The effect of sulphate-reducing bacteria biofilm on passivity and development of pitting on 2205 duplex stainless steel

Effects of marine eutrophication environment on microbial corrosion: A review

Metal materials undergo severe corrosion in eutrophic environments. The effect of DO decay stimulated by high concentrations of nitrogen and phosphorus pollutants on microorganisms leads to the coupling of electrochemical and microbial corrosion processes. However, there are few studies on microbial corrosion mechanisms in eutrophic environments. This article discusses the corrosive factors of marine eutrophication, summarizes the impact of marine eutrophication on microbial corrosion and the potential mechanisms, including aerobic biofilm corrosion, aerobic & anaerobic mixed biofilm corrosion, and anaerobic microbial electron transfer corrosion, and expounds on the research methods for microbial corrosion of materials serving in estuarine areas prone to pollution. Microbial prevention and control, such as nutrient restriction and microbial interspecies competition, are of research value in the field of green protection. Microbial corrosion mechanisms studies in marine eutrophication environments are significant for environment monitor development, water intake and algae control technologies, and corrosion protection in polluted environments.

Corrosion of Q235 carbon steel induced by sulfate-reducing bacteria in groundwater: corrosion behavior, corrosion product, and microbial community structure

Microbiologically influenced corrosion (MIC) is one of the reasons leading to the service failure of pipelines buried in the soil. In this work, the effect of sulfate-reducing bacteria (SRB) on the corrosion behavior of Q235 carbon steel in groundwater was investigated by electrochemical methods, surface analysis, and biological analysis. The results show that SRB utilizes iron as electron donor to sustain the vital activities of organic carbon-starved groundwater during the 14-day experimental period. The microbial community composition analysis at the genus level demonstrate that the diversity and richness decrease after corrosion, and the dominant SRB species has changed from Desulfovibrio to Desulfosporosinus. Moreover, the impedance of the carbon steel in the presence of biofilm was 1 order of magnitude higher than that of other periods in the electrochemical test, indicating that the biofilm and formed ferrous sulfide layer impeded the occurrence of corrosion. Although the 3D topography indicated that the surface of carbon steel was more uneven and pits were increased in the presence of SRB, the average weight loss (0.0396 ± 0.0050 g) was much higher than that without SRB (0.0139 ± 0.0007 g). These results implied that the growth of SRB makes the corrosion process of Q235 carbon steel more complicated.

Characterization of the biofilm structure and microbial diversity of sulfate-reducing bacteria from petroleum produced water supplemented by different carbon sources

Colonization by sulfate-reducing bacteria (SRB) in environments associated with oil is mainly dependent on the availability of sulfate and carbon sources. The formation of biofilms by SRB increases the corrosion of pipelines and oil storage tanks, representing great occupational and operational risks and respective economic losses for the oil industry. The aim of this study was to evaluate the influence of the addition of acetate, butyrate, lactate, propionate and oil on the structure of biofilm formed in carbon steel coupons, as well as on the diversity of total bacteria and SRB in the planktonic and sessile communities from petroleum produced water. The biofilm morphology, chemical composition, average roughness and the microbial diversity was analyzed. In all carbon sources, formation of dense biofilm without morphological and/or microbial density differences was detected, with the most of cells observed in the form of individual rods. The diversity and richness indices of bacterial species in the planktonic community was greater than in the biofilm. Geotoga was the most abundant genus, and more than 85% of SRB species were common to all treatments. The functional predicted profile shown that the observed genres in planktonic communities were related to the reduction of sulfate, sulfite, elementary sulfur and other sulfur compounds, but the abundance varied between treatments. For the biofilm, the functions predicted profile for the oil treatment was the one that most varied in relation to the control, while for the planktonic community, the addition of all carbon sources interfered in the predicted functional profile. Thus, although it does not cause changes in the structure and morphology biofilm, the supplementation of produced water with different carbon sources is associated with changes in the SRB taxonomic composition and functional profiles of the biofilm and the planktonic bacterial communities.

Development of Antibacterial V/TiO2-Based Galvanic Coatings for Combating Biocorrosion

Recently, TiO₂ crystals have been modified by transition-metal dopants with different physicochemical structures to attain distinguished properties. Considering the similar ionic sizes of V⁴⁺ (0.058 nm) and Ti⁴⁺ (0.061 nm), vanadium in the +4 state can be effectively incorporated into the crystal lattice of TiO₂ to tune the band gap energy by creating an impurity energy level (V⁵⁺/V⁴⁺) below the conduction band (2.1 eV) and retaining the anatase phase. In vanadium-incorporated TiO₂ (V/TiO₂), V⁴⁺ is a good dopant candidate as it can increase the lifetime of the charge carrier and reduce the electron-hole recombination rate, which results in high antibacterial activity under visible light irradiation. The present study explores the V/TiO₂-based hot-dip zinc coating with enhanced electrochemical properties and long-term stability for combating biocorrosion. All the composites and the coatings are characterized by different techniques, including X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray analysis, confocal laser scanning microscopy, optical surface profilometry, and X-ray photoelectron spectroscopy. The biofilm formation assay and the cell viability assay reveal that the tuned composition of the V/TiO₂-based hot-dip zinc coating effectively kills the adherent bacteria and inhibits biofilm formation on the surface. The high-charge-transfer resistance (225.67, 223.63, and 242.35 Ω cm²) and the high-inhibition efficiency (92.24, 92.30, and 92.02%) of the tuned composition of the V/TiO₂-based hot-dip zinc coating confirm its efficient and sustainable antibiocorrosion performance and long-term stability even after an exposure period of 21 days in different bacterial environments. With the inherent antibacterial properties and antibiocorrosion performance of the developed V/TiO₂-based hot-dip zinc coating, the mild steel substrates can find potential application in different fields, including aquatic and marine environments.

Microbial corrosion of metals: The corrosion microbiome

Microbially catalyzed corrosion of metals is a substantial economic concern. Aerobic microbes primarily enhance Fe⁰ oxidation through indirect mechanisms and their impact appears to be limited compared to anaerobic microbes. Several anaerobic mechanisms are known to accelerate Fe⁰ oxidation. Microbes can consume H₂ abiotically generated from the oxidation of Fe⁰. Microbial H₂ removal makes continued Fe⁰ oxidation more thermodynamically favorable. Extracellular hydrogenases further accelerate Fe⁰ oxidation. Organic electron shuttles such as flavins, phenazines, and possibly humic substances may replace H₂ as the electron carrier between Fe⁰ and cells. Direct Fe⁰-to-microbe electron transfer is also possible. Which of these anaerobic mechanisms predominates in model pure culture isolates is typically poorly documented because of a lack of functional genetic studies. Microbial mechanisms for Fe⁰ oxidation may also apply to some other metals. An ultimate goal of microbial metal corrosion research is to develop molecular tools to diagnose the occurrence, mechanisms, and rates of metal corrosion to guide the implementation of the most effective mitigation strategies. A systems biology approach that includes innovative isolation and characterization methods, as well as functional genomic investigations, will be required in order to identify the diagnostic features to be gleaned from meta-omic analysis of corroding materials. A better understanding of microbial metal corrosion mechanisms is expected to lead to new corrosion mitigation strategies. The understanding of the corrosion microbiome is clearly in its infancy, but interdisciplinary electrochemical, microbiological, and molecular tools are available to make rapid progress in this field.

Issues of Corrosion and Degradation under Dusty Deposits of Energy Biomass

The aim of the study is to identify and determine the role of microbial degradation taking place in dusty deposits in potential threats (i.e., destruction of protective coatings and development of corrosion) to the means of transport in conditions of transshipment of energy biomass. This paper presents the results of research on the impact of powdery fractions of wood biomass and biomass obtained from oil plants in the degradation of paint coatings and corrosion processes. During the research, exposure to simulated port climate, OM, SEM, and EDS studies were used. It has been found that the presence of the fraction containing protein compounds and amino acids (e.g., dust of rapeseed meal) stimulates the growth of microorganisms whose metabolism products favour the destruction of protective coatings and the development of corrosion. Under the same conditions, the destruction of protective zinc coatings has been observed. It was found that already 14 days of exposure to oily biomass deposits results in damage to paint coatings caused by microbiological processes. The 8-week exposure causes serious degradation of protective coatings and the base material itself. The biomass of wood origin, containing compounds of the tannin type, did not show as much aggressive activity as the biomass with protein compounds.

Microbial corrosion of initial perforation on abandoned pipelines in wet soil containing sulfate-reducing bacteria

In this work, the microbial corrosion inside a perforation on an X52 pipeline steel was investigated in wet soil containing sulfate-reducing bacteria (SRB) by biotesting, electrochemical measurements, including open-circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization, and surface analysis techniques such as 3D topographic imaging, scanning electron microscopy and energy-dispersive x-ray spectrum. Results show that the further corrosion rate of the initial perforation on pipelines is not uniform along its depth direction, and the corrosion kinetics depends on the availability of microorganism such as SRB in the environment. In abiotic environments, the perforation close to the solution side corrodes more rapidly than that at the soil side. However, in SRB-containing environments, the corrosion kinetics is different, where the middle of perforation possesses the greatest corrosion rate, which is attributed to the microbially accelerated corrosion. There are generally more sessile SRB cell counts on the steel near the solution phase than that at the soil side. The corrosion of the perforation could be attributed to the high counts of sessile SRB cells and their starvation effect, making the SRB extract electrons directly from the steel.

Microbiologically influenced corrosion of marine steels within the interaction between steel and biofilms: a brief view

Marine is the harshest corrosive environment where almost all marine underwater equipment and facilities undergo corrosion caused by marine microorganisms. With the development of marine resources globally, the marine engineering and relevant infrastructures have increased exponentially. Microbiologically influenced corrosion (MIC) leads to severe safety accidents and great economic losses. The specific aggregation of corrosive microbial communities and their interactions with materials conform to a typical ecological adaptation mechanism. On the one hand, corrosive biofilms in the marine environment selectively colonize on a specific steel substrate by utilizing their complex community composition and various extracellular polymeric substances; on the other hand, the elemental composition and surface microstructure of different engineering steels affect the microbial community and corrosive process. MIC in the marine environment is a dynamic process evolving with the formation of corrosive biofilms and corrosion products. In this mini-review, the interactions between corrosive biofilm and steel substrates are explored and discussed, especially those conducted in situ in the marine environment. Herein, the important role of iron in the dynamic process of marine corrosion is highlighted.

Corrosion effect of Bacillus cereus on X80 pipeline steel in a Beijing soil environment

The corrosion of X80 pipeline steel in the presence of Bacillus cereus (B. cereus) was studied through electrochemical and surface analyses and live/dead staining. Scanning electron microscopy and live/dead straining results showed that a number of B. cereus adhered to the X80 steel. Electrochemical impedance spectroscopy showed that B. cereus could accelerate the corrosion of X80 steel. In addition, surface morphology observations indicated that B. cereus could accelerate pitting corrosion in X80 steel. The depth of the largest pits due to B. cereus was approximately 11.23μm. Many pits were found on the U-shaped bents and cracks formed under stress after 60days of immersion in the presence of B. cereus. These indicate that pitting corrosion can be accelerated by B. cereus. X-ray photoelectron spectroscopy results revealed that NH₄⁺ existed on the surface of X80 steel. B. cereus is a type of nitrate-reducing bacteria and hence the corrosion mechanism of B. cereus may involve nitrate reduction on the X80 steel.

Ennoblement, corrosion, and biofouling in brackish seawater: Comparison between six stainless steel grades

In this work, six common stainless steel grades were compared with respect to ennoblement characteristics, corrosion performance and tendency to biofouling in brackish sea water in a pilot-scale cooling water circuit. Two tests were performed, each employing three test materials, until differences between the materials were detected. Open circuit potential (OCP) was measured continuously in situ. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements were conducted before and after the tests. Exposed specimens were further subjected to examinations by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), and the biofouling was studied using epifluorescence microscopy, quantitative polymerase chain reaction (qPCR) and high-throughput sequencing (HTP sequencing). The results revealed dissimilarities between the stainless steel grades in corrosion behaviour and biofouling tendency. The test material that differed from the most of the other studied alloys was grade EN 1.4162. It experienced fastest and most efficient ennoblement of OCP, its passive area shrank to the greatest extent and the cathodic reaction was accelerated to a significant degree by the development of biofilm. Furthermore, microbiological analyses revealed that bacterial community on EN 1.4162 was dominated by Actinobacteria, whereas on the other five test materials Proteobacteria was the main bacterial phylum.

Biofilms formed within the acidic and the neutral biotrickling filters for treating H2S-containing waste gases

Microbial cell in the innermost biofilm have higher viability, and produce polysaccharide as the main component of EPS in acidic environment.