Metal corrosion induced by microbial activity – Mechanism and control options

Study of Anticorrosion and Antifouling Properties of a Cu-Doped TiO2 Coating Fabricated via Micro-Arc Oxidation

As a promising material for petroleum industrial applications, titanium (Ti) and its alloys receive wide attention due to their outstanding physicochemical properties. However, the harsh industrial environment requires an antifouling surface with a desired corrosion resistance for Ti and its alloys. In order to achieve the desired antifouling properties, micro-arc oxidation (MAO) was used to prepare a Cu-doped TiO2 coating. The microstructure of the Cu-doped TiO2 coating was investigated by TF-XRD, SEM, and other characterization techniques, and its antifouling and anticorrosion properties were also tested. The results show the effects of the incorporation of Cu (~1.73 wt.%) into TiO2 to form a Cu-doped TiO2, namely, a Ti-Cu coating. The porosity (~4.8%) and average pore size (~0.42 μm) of the Ti-Cu coating are smaller than the porosity (~5.6%) and average pore size (~0.66 μm) of Ti-blank coating. In addition, there is a significant reduction in the amount of SRB adhesion on the Ti-Cu coating compared to the Ti-blank coating under the same conditions, while there is little difference in corrosion resistance between the two coatings. There, the addition of copper helps to improve the fouling resistance of TiO2 coatings without compromising their corrosion resistance. Our work provides a practical method to improve the antifouling function of metallic Ti substrates, which could promote the application of Ti in the petroleum industry.

Biofilms and beyond: a comprehensive review of the impact of Sulphate Reducing Bacteria on steel corrosion

Sulphate-reducing bacteria (SRB) are known to cause severe corrosion of steel structures in various industries, resulting in significant economic and environmental consequences. This review paper critically examines the impact of SRB-induced corrosion on steel, including the formation of SRB biofilms, the effect on different types of steel, and the various models developed to investigate this phenomenon. The role of environmental factors in SRB-induced corrosion, molecular techniques for studying SRBs, and strategies for mitigating corrosion are discussed. Additionally, the sustainability implications of SRB-induced corrosion and the potential use of alternative materials were explored. By examining the current state of knowledge on this topic, this review aims to provide a comprehensive understanding of the impact of SRB-induced corrosion on steel and identify opportunities for further research and development.

Fluid-driven bacterial accumulation in proximity of laser-textured surfaces

In this work we investigated the role of fluid in the initial phase of bacterial adhesion on textured surfaces, focusing onto the approach of the bacterial cells towards the surface. In particular, stainless steel surfaces textured via femtosecond laser interaction have been considered. The method combined a simulation routine, based on the numerical solution of Navier-Stokes equations, and the use of a theoretical model, based on the Smoluchowski's equation. Results highlighted a slowdown of the fluid velocity field in correspondence of the surface dales. In addition, a shear induced accumulation on the top of the surface protrusions was predicted for motile bacterial species, E. coli. In particular, we observed a role of the surface protrusions in increasing the range over which motile bacterial species are attracted towards the surface through a rheotactic mechanism. In other words, we found that, in certain conditions of fluid flow and textured surface morphology, surface protrusions act as a sort of "rheotactic antennas".

The effect of high temperature aging on the corrosion resistance, mechanical property and antibacterial activity of Cu-2205 DSS

The effects of high temperature aging on the corrosion resistance, mechanical property and antibacterial activity of a copper-bearing 2205 duplex stainless steel (Cu-2205 DSS) were investigated. The results from scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and EDS analysis showed that after aging the proportion of γ phase in microstructure was increased and new σ phase and copper-rich precipitates were formed. The mechanical properties including hardness and tensile and yield strengths of the aged Cu-2205 DSS were significantly enhanced compared to the solution-treated Cu-2205 DSS as well as the 2205 DSS. Electrochemical measurements including electrochemical impedance spectroscopy, potentiodynamic polarization curves and potentiostatic polarization scan were performed to evaluate the corrosion behavior of the Cu-2205 DSS. It was found that aging increased the uniform corrosion resistance but had slightly adverse effect on the pitting corrosion resistance. Additionally, the antibacterial performance of aged Cu-2205 DSS was significantly improved compared to the solution treated Cu-2205 DSS, which was attributed to the more release of copper ions from the matrix that killed the bacteria cells and inhibited the biofilm formation on the surface. The above results suggest that Cu-2205 DSS after high temperature aging revealed good mechanical property, antibacterial performance, and corrosion resistance, which will further expand the application of duplex stainless steel in marine engineering fields.

Electrochemical and spectroelectrochemical characterization of bacteria and bacterial systems

Microbes, such as bacteria, can be described, at one level, as small, self-sustaining chemical factories. Based on the species, strain, and even the environment, bacteria can be useful, neutral or pathogenic to human life, so it is increasingly important that we be able to characterize them at the molecular level with chemical specificity and spatial and temporal resolution in order to understand their behavior. Bacterial metabolism involves a large number of internal and external electron transfer processes, so it is logical that electrochemical techniques have been employed to investigate these bacterial metabolites. In this mini-review, we focus on electrochemical and spectroelectrochemical methods that have been developed and used specifically to chemically characterize bacteria and their behavior. First, we discuss the latest mechanistic insights and current understanding of microbial electron transfer, including both direct and mediated electron transfer. Second, we summarize progress on approaches to spatiotemporal characterization of secreted factors, including both metabolites and signaling molecules, which can be used to discern how natural or external factors can alter metabolic states of bacterial cells and change either their individual or collective behavior. Finally, we address in situ methods of single-cell characterization, which can uncover how heterogeneity in cell behavior is reflected in the behavior and properties of collections of bacteria, e.g. bacterial communities. Recent advances in (spectro)electrochemical characterization of bacteria have yielded important new insights both at the ensemble and the single-entity levels, which are furthering our understanding of bacterial behavior. These insights, in turn, promise to benefit applications ranging from biosensors to the use of bacteria in bacteria-based bioenergy generation and storage.

Corrosion resistance and antibacterial activity of procyanidin B2 as a novel environment-friendly inhibitor for Q235 steel in 1 M HCl solution

Flavonoids, alkaloids, glucosides and tannins with good corrosion inhibition are the main natural components in plants. In this work, procyanidin B2 (PCB2), a natural flavonoid, was firstly isolated from Uncaria laevigata. Corrosion inhibition, chemical reactivity and adsorption of PCB2 on Q235 carbon steel were described by experimental and theoretical studies. The inhibition performance of PCB2 as a green corrosion inhibitor was evaluated by electrochemical and gravimetric tests. The binding active sites and activities thereof on the steel surface were illustrated by quantum chemistry, and the equilibrium configuration was predicted by molecular dynamics simulation. PCB2 exhibits good corrosion inhibition on Q235 steel over a wide temperature range. The electrochemical results show that PCB2 is a mixed inhibitor, and its inhibition efficiency increases with the addition of PCB2 concentration. Moreover, the protective film is formed on the steel and the active corrosion sites are blocked significantly by surface analysis. Additionally, the theoretical calculation proves a strong interaction between PCB2 molecule and carbon steel. Besides, the antimicrobial activity was also preliminarily studied. This suggests that PCB2 exhibits better antimicrobial activity against many Gram-positive and Gram-negative bacteria. As a novel green corrosion inhibitor and antimicrobial agent, PCB2 is worthy of further exploitation.