Search Results (116)

Microbiologically influenced corrosion (MIC) represents a critical challenge to the integrity of pipelines, piping, and metal structures in offshore environments, directly affecting the safety and operational costs of companies in the energy sector. However, conventional control methods, such as the use of chemical inhibitors, raise environmental and economic concerns. To face this problem, a biosurfactant produced by Pseudomonas cepacia CCT 6659 was tested as a biocorrosion inhibiting agent on carbon steel specimens immersed in seawater. For this purpose, static and dynamic conditions were simulated using different concentrations of the biosurfactant. Furthermore, analyses were performed using Scanning Electron Microscopy paired with Energy Dispersive Spectroscopy (SEM/EDS) to visualize the morphology of the biofilm and its chemical components. Laboratory tests indicated that the biosurfactant formulated in a 1:5 (v/v) ratio reduced the mass loss of test specimens (119.72 ± 2.64 g/m²) by no less than 57.3% compared to the control (280.28 ± 4.58 g/m²). Under dynamic conditions, the 1:2 (v/v) formulation showed greater protection, being able to reduce specimen corrosion (578.87 ± 7.01 g/m²) by 69.6% compared to the control (1901.41 ± 13.53 g/m²). SEM/EDS analyses revealed changes in surface composition and a reduction in corrosive elements associated with sulfur in the formed biofilms, which may be associated with a decrease in sulfate-reducing bacteria (SRB) activity, suggesting microbial inhibition by the biosurfactant. The results obtained in this study highlight the biosurfactant as a viable and ecological alternative to synthetic inhibitors, with potential application in the protection of metal structures exposed to corrosive environments in offshore energy systems, promoting greater durability, sustainability, and less environmental impact. Full article

In the medical field, magnesium (Mg) alloys have been widely used due to their excellent antibacterial properties and biodegradability. However, in the marine environment, the antibacterial effect may be greatly attenuated, and consequently, microorganisms in the ocean are likely to adhere to the surface of Mg alloys, resulting in biocorrosion damage, which is really troublesome in the maritime industry and can even be disastrous to the navy. Currently, there is a lack of research on the biocorrosion of Mg alloys that may find important applications in marine engineering. In this paper, the biocorrosion mechanism of the Mg alloy Mg-3Nd-2Gd-Zn-Zr caused by Chlorella vulgaris (C. vulgaris), a typical marine microalga, was studied. The results showed that the biomineralization process in the artificial seawater containing a low concentration of C. vulgaris cells was accelerated compared with that in the abiotic artificial seawater, leading to the deposition of CaCO₃ on the surface to inhibit the localized corrosion of the Mg alloy, whereas a high concentration of C. vulgaris cells produced a high content of organic acids at some sites through photosynthesis to significantly accelerate the surface film rupture at some sites and severe localized corrosion there, but meanwhile, it resulted in the formation of a more protective biomineralized film in the other areas to greatly alleviate the corrosion. The contradictory biocorrosion behaviors on the Mg-3Nd-2Gd-Zn-Zr alloy induced by C. vulgaris were finally explained by a mechanism proposed in the paper. Full article

Background/Objectives: Biocorrosion, driven by microbial colonization and biofilm formation, poses a significant threat to the integrity of metal artifacts, particularly those composed of copper and its alloys. Pseudomonas aeruginosa, a bacterial species that reduces nitrates, plays a key role in this process. This study explores the potential of two metabolite-rich plant extracts, Aloe vera and Opuntia ficus-indica, as sustainable biobased inhibitors of microbial-induced corrosion (MICOR). Methods: The antibacterial and antibiofilm activities of the extracts were evaluated using minimal inhibitory concentration (MIC) assays, time-kill kinetics, and biofilm prevention and removal tests on copper, bronze, and brass samples. Spectrophotometric and microbiological methods were used to quantify bacterial growth and biofilm density. Results: Both extracts exhibited significant antibacterial activity, with MIC values of 8.3% (v/v). A. vera demonstrated superior bactericidal effects, achieving reductions of ≥3 log₁₀ in bacterial counts at lower concentrations. In antibiofilm assays, both extracts effectively prevented biofilm formation and reduced established biofilms, with A. vera exhibiting greater efficacy against them. The active metabolites—anthraquinones, phenolics, flavonoids, and tannins—likely contribute to these effects. Conclusions: These findings highlight the dual role of A. vera and O. ficus-indica extracts as both corrosion and biocorrosion inhibitors. The secondary metabolite profiles of these plants support their application as eco-friendly alternatives in the conservation of metal cultural heritage objects. Full article

To enhance the resistance of stainless steel (SS) against biofouling and biocorrosion, hyperbranched poly(viologen) brushes were covalently immobilized onto SS substrates. This study systematically evaluated the efficacy of the functionalized SS substrates in inhibiting microorganism adhesion, biofouling and biocorrosion. Enhanced antifouling and antimicrobial properties were evidenced through assays involving the attachment of Amphora coffeaeformis, the settlement of Pseudomonas sp. bacteria and barnacle cyprids. Furthermore, the functionalized SS substrates demonstrated superior antifouling performance alongside excellent biocorrosion–inhibition properties. These findings suggest that the functionalized SS substrates, with their robust antimicrobial, antifouling and anticorrosion capabilities, hold significant potential for applications in aquatic environments Full article

This study tested the effectiveness of a bifunctional polysiloxane (L43) as a means of protecting concrete surfaces from biocorrosion. L43 was designed to contain two types of functional groups in its structure: surface-active hydrophobic chains and hydrophilic groups that allow the coating to permanently bond to the concrete. L43-coated cement samples achieved compressive strengths exceeding 70 MPa, while samples subjected to cyclic freeze–thaw tests achieved compressive strengths exceeding 33 MPa. In addition, compound L43 at a concentration of 5% reduced the photosynthetic activity of microalgae cells on the concrete surface. The maximum value of chlFI decreased by 69.5%, while the average value decreased by 71.4%. Thus, it was proven that compound L43 effectively counteracts biological corrosion without deteriorating the structure of the impregnated substrate. It should be emphasized that the biocidal effect is due to the structure of the siloxane compound and appropriately selected functional groups. There is no need to add harmful biocides, making the solution environmentally friendly. In addition, the coating allows for free air circulation, which is crucial for the protection of building and construction materials. Full article

Additive manufacturing brings many benefits to the building industry, one of them being automatization and the possibility to work in harsh environments, including underwater applications. In addition, this technology enables faster infrastructure repairs and adjustments to the scope of work to specific damage caused by, for example, biocorrosion processes. The main aim of this article is to investigate the development of geopolymers as a printable material for civil engineering, including underwater applications. For that purpose, the process of the material extrusion will be modified, and material properties will be improved. In the first step, the raw materials were investigated (SEM, EDS, XRF, particle size analysis) and the proper additives were selected based on literature analysis. Next, geopolymer paste was synthesized and fresh paste properties were investigated, including time for curing samples and workflow. The mixture composition was modified to obtain the required printable parameters through the application of different additives and the modification of the proportion of components, especially alkali solution. Finally, small-scale additive manufacturing trials were conducted in the air and with submerged containers. Additionally, samples were prepared using the casting method to compare the mechanical properties and microstructure. The obtained results show that additives such as xanthan gum and superplasticizer improve the rheological properties of the paste efficiently. With the help of additive manufacturing, geopolymer samples with compressive strengths of up to 7.5 MPa and flexural strengths of up to 4.15 MPa after 28 respectively were achieved. Compared to the average of the cast samples, the compressive strength of the printed samples was at least 5% lower, while the flexural strength was at least 38% lower for printed samples. The 3D-printed samples showed strong anisotropy between the tested orientations of the flexural strength samples. Full article

Microorganisms play a significant role in biofouling and biocorrosion within the maritime industry. Addressing these challenges requires an innovative and integrated approach utilizing marine natural products with beneficial properties. A comprehensive screening of 173 non-toxic EtOAc and H₂O extracts derived from diverse marine organisms collected in Indonesian waters was conducted using a robust panel of assays. These included antimicrobial tests and classical biosurfactant assays (drop collapse and oil displacement), as well as anti-quorum-sensing (QS) and anti-biofilm assays. These screening efforts identified five active extracts with promising activities. Among these, EtOAc extracts of the marine tunicate Sigilina cf. signifera (0159-22e) and the marine sponge Lamellodysidea herbacea (0194-24c) demonstrated significant anti-biofouling activity against Perna indica and anti-biocorrosion performance (mpy 10.70 ± 0.70 for S. cf. signifera; 7.87 ± 0.86 for L. herbacea; 13.60 ± 1.70 for positive control Tetracorr CI-2915). Further chemical analyses of the active extracts, including LC-HR-MS/MS, MS-based molecular networking, and chemoinformatics, revealed the presence of both known and new bioactive compounds. These included tambjamines and polybrominated diphenyl ethers (PBDEs), which are likely contributors to the observed bioactivities. Subsequent investigations uncovered new anti-QS and anti-biofilm properties in synthetic and natural PBDEs 1–12 previously derived from L. herbacea. Among these, 8 exhibited the most potent anti-QS activity, with an IC₅₀ value of 15 µM, while 4 significantly reduced biofilm formation at a concentration of 1 µM. This study highlights the potential of marine-derived compounds in addressing biofouling and biocorrosion challenges in a sustainable and effective manner. Full article

Given the increasing demand for biocompatible implant materials in regenerative engineering, novel surface modification techniques are essential to enhance tissue integration, durability, and corrosion resistance. This study investigates the application of plasma electrolytic oxidation (PEO), a high-voltage anodic oxidation technique, for the surface modification of magnesium (Mg) implants. The research emphasizes both functionality enhancement and process sustainability, adhering to green chemistry principles. A comprehensive analysis was conducted to evaluate the physicochemical and biological properties of the modified surfaces. The chemical structure of the coatings was characterized using Fourier-transform infrared spectroscopy (FT-IR) and atomic absorption spectroscopy (ASA). Surface morphology and composition were examined via scanning electron microscopy (SEM), while wettability was assessed through contact angle measurements. Additionally, biodegradation and biocorrosion studies were performed to evaluate stability, and cytotoxicity was tested using MG-63 human osteosarcoma cells. Results demonstrated that carefully optimized PEO process parameters, combined with appropriate electrolyte compositions, enabled the formation of MgO coatings with significantly enhanced stability, reduced biocorrosion, and improved biocompatibility. These findings indicate the potential of surface-modified magnesium implants for advanced biomedical applications. Full article

Hydrocarbon fuel biofouling and biocorrosion require expensive cleanup of aviation infrastructures unless appropriate sustainment measures are applied. The identification of novel biological control agents offers promising alternatives to the current chemical biocides used in fuel sustainment. In this study, 496 microbial fuel isolates from our in-house repository were screened to identify new endogenously produced antimicrobial compounds. Using agar plug screening, liquid culture growth testing, and Jet A fuel culture assays, the two fuel-isolate strains Pseudomonas protegens #133, and Bacillus subtilis #232 demonstrated promising biocontrol activity against bacteria, yeast, and filamentous fungi. Liquid chromatography-quadrupole time of flight tandem mass spectrometry (LC-QTOF-MS/MS) of #232 culture filtrate identified several common lipopeptide antimicrobials including gageostatin C, gageopeptin B, and miscellaneous macrolactins. In contrast, LC-QTOF-MS/MS identified the siderophore pyochelin as one of the predominant compounds in #133 culture filtrate with previously demonstrated antimicrobial effect. Jet fuel microbial consortium culture testing of #133 culture filtrate including flow-cytometry live/dead cell mechanism determination demonstrated antimicrobial action against Gram-positive bacteria. The study concludes that antimicrobial compounds secreted by #133 have bactericidal effects against Gordonia sp. and cause cell death through bacterial lysis and membrane damage with potential applications in the biocidal treatment of hydrocarbon-based aviation fuels. Full article

This study aimed to develop a novel type of biodegradable magnesium (Mg)-based implant with enhanced biological activity through surface modification using plasma electrolytic oxidation (PEO) combined with the incorporation of rare earth ions (Eu and Gd). Magnesium is recognized for its lightweight nature, biocompatibility, and bone-like mechanical properties, making it a promising alternative to titanium implants. Unlike titanium, Mg-based biomaterials can be safely used in pediatric surgery due to their ability to degrade naturally within the body. However, pure magnesium is highly reactive in physiological fluids, necessitating surface modifications to mitigate biocorrosion prior to clinical application. To address this challenge, the PEO process was employed, resulting in surface passivation and the formation of a protective coating. Experimental evaluations demonstrated reduced biodegradation rates and magnesium ion release, confirming the beneficial role of rare earth elements in decreasing reactivity. Wettability tests indicated high hydrophilicity, while scanning electron microscopy (SEM) revealed appropriate surface morphology and element deposition conducive to bone regeneration. Electrochemical analyses further validated the protective efficacy of the magnesium oxide layers enhanced with rare earth ions. Finally, in vitro cytotoxicity tests on the MG-63 osteosarcoma cell line confirmed the biocompatibility of the modified magnesium implants. Overall, this study highlights the potential of Mg-based biomaterials, modified through PEO and rare earth ion incorporation, for use in medical implants. Full article

This paper presents the results of microbial corrosion tests on M0-grade copper under conditions simulating a geological repository for radioactive waste at the Yeniseisky site (Krasnoyarsk Krai, Russia). The work used a microbial community sampled from a depth of 450 m and stimulated with glucose, hydrogen and sulfate under anaerobic conditions. It was shown that the maximum corrosion rate, reaching 9.8 µm/y, was achieved with the addition of sulfate (1 g/L) with the participation of microorganisms from the families Desulfomicrobiaceae, Desulfovibrionaceae and Desulfuromonadaceae. It was noted that the most important factor leading to copper corrosion was the accumulation of hydrogen sulfide during the activation of sulfate-reducing microorganisms of the genera Desulfomicrobium, Desulfovibrio and Desulfuromonas. During the development of the microbial community under these conditions, the content of copper can have a significant toxic effect at a concentration of more than 250 mg/L. Full article

Magnesium and its alloys represent promising candidates for biomedical implants due to their biodegradability and mechanical properties, which are similar to natural bone. However, their rapid degradation process characterized by dynamic pH fluctuations and significant hydrogen gas evolution during biocorrosion adversely affects both in vitro and in vivo assessments. While the ISO 10993-5 and 12 standards provide guidelines for evaluating the in vitro biocompatibility of biodegradable materials, they also introduce testing variability conditions that yield inconsistent results. To address these inherent characteristics of Mg alloys, developing improved methods that accurately simulate the physiological environment for in vitro biocompatibility testing is essential. This study introduces two novel extraction approaches for evaluating Mg alloys: a buffered solution utilizing PBS/DMEM with quaternary dilutions and a modified ISO standard protocol employing decuple dilution of conventional unbuffered extracts. The present findings establish that controlled optimization of extraction conditions, specifically buffer composition and dilution parameters, enables reliable in vitro cytotoxicity assessment of Mg alloys, providing a robust methodology that advances the preclinical evaluation of these promising biodegradable materials. Full article

The effects of medium and flow rate on the film-forming structures of B10 Cu-Ni alloys and their resistance to corrosion caused by sulfate-reducing bacteria are investigated in this article. Combined with a predicted cloud map of pipeline corrosion area and a particle motion trajectory map obtained using Computational Fluid Dynamics (CFD), the growth law of alloy passivation films was analyzed and the pitting process of sulfate-reducing bacteria (SRB) on passivation films was revealed. The results show that the film formation effect is best when the stream of water in the film-forming environment is filtered seawater with a flow rate of 0.8 m/s, which consists of a uniform and dense gray-brown passivated film layer with the strongest resistance to SRB corrosion. When the flow rate is 0 m/s, the clay particles in the seawater cover the surface of the passivation film, hindering the contact of oxygen with the substrate and inhibiting the growth of the passivation film. When the stream of water in the film-forming environment is seawater with a flow rate of 3 m/s, the surface of the substrate shows obvious scouring marks, which is favorable for the enrichment of SRB and further accelerates the pitting corrosion of the substrate. Cl⁻ has a significant influence on the formation of passivation films on B10 Cu-Ni alloys. When the filming medium is deionized water, the B10 Cu-Ni alloy does not form a complete passivation film at all flow rates. Full article

Microbially influenced corrosion poses a significant threat to the integrity and longevity of carbon steel infrastructure, particularly in environments conducive to biofilm formation by thiosulfate-reducing bacteria (TRB) to carbon steel. This study explores the potential of Portulaca oleracea, an edible plant species, as a dual-action biocide and green corrosion inhibitor for mitigating MIC adhesion. Through a comprehensive suite of experimental and analytical techniques, including electrochemical analysis, microbial analysis, gravimetric methods, and surface characterization, the efficacy of Portulaca oleracea extract is evaluated for its ability to inhibit TRB growth and biofilm formation while concurrently providing corrosion protection to carbon steel substrates. The electrochemical analyses reveal the extract’s capacity with the anodic reaction inhibition achieving 80%, thereby reducing the overall corrosion rate of carbon steel in the presence of TRB biofilms. Complementary microbial analyses, such as viable cell counting using test kits, elucidate the biocidal action of the extract, effectively suppressing TRB growth and biofilm development, with the presence of 20 ppm of the extract reducing bacterial growth. Surface characterization techniques provide insights into the adsorption behavior of the extract’s constituents on the carbon steel surface, forming a protective film that mitigates corrosion and biofilm adhesion. The adsorption of the extract at the interface between mild steel and the formation water adheres to Langmuir isotherm. Overall, the biocorrosion issue we are addressing in this work is crucial for ensuring the sustainability and efficiency of equipment, pipelines, and other metal-based systems. Full article

In this study, recycled acrylonitrile-butadiene-styrene terpolymer (ABSr) was reused to produce polyamide 6 (PA6)-based blends. This was achieved through reactive compatibilization using styrene-acrylonitrile-maleic anhydride (SAN-g-MA) copolymer with a high degree of functionalization (6–10% MA). The PA6/ABSr and PA6/ABSr/SAN-g-MA blends were prepared through melt processing and injection molding and then analyzed for their rheological, mechanical, thermomechanical, thermal, and structural properties, as well as morphology. The torque rheometry revealed a maximum reactivity of the PA6/ABSr (70/30 wt%) blend with low SAN-g-MA (5 phr—parts per hundred resin) content, while above this threshold, torque began to decline, indicating compatibilizer saturation in the interface. These findings were further substantiated by the increase in complex viscosity and the lower melt flow index (MFI) of the PA6/ABSr/SAN-g-MA (5 phr) blend. The 5 phr SAN-g-MA reactive compatibilization of the PA6/ABSr blends significantly enhanced its impact strength, elongation at break, tensile strength, and heat deflection temperature (HDT) by 217%, 631%, 12.6%, and 9.5%, respectively, compared to PA6/ABSr. These findings are promising for the plastic recycling field, paving the way for the production of new tailor-made materials at a reduced price. Full article