Electrochemical characterization of aluminum alloy AA2024 − T3 influenced by bacteria from Antarctica

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.

Study of an Antarctic thermophilic consortium and its influence on the electrochemical behavior of aluminum alloy 7075-T6

Common alloys used for the manufacture of aircrafts are subject to different forms of environmental deterioration. A major one is corrosion, and there is a strong body of evidence suggesting that environmental microorganisms initiate and accelerate it. The development of an appropriate strategy to reduce this process depends on the knowledge concerning the factors involved in corrosion. In this work, a biofilm forming bacterial consortium was extracted in situ from the corrosion products formed in an aircraft exposed to Antarctic media. Two thermophilic bacteria, an Anoxybacillus and a Staphylococcus strain, were successfully isolated from this consortium. Two extracellular enzymes previously speculated to participate in corrosion, catalase and peroxidase, were detected in the extracellular fraction of the consortium. Additionally, we assessed the individual contribution of those thermophilic microorganisms on the corrosion process of 7075-T6 aluminum alloy, which is widely used in aeronautical industry, through electrochemical methods and surface analysis techniques.