Anticorrosive influence of Acetobacter aceti biofilms on carbon steel

Enhanced corrosion of 2205 duplex stainless steel by Acetobacter aceti through synergistic electron transfer and organic acids acceleration

Acetobacter aceti is a microbe that produces corrosive organic acids, causing severe corrosion of industrial equipment. Previous studies have focused on the organic acid corrosion of A. aceti, but neglected the possibility that it has electron transfer corrosion. This study found that electron transfer and organic acids can synergistically promote the corrosion of 2205 duplex stainless steel (DSS). Electrochemical measurement results showed that corrosion of 2205 DSS was more severe in the presence of A. aceti. Surface analysis indicated a thick biofilm formed on the steel surface, with low pH and dissolved oxygen concentrations under the biofilm. Corrosion intensified when A. aceti lacked a carbon source, suggesting that A. aceti can corrode metals by using metallic substrates as electron donors, in addition to its acidic by-products.

Investigation of biochemical, enzymatic, and metagenomic profiles of garbage enzymes and its application in dumping site leachate treatment

The current article focuses on the preparation and characterization of garbage enzyme (GE) and explores its applications in treating leachate. GE is prepared from fruit and vegetable wastes and characterized via analysis of metabolites, carbohydrates, proteins, antioxidants, and enzymatic activities. This study extends our understanding of GE by reporting the presence of various metabolites. Moreover, a metagenomic analysis of GE is presented, shedding light on the microbial diversity. Firmicutes emerged as the dominant phylum, surpassing other phyla, including Proteobacteria and Actinobacteria. When exploring the potential for leachate treatment, the results indicate that vegetable GE shows 68% reduction in COD (chemical oxygen demand) and 39% reduction in ammoniacal nitrogen. Similarly, non-citrus GE also showed 64% reduction in COD and a 37% reduction in ammoniacal nitrogen, followed by citrus GE with a 33% reduction in COD and a 34% reduction in ammoniacal nitrogen compared to the control.

Influence of Bacillus safensis and Bacillus pumilus on the electrochemical behavior of 2024-T3 aluminum alloy

In this work, electrochemical techniques were employed to evaluate the contribution to the corrosion and corrosion inhibition of 2024-T3 aluminum alloy by two Gram-positive bacteria. In addition, polarized impedance was used to determine the microbial effect on the cathodic and anodic reactions. These microorganisms were collected from a tropical environment due to the favorable bacterial growth of this kind of climate. The alloy was exposed to the sterile medium and inoculated for up to 12 days evaluating the microbiological and electrochemical behavior. The results by linear scanning voltammetry showed that the B. safensis and B. pumilus caused a dual effect of increase and decrease currents, and through electrochemical impedance spectroscopy, showed in some cases, inductive loop, which could be associated with local corrosion and another case, an increasing impedance could be related to protection. In addition, a morphological characterization was performed by scanning electron microscopy before and after exposure, showing an increase in copper precipitation in the vicinity of the intermetallic phases by bacteria, attributed to local corrosion, but, in general, a significant effect of damages was not observed.

Role of 2-mercaptopyridine on control of microbial influenced corrosion of copper CW024A metal in cooling water system

In this present study, the biocorrosion behaviour of Bacillus thuringiensis EN2 and B. oleronius EN9 on copper metal CW024A (Cu) in cooling water system (1% chloride) were evaluated using weight loss, electrochemical impedance spectroscopy (EIS) and surface analysis. In presence of EN2 and EN9, the corrosion rates (CR) were higher, about 0.021 mm/y and 0.032 mm/y than control system (0.004 mm/y). On the other hand, the presence of corrosion inhibitor 2-mercaptopyridine (2-MCP) with bacteria (EN2 and EN9), the biofilm on metal surface was highly inhibited and thus reduces the corrosion rate (CR: 0.004 mm/y). The electrochemical behaviour of CW024A metal was correlated with the adsorbed corrosion inhibitor film and biofilm. Atomic force microscopy (AFM) analysis revealed that the presence of EN2 and EN9 more pits was observed on the metal surface rather than 2-MCP system. EIS confirms the inhibitor act as cathodic type of inhibitor and thus leads to the inhibition of CR. Overall, this work concluded that corrosion inhibitor (2-MCP) inhibits, the bacterial biofilm formation on the metal surface due to the formation of productive layer on metal surface as coordination of NH bond. Which leads to the reduction of bacterial attachment and thus higher corrosion inhibition efficiency (75%) obtained. This is the first work disclosing the role of 2-MCP formulations as potent anti-bacterial and corrosion inhibition efficiency on copper metal in cooling water tower environment.