitation, there are significant deviations from the K, HRR, and Prandtl fields, and, thus, the well-known approaches of Linear Elastic Fracture Mechanics (LEFM) and Elastic–Plastic Fracture Mechanics (EPFM) need to be accordingly modified/extended.

Corrosion and Materials Degradation doi: 10.3390/cmd6010004

Authors: Bruce G. Pound

Biomedical alloys in general, except for the biodegradable type, exhibit passive behavior in neutral chloride solutions. Two commonly used biomedical alloys are nitinol (NiTi) and Co-35Ni-20Cr-10Mo (CoNiCrMo). In this work, the passive behavior of electropolished NiTi and CoNiCrMo in a simulated physiological solution (phosphate-buffered saline) was compared using data largely obtained from our previous studies involving potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The potentiodynamic results showed a marked difference in passive behavior between the alloys, with NiTi remaining completely passive up to the oxidation of water and CoNiCrMo, in contrast, undergoing solid-state oxidation and then transpassive dissolution. Both alloys exhibited Tafel-type behavior over the initial part of the passive range. A small but distinct difference in the apparent Tafel slopes was found between the two alloys and can be attributed to the difference in their predominant oxide; that is, TiO2 versus Cr2O3. The EIS results also showed marked differences between the alloys in terms of the oxide thickness and resistivity. The thickness was greater for NiTi—consistent with surface analytical results—and differed in potential dependence between the two alloys in the passive region. The oxide resistivity, conversely, was substantially lower for NiTi and showed a similar potential dependence for the two alloys.

Corrosion and Materials Degradation doi: 10.3390/cmd6010003

Authors: Marcella Amaral Isaac Aguiar Oliveira Diogo Henrique de Bem Giovana Costa Réus Gustavo Macioski Marcelo Miranda Farias Marcelo Henrique Farias de Medeiros

Corrosion is one of the causes of failure in reinforced concrete structures, and forming a passive film on the steel is essential for protection. Although several studies have looked at passive film formation in concrete pore solutions, few have considered its formation in hardened concrete and the influence of silica fume (SF) in the binder composition. This study aims to evaluate the influence of the SF content on passive film formation time in concrete. Periodic measurements assessed the electrical resistivity and corrosion current density of concrete samples containing 5%, 10%, 15%, and 20% SF. The alkalinity of the mixtures and the kinetics of the pozzolanic reaction were also monitored by XRD and titration tests. The control mixtures exhibited susceptibility to corrosion, regardless of the curing age evaluated. In contrast, the partial replacement of cement with SF accelerated the formation of the passive film on the steel surface, suggesting a delayed onset of corrosion due to modifications in the physical properties of the concrete. Also, the portlandite content and pH can predict passive film formation, with SF significantly accelerating this process.

Corrosion and Materials Degradation doi: 10.3390/cmd6010002

Authors: Elke Ziehensack Kai Osterminski Christoph Gehlen

Corrosion investigations of steel-reinforced concrete structures are often based on half-cell potential measurements, in which the diffusion potentials can be a significant source of measurement errors. Therefore, the diffusion potentials must be taken into account in order to enable accurate half-cell potential measurements. This study covers the measurement of the diffusion potentials in cement mortars with pH differences due to carbonation and various mortar moisture conditions. The effect of chloride exposure of the mortars on the diffusion potentials is outside of the scope of this study. The mortars consisted of ordinary Portland cement (OPC) and blast furnace cement (BFC) with water–cement ratios of 0.5–0.7. The use of color indicators allows for the observation of the pH drop around the carbonation front, which propagates as the carbonation progresses. The diffusion potentials in the mortars under study have measurement values between 10 and 240 mV. The measured diffusion potentials seem to correlate with the magnitude of the pH drop rather than the progress of the carbonation depth. The moisture condition of the mortars significantly affects the magnitude of the arising diffusion potentials.

Corrosion and Materials Degradation doi: 10.3390/cmd6010001

Authors: Yanwen Liu Douglas Beaumont Xiaorong Zhou Timothy Burnett Suzanne Morsch Stuart Lyon Paul Iannarelli Claudio Di Lullo Niek Hijnen Reza Emad Lawrence Coghlan Teruo Hashimoto

Seawater ballast tanks in vessels are subject to severe service conditions caused by repeated filling/emptying, as well as temperature variation. Consequently, relatively thick, barrier-type coatings are used for corrosion protection of their internals. These are generally formulated with solvent-based epoxy binders and contain a range of flake pigments designed to limit environmental entry. Here, we report on a detailed study of damage processes in order to understand the mechanisms of failure after hygro-thermal cyclic corrosion testing. Similar formulations were cured using variant phenalkamine cross-linkers. Visual observation after corrosion testing shows minimal changes and no sign of corrosion damage. However, high-resolution analytical microscopy and nanoscale tomography reveal the onset of microstructural and chemical damage processes inside the coating. Thus, kaolin and talc pigments in the coating remained stable under hygro-thermal cycling; however, dolomite and barium sulphate dissolved slightly, causing voids. Galvanic protection of the substrate by aluminium flake pigments was disproven as no electrical connection was evident. Vibrational spectroscopy revealed a decrease in residual epoxy functionality after exposure for the coating cured with the more stable phenalkamine. This was correlated with an increase in glass transition temperature (Tg) and no observable corrosion of aluminium flakes. In contrast, the less stable phenalkamine cross-linker caused the binder Tg to decrease and aluminium flakes and substrate corrosion to become evident.

Corrosion and Materials Degradation doi: 10.3390/cmd5040031

Authors: Ladislav Vrsalović Senka Gudić Antonia Talijančić Jelena Jakić Jure Krolo Iman Danaee

Ti and Ti6Al4V alloy are extensively utilized in structural parts in engineering applications and the production of medical implants due to their excellent mechanical properties, lightweight, and high corrosion resistance. This study comprehensively evaluates their corrosion behavior in three challenging aquatic environments: brackish water, seawater, and seawater bittern. Utilizing open circuit potential (EOC) measurements with polarization techniques (linear and potentiodynamic) and electrochemical impedance spectroscopy (EIS) measurements, the research highlights distinct environmental influences on corrosion performance. Notably, Ti and Ti6Al4V alloy demonstrated exceptional stability with the highest polarization resistance and lowest corrosion current in brackish water, while seawater bittern presented the most demanding condition for Ti6Al4V. Additionally, the analysis of the electrode surfaces after polarization measurements using optical microscopy, optical profilometry, and SEM/EDS tests revealed minor damage, indicating the high corrosion resistance of these materials. This study advances the understanding of Ti and Ti6Al4V alloy performance in diverse environments and offers valuable insights for optimizing their use in harsh aquatic conditions, particularly for applications requiring durability and longevity.

Corrosion and Materials Degradation doi: 10.3390/cmd5040030

Authors: Carmen M. Abreu Iria Feijoo Gloria Pena M. Consuelo Pérez

The objective of this research is to enhance the mechanical and corrosion resistance properties of a cast Ni-Al bronze (NAB). To achieve this, the effect of deep cryogenic treatment (DCT), a process that has shown promise in other alloys, is initially investigated. It is demonstrated that, in the case of NAB, DCT induces only minor microstructural changes, which do not lead to any significant improvement in its properties. Consequently, it is proposed that a combined treatment be employed, involving annealing either before or after DCT. The results indicate that annealing at 675 °C for 2 h following cryogenic treatment at −180 °C increases the yield strength by approximately 11%. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in simulated seawater further confirm that this combination results in the formation of oxide layers with enhanced protective capacity. These improvements are attributed to the significant refinement and homogenization of the microstructure, including the globularization of the kI, kII, and, particularly, kIII phases, and an increase in the precipitation of the kIV phase in a finer and more homogeneous form within the alpha phase.

Corrosion and Materials Degradation doi: 10.3390/cmd5040029

Authors: Bruno D. F. Souza Mateus R. Lage Adenilson Oliveira dos Santos Francisco Ferreira de Sousa Rodrigo Gester Stanislav R. Stoyanov Tarciso Andrade-Filho

Ascorbic acid is widely used as an immunity-enhancing and antioxidant supplement for treating influenza and other virus-based illnesses. The lactone ring and the oxygenated groups make this system and derived structures attractive as possible environmentally friendly green corrosion inhibitors. Thus, we investigate the corrosion inhibition influence of ascorbic acid, ascorbate, and dehydroascorbic acid on the α-Fe(110) surface using density functional theory calculations. The adsorption, density of states, and charge transfer results indicate that dehydroascorbic acid is this series’s most potent corrosion inhibitor. The projected density of states near the Fermi energy reveals notable hybridization between the iron surface and dehydroascorbic acid adsorbed on it. The calculated structural, electronic, and energetic properties obtained in this work pave the way for understanding the corrosion inhibitory performance of the investigated systems.

Corrosion and Materials Degradation doi: 10.3390/cmd5040028

Authors: Lyna Amrouche Patrice Berthod

In order to discover how the multiple oxides observed in the final external scales after long exposure of a low-Mn, high-Cr Cantor’s alloy to hot air were formed, oxidation tests in a furnace were performed for seven different durations. Metallographic characterization was carried out concerning the oxidation products obtained after each test duration. The different oxides did not appear one after the other, but simultaneously, early on in the exposure to hot air and after. They all thickened progressively and the chemical composition of each also evolved with time, more or less. Globally, the innermost oxide is almost entirely chromia, much richer in Cr than in Mn, while the outermost one contains principally Mn. The interrupted tests also allowed specifying the mass gain kinetic, which is parabolic and twice as fast as a chromia-forming alloy. Despite the lowered content in Mn, manganese still plays an important role in the oxidation phenomenon, starting very early.

Corrosion and Materials Degradation doi: 10.3390/cmd5040027

Authors: Jessica Roscher Dan Liu Xuan Xie Rudolf Holze

Molecular aromatic corrosion inhibitors are frequently applied to slow down the corrosion of iron, its alloys and numerous other metallic materials. This case study with three representative aromatic inhibitors and a pure iron electrode aims at the verification of the reported conclusions regarding these inhibitors and at the verification and comparison of electrochemical corrosion assessment methods with attention to differences between iron alloys (steels) and pure iron possibly related to the presence/absence of alloying elements and non-iron impurities.

Corrosion and Materials Degradation doi: 10.3390/cmd5040026

Authors: Kateryna Popova Maria Fátima Montemor Tomáš Prošek

Highly sensitive resistometric sensors were applied for the real-time corrosion monitoring of carbon steel protected with a polyolefin coating with and without an inhibitor under static and dynamic atmospheric and immersion conditions. The results were compared with conventional electrochemical impedance spectroscopy (EIS) data. An increase in the coating thickness from 20 µm to 50 µm and an addition of 1wt.% tannic acid significantly improved the coating corrosion stability. Based on the real-time corrosion data, the drying stage of atmospheric exposure in a chloride-rich environment was found to be the most critical. The highest corrosion rate was detected at 50% relative humidity when the electrolyte corrosiveness in coating defects reached the maximum. Resistometric sensors have the potential to become an interesting alternative for evaluating coating performance and degradation mechanisms in both laboratory and industrial applications.

Corrosion and Materials Degradation doi: 10.3390/cmd5040025

Authors: Soheil Saedi Ahmed Korra Hatim Raji Hamdy Ibrahim

This study examines the effects of heat treatment on corrosion behavior of equiatomic AlCoCrNiFe high-entropy alloy within a solution treatment temperature range of 800–1100 °C. Experimental observations on phase formation were compared with thermodynamic predictions. The microstructure, mechanical properties, and aqueous corrosion behavior of the as-deposited alloy were analyzed and contrasted with heat-treated samples. The results showed a decline in the corrosion resistance of the AlCoCrNiFe after heat treatment, which was attributed to chemical segregation and Cr depletion in the microstructure matrix. Additionally, post-corrosion analysis revealed a reduced volume fraction of protective oxides in the heat-treated samples.