Microbial utilization of cathodic hydrogen and related corrosion

Microbial corrosion is the deterioration of a material by corrosion processes that occur directly or indirectly as a result of the activity of microorganisms. Although it is a widely recognized phenomenon in many industrial processes worldwide, the fundamental corrosion mechanisms are not understood, it is not well defined, and the microbial effect has not been quantified. The objective of this research was to show a relationship between cathodic hydrogen utilization by bacteria and corrosion at its onset for the purpose of improving its understanding and attempting to quantify the biological component of corrosion.; Two new experimental flowthrough and batch bioreactor systems were evaluated to reproduce anaerobic microbial corrosion. Both reactors were able to reproduce microbial corrosion in 24 hr. However, the batch system offered the better alternative to study microbial corrosion at an attractive economic operation. Since microbial corrosion is difficult to separate from pure electrochemical corrosion and electrochemical measurements offer a nondestructive technique to measure corrosion, the batch bioreactor was instrumented for electrochemical measurements and for physico-chemical analysis.; Results from potential-time curves, dissolved iron profiles, and differential corrosion currents indicated that metals were reactive to the presence of bacteria. However, the results were not adequate to quantify the biological component of corrosion. Significant increases in corrosion rates, observed during the addition of a terminal electron acceptor, suggested a catalytic effect on the bacterial hydrogenase system. The observation of cracks on steel samples suggested the occurrence of hydrogen embrittlement.; The results of this research are important because they offer a new approach for the investigation of microbial corrosion, the triad cell offers an opportunity to quantify the biological component of corrosion, and a new mechanism was proposed for the understanding of the onset of anaerobic microbial corrosion.