Search Results (1,011)

Developing lightweight materials that simultaneously achieve efficient electromagnetic wave absorption and robust corrosion resistance remains a significant challenge for marine stealth and electromagnetic protection applications. The main obstacle lies in the rational integration of electromagnetic attenuation capability, impedance matching, and corrosion protection. In this work, a multilayer carbon-structured BaTiO₃@C nanocomposite (CSTB-x) was successfully fabricated via freeze-drying combined with in situ pyrolysis. During the carbonization process, chitosan (CS) was transformed into a nitrogen-doped multilayer porous carbon framework, while BaTiO₃ particles were embedded into the carbon matrix to construct a BaTiO₃@C heterostructure. Benefiting from optimized impedance matching and the synergistic contributions of conduction loss, dipolar polarization, and interfacial polarization, CSTB-1.0 delivered a minimum reflection loss (RL_min) of −48.07 dB at 6.16 GHz with a thickness of 3.32 mm, and achieved a maximum effective absorption bandwidth (EAB) of 7.04 GHz at a thickness of 1.88 mm. In addition, CSTB-1.0 exhibited a low corrosion current density (8.93 × 10⁻⁶ A/cm²) and a high polarization resistance (7.87 × 10³ Ω∙cm²), indicating excellent corrosion protection performance. The enhanced corrosion resistance is mainly attributed to the barrier effect of the multilayer carbon framework and the tortuous diffusion pathways generated by the porous and core–shell structures. Moreover, the material showed a minimum radar cross-section (RCS) value of −41.25 dBsm, demonstrating remarkable electromagnetic scattering suppression capability. These results provide a feasible strategy for the design and fabrication of marine stealth materials with integrated microwave absorption and corrosion resistance. Full article

As one of the most promising new materials in the field of materials science, high-entropy alloys (HEAs) have attracted widespread attention due to the unique structure, exceptional properties and engineering performance, and complex composition. The CoCrFeNiZr_0.5 eutectic high-entropy alloys (EHEAs) exhibits excellent high-temperature thermal stability, ductility, creep resistance, and corrosion resistance, demonstrating great potential for applications in marine equipment. This paper explores the engineering feasibility of electrical discharge machining (EDM) of CoCrFeNiZr_0.5 EHEAs and investigates the EDM of micro-holes using a hollow copper electrode on a CNC EDM drilling machine under various machining parameters, including different gap voltage, pulse-on time, pulse-off time, and pulse amplifier settings. The effects of these parameters on the inlet diameter, outlet diameter, and recast layer of the micro holes are analyzed. The optimal micro-hole machining parameters are determined by comprehensively considering machining efficiency and electrode wear: gap voltage of 33 V, pulse-on time of 3 μs, pulse-off time of 1 μs, and pulse amplifier output of 3 A. Adopting the parameters to process a button ingot sample with a depth of 5 mm, it was found that the machining speed is 7.79 mm/min and the electrode wear is 1 cm. This research renders the foundation for further development and engineering application of CoCrFeNiZr_0.5 EHEAs in the context of high-value material design and manufacturing. Full article

Chloride-induced corrosion of steel reinforcements is one of the main factors restricting the durability of reinforced concrete structures. Chromium (Cr) alloying is an effective strategy to enhance the corrosion resistance of steel. However, the appropriate Cr content for different environments remains undetermined. In this study, steels with three different Cr contents of 0, 5, and 10 wt.% were prepared. Electrochemical methods and physical characterization techniques were used to investigate the effects of Cr content on the passive film and corrosion behavior of steels in a simulated concrete pore solution under chloride attack. The results show that Cr alloying increases the critical chloride concentration for steel depassivation, passive film resistance, and charge transfer resistance. Specifically, the critical chloride concentrations of 0Cr, 5Cr, and 10Cr are 0.63, 0.81, and 1.56 mol/L, respectively. In a simulated pore solution with 0.6 mol/L chloride, the charge transfer resistances of 0Cr, 5Cr, and 10Cr are 4.1, 5.8, and 63.4 × 10⁵ Ω·cm², respectively, corresponding to corrosion rates that are 1.39- and 15.31-times lower for 5Cr and 10Cr relative to 0Cr. Therefore, in concrete exposed to marine chloride attacks, the use of high Cr alloying is necessary. Although the cost increases and the weldability deteriorates, the improvement in corrosion resistance is far superior to that of medium Cr alloying. The excellent corrosion resistance of high-Cr steel stems from its passive film mainly composed of stable Cr₂O₃ with a lower oxygen vacancy defect density, while that of 5Cr is dominated by less stable Cr(OH)₃, which weakens the corrosion resistance of the passive film. Full article

This study investigated the anti-corrosion performance of multilayer polymeric coatings applied on 6005A and 6082 aluminum alloys under the influence of the monsoon tropical climate of Thailand. The coated samples, which represented the material used for the vehicle body of high-speed trains, were exposed to real atmospheric conditions of urban (Bangkok City) and marine (Songkhla City) environments. The maximum duration of the continuous exposure test was 18 months. After the exposure test, the physical deterioration characteristics of the coatings were examined with the aid of scanning electron microscopy (SEM) and a pull-off adhesion test. Electrochemical impedance spectroscopy (EIS) was performed in 3.5 wt% NaCl solution at 25 °C to evaluate the coatings’ anti-corrosion performance after various atmospheric exposure periods. Based on the EIS results, the low-frequency impedance of the exposed coatings remained above 10⁹ Ω·cm², indicating that the anti-corrosion coatings provided sufficient protection against atmospheric corrosion for the alloy. However, gradual degradation of the anti-corrosion coatings was observed, particularly in the marine-coastal environment. Quantitative estimation results suggested that the anti-corrosion coatings used in this study could provide service lives of approximately 8 and 11 years in marine-coastal and urban environments, respectively. Full article

The performance requirements of wear-resistant and anti-corrosion coatings for marine equipment continue to increase. Diamond-like carbon (DLC) film has become a preferred protective material due to its high hardness, low friction and chemical inertia. To reveal the tribocorrosion mechanism of Si-doped DLC films in a seawater environment, a Cr-WC-WC/C transition layer and DLC-Si films with different Si contents were prepared by high-power pulsed magnetron sputtering (HiPIMS) technology on 304 stainless steel. The tribocorrosion tests were carried out under open-circuit potential and dynamic polarization conditions in seawater. The results show that Si doping improved the tribocorrosion resistance of the films. The sample with Si content of 9.26 at.% has the lowest self-corrosion current density, the smallest volume loss, complete wear scar morphology and no obvious substrate exposure. The strengthening mechanism is attributed to Si doping, which induces the formation of a SiO_x passivation film and a hydrated silica gel lubrication layer. This establishes a synergistic solid-chemical lubrication system, inhibits sp² cluster growth, prolongs the diffusion path of corrosive media, and mitigates the damaging wear–corrosion synergy. This study confirms that moderate Si doping can significantly improve the wear resistance and corrosion resistance of DLC films in a seawater environment, and provides a theoretical basis for the design and application of carbon-based protective coatings for marine equipment. Full article

Marine biomucus, a complex biomolecular gel, plays a pivotal role in defense against biofouling, mitigation of environmental stress, and regulation of biomineralization. This study conducts a comparative analysis of the physicochemical properties of mucus secreted by three distinct tissues—labial palps, mantle, and gills—of the Pacific oyster (Crassostrea gigas), alongside their freeze-dried counterparts. By integrating amino acid profiling, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), we explored potential correlations between chemical composition, microstructure, and hypothesized macroscopic functional properties. Our findings inspire distinct tissue-specific structural characteristics that suggest potential structure–function relationships: The structure of labial palps mucus leads to the hypothesis that it may act as a viscous barrier-like property; mantle mucus shows features that could potentially support the formation of continuous films by a dense hydrogen-bond network; and gill mucus exhibits a porous three-dimensional network that potentially facilitates the process of respiratory and feeding. This work not only explores the material basis and potential structure–function relationships of C. gigas mucus as a natural biopolymer but also provides a potential theoretical framework for the design of novel marine-inspired biomimetic materials. Full article

Durable concrete has emerged as a key material strategy for enhancing the performance and extending the service life of infrastructure in chloride-containing environments, owing to its resistance to chloride ingress and corrosion-induced deterioration. This paper presents a systematic review of recent advances in durable concrete, establishing a comprehensive technical framework encompassing material design, transport mechanisms, and lifecycle durability management. Research demonstrates that supplementary cementitious materials, corrosion inhibitors, and non-metallic reinforcements significantly mitigate chloride penetration and corrosion while improving durability performance in various structures, including marine, coastal, and transportation infrastructures. The effectiveness of these approaches is fundamentally attributed to pore structure refinement, electrochemical regulation, and the elimination of corrosion-prone components. However, transitioning durability technologies from “effective” to “reliable and designable” still faces critical challenges: the mechanisms of multi-factor coupling under complex environments remain unclear, transport models under non-steady conditions require further development, and inconsistencies persist among international durability design codes. Accordingly, this paper highlights that future research should focus on developing multi-scale coupled models, refining environmental classification and prediction methods, integrating intelligent sensing technologies, and establishing unified lifecycle-based design frameworks. These advancements are essential to promote durable concrete from material-level optimization toward system-level, intelligent durability design, thereby supporting the development of sustainable infrastructure. Full article

The dynamics of calcium carbonate structures in marine organisms (skeletons and shells) has become increasingly important due to heightened interest in marine environmental acidification. Research into molluscan shell corrosion and calcification in response to acidification is typically carried out in laboratory-controlled settings, which often overlooks the intricate interactions found in natural environments. Mollusks inhabiting intertidal zones are especially susceptible to intense shell weathering caused by tidal cycles of heating, cooling, wetting, and drying, exacerbated by solar radiation during periods of air exposure. We investigated the effect of sun exposure (solar radiative heating) on both outer shell corrosion and inner shell compensatory calcification in the tropical oyster, Saccostrea scyphophilla. Shell properties were compared between oysters from neighboring populations in sun-exposed and shaded habitats. Habitat temperatures were measured using iButtons, and right shell valve corrosion was quantified. Compensatory calcification was assessed through measurements of shell thickness, shell density, shell compression strength, and mineralogical properties. Our results revealed that oysters in the sun that experience global irradiance, higher temperature peaks and broader daily temperature ranges (averaging an increase of 10 °C) show considerably greater outer shell surface corrosion (87%) compared to shaded oysters (31%) that experience only diffuse irradiance. Sun-exposed shells also become thickened in the midsection and around the adductor muscle, and they are slightly stronger, indicating compensation for the outer shell loss. These findings highlight the need for caution when interpreting molluscan shell dynamics based on laboratory marine acidification protocols that fail to account for the many natural environmental factors influencing shell formation and dissolution. Full article

This study investigates the hydrogen embrittlement susceptibility of laser melting deposition (LMD)-produced Ti-6Al-4V alloy with different build orientations (0°, 45°, 90°) through electrochemical hydrogen charging, slow strain rate testing, and microstructural characterization. Ti-6Al-4V alloys are widely used in marine and offshore engineering, where cathodic protection and corrosion reactions can generate hydrogen, leading to hydrogen ingress and potential embrittlement. Results show that prolonged hydrogen charging induces hydride formation, α-phase fragmentation, and β-phase dissolution, significantly degrading corrosion resistance and mechanical properties. Hydrogen embrittlement susceptibility exhibits notable anisotropy: elongation reductions for 0°, 45°, and 90° specimens are 40.1%, 40.8%, and 29.4%, respectively. The relatively superior resistance observed in the 90° orientation may be associated with its single-layer structure and more uniform dimple distribution. In contrast, the multilayer interfaces in other orientations are likely to serve as preferential sites for hydrogen accumulation, which may contribute to the increased embrittlement susceptibility. This research reveals the failure mechanism of LMD Ti-6Al-4V in hydrogen environments and supports its application in marine engineering. Full article

Island reef road construction faces a complex marine service environment characterized by high salinity and high humidity. Meanwhile, rapid construction and prompt subgrade repair are urgently required, creating a strong demand for novel calcareous-sand-based stabilization materials that combine excellent mechanical performance with resistance to seawater erosion. To this end, this study developed an early-strength cemented calcareous-sand reinforcement material for road base construction. Sulfoaluminate cement (SAC) and ferrite-aluminate cement (FAC), both featuring rapid setting/early strength development and superior corrosion resistance, were used to cement calcareous sand (CS) and to investigate its mechanical and microstructural characteristics under different water environments. Unconfined compressive strength tests (UCS) showed that SC-CS and FC-CS could meet subgrade requirements at 1 d and 7 d, with SC-CS and FC-CS reaching 3.12 MPa and 3.44 MPa at 1 d, and 3.26 MPa and 3.67 MPa at 7 d, respectively, under seawater SS conditions. Seawater mixing and immersion were found to promote the early strength and stiffness development of both SC-CS and FC-CS, with a more pronounced effect observed for FC-CS. Based on experimental results, a damage model for the stabilized specimens was established with a fitting accuracy of R² > 0.97. This constitutive model accurately describes the stress–strain relationship of the material and quantitatively characterizes its damage evolution. Microscopic XRD and SEM analyses indicated that the main hydration product in freshwater-cured specimens was ettringite, and the interparticle connection of CS was dominated by bridging through rod-like ettringite. In contrast, under seawater conditions, the ettringite content decreased, while hydrotalcite and calcium aluminate hydrate increased, forming massive and lamellar bridging products. Compared with SC-CS, the bridging structure in FC-CS was denser. Moreover, the compactness of the bridging structure not only affected its mechanical properties but also governed the movement mode of CS particles, thereby influencing the damage evolution and failure mode of the specimens. The findings provide theoretical support for the construction needs of island road. Full article

Corrosion of steel pipe specimens in marine environments plays a critical role in the durability and service-life design of coastal and offshore structures. In Vietnam, the scarcity of long-term field corrosion data necessitates the application of accelerated testing and statistical modeling to characterize corrosion degradation. In this study, a two-parameter Weibull model is employed to describe the time-dependent corrosion mass loss of steel pipe specimens under simulated Vietnamese marine conditions. Accelerated corrosion tests are conducted using an impressed current technique in artificial seawater, and equivalent exposure durations ranging from 4.5 to 100 years are determined based on Faraday’s law. This conversion is based on the assumption of uniform corrosion and constant electrochemical conditions, which may not fully represent real marine environments. The Weibull parameters are calibrated using early-stage corrosion data, yielding a shape parameter k = 1.226 and a scale parameter η = 70.761 years. Comparison with experimental results indicates that the model captures the monotonic increase in cumulative corrosion mass loss, although it overestimates the measurements at intermediate exposure durations. The validation results show prediction errors of MAE = 13.06% and RMSE = 14.13%, while sensitivity analysis reveals that long-term predictions are more sensitive to the shape parameter than to the scale parameter. This study also discusses the limitations of using accelerated corrosion testing and Faraday’s law for scaling to long-term predictions, particularly regarding differences in corrosion product morphology and the impact of real-world environmental variability. The calibrated Weibull model provides a statistical approximation for durability assessment of steel pipe structures under Vietnamese marine conditions, particularly in cases where long-term field corrosion data are unavailable. Full article

In nuclear power, marine engineering, and other fields, a matching system composed of duplex steel and copper alloy is a common combination for rotating components in a seawater environment. However, this system is susceptible to galvanic corrosion that seriously threatens its service safety and service life, with ZCuAl10Fe5Ni5 being the main component corroded. Additionally, current corrosion research on this system has evident gaps. Specifically, the influence of area ratio on galvanic corrosion remains insufficiently understood, and the action mechanism of Cl⁻ on the ZCuAl10Fe5Ni5-based corrosion product film in seawater, as well as the product evolution path, has not been fully revealed, which restricts the development of targeted protection technologies. This study explores the degradation mechanism of ZCuAl10Fe5Ni5 in a specific high-salinity environment (20,000 mg/L Cl⁻), characteristic of nuclear power plant service conditions. The results show that due to the significant electrode potential difference between the SAF2507 duplex steel and ZCuAl10Fe5Ni5 copper alloy, a stable galvanic couple is formed, with ZCuAl10Fe5Ni5 acting as the anode and undergoing dissolution corrosion. When the area ratio of ZCuAl10Fe5Ni5 (anode) to SAF2507 duplex steel (cathode) is 1:50, a significantly stronger galvanic effect is observed. The high concentration of Cl⁻ in seawater can damage the surface of the ZCuAl10Fe5Ni5-based corrosion product film, leading to intensified local corrosion. The ZCuAl10Fe5Ni5-derived corrosion products have a layered structure mainly comprising a mixed system of Cu-Al-Mg oxides/hydroxides, and the corrosion process is accompanied by selective aluminum depletion corrosion. This study provides insight into the corrosion mechanism and key influencing factors of ZCuAl10Fe5Ni5 in the matching system, as well as a theoretical basis and technical support for the design of compatibility metal materials in a seawater environment and the control of corrosion in ZCuAl10Fe5Ni5. Full article

An experimental investigation was conducted to examine the resistance to sulfate attack and chloride ion diffusion of concrete incorporating multiple industrial wastes (MIWC), including limestone powder (LP), tailings sand, and silica fume (SF). The degradation mechanisms of the MIWC under coupled sulfate wet–dry cycles and chloride ion penetration are systematically revealed. Nine concrete mixtures were designed with variable water-to-binder (w/b) ratios, LP contents, SF dosages, and tailings sand/machine-made sand ratios. The results indicate that reducing the w/b ratio significantly enhances resistance to sulfate attack and chloride penetration. A moderate LP dosage optimizes pore structure and improves long-term sulfate resistance, whereas SF effectively refines the pore matrix and reduces the chloride diffusion coefficient. The coupled action of chloride and sulfate accelerates early-stage pore filling by corrosion products but promotes later-stage cracking because of expansive erosion products. A modified sulfate damage model and a multifactor coupled chloride diffusion model are established, which consider damage evolution, chloride binding, and time-dependent diffusivity. The predicted service life of the MIWC under marine exposure is in reasonable agreement with the experimental trends. This work provides a theoretical basis for durable design and industrial waste utilization in marine concrete structures. Full article

The Lower Permian M Formation marine carbonate gas reservoir in Block X of the Sichuan Chongqing exploration area has extreme working conditions with moderate H₂S content (0.57%–0.97%), moderate CO₂ content (2.59%–5.59%), and high formation pressure (70–80 MPa). Gas wells face challenges such as multi medium synergistic corrosion, large productivity differences, and limited economic viability. This article addresses the above issues for the first time by analyzing the dual corrosion mechanism, selecting corrosion-resistant pipes (nickel-based alloys/nickel–tungsten alloy coatings), evaluating the adaptability of corrosion inhibitor processes, and real-time monitoring and warning of corrosion risks. A collaborative anti-corrosion technology system of “mechanism material process monitoring” is constructed, and the first successful field implementation was carried out in this block. The experiment shows that the uniform corrosion rate of nickel–tungsten alloy coating under extreme working conditions (122 °C/85 MPa) is only 0.004 mm/a, which is more economical than traditional nickel-based alloys (cost reduction of 69%); CT2 series corrosion inhibitors can selectively inhibit the corrosion rate of gas wells with different water contents (efficiency > 82%). The combination of electromagnetic flaw detection and multi arm wellbore logging technology has achieved dynamic monitoring of downhole pipe corrosion. This system has been successfully applied in seven gas wells in Block X, achieving controllable corrosion risks, cost reduction and efficiency improvement, and providing a replicable technical paradigm for the safe and economic development of marine high-sulfur gas reservoirs. Full article

In marine service environments, material surfaces inevitably suffer from wear damage, which can compromise the integrity of protective coatings and further affect their corrosion resistance. Therefore, investigating the post-wear corrosion resistance of coatings is of great significance. In this work, single-layer CrN coatings, CrAlN coatings, and CrN/CrAlN multilayer coatings were deposited on stainless-steel substrates by arc ion plating, and the microstructure, tribological properties, and corrosion behavior before and after wear were systematically investigated. Wear tests were performed under applied loads of 2.5 N and 5 N. The corrosion behavior in the unworn condition and the post-wear corrosion resistance condition was evaluated in a 3.5 wt.% NaCl solution. The results showed that all coatings exhibited a face-centered cubic (FCC) structure, while the CrN/CrAlN multilayer coating possessed the smallest average grain size (13.47 nm). Under applied loads of 2.5 N and 5 N, the CrN/CrAlN multilayer coating exhibited the lowest wear rate, indicating the best wear resistance. In the unworn condition, the CrN/CrAlN multilayer coating showed the lowest corrosion current density (2.74 × 10⁻¹⁰ A/cm²) and the most positive corrosion potential (0.025 V), demonstrating the best corrosion resistance. After wear under a load of 5 N, the CrN/CrAlN multilayer coating retained a low corrosion current density (3.35 × 10⁻¹⁰ A/cm²), in contrast to the marked increases observed for the single-layer coatings. The enhanced performance is considered to be mainly associated with the periodic heterogeneous interfaces in the multilayer structure, which help suppress crack propagation and prolong the penetration path of corrosive media. Full article