Anaerobic extracellular corrosion of steel
Materials Science and Engineering
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Few studies have been conducted on the influence of secreted molecules and metabolic by-products of obligate anaerobes on corrosion of steel. Although several anaerobes may be associated with corrosion, most studies have focused on sulfate reducing bacteria such as Desulfovibrio species and their innate role in anaerobic corrosion. While the phenomenon of occurrence of direct electron transfer between hydrogenases and electrode materials has been widely demonstrated in the field of bioelectrochemistry, either for the electrochemical oxidation of hydrogen, or for the electrochemical reduction of proton, such studies for corrosion are limited. Anaerobic corrosion caused by members of obligate anaerobe genus Clostridium was investigated. It was determined that the metal sample experiences a higher corrosion rate than could be attributed to free H2 or other metabolic products. An alternate hypothesis is proposed here. Corrosion rates were measured against various controls. The extent and efficiency of corrosion has also been examined in the presence of either an artificial electron shuttle viz. AQDS (anthraquinone-2,6-disulfonate). Samples were exposed to culture and iron concentration was monitored using Ferrozine method and surface analysis was conducted. We also hypothesize that consumption of molecular hydrogen, which is an end-product, does not significantly modify the corrosion rates. Experiments involving membranes were carried out to prove the presence of protein. Electrochemical experiments were also performed to show the redox properties of the protein. Corrosion products were identified using surface analytical techniques.