Electron Flow Rate in Microbiologically Influenced Corrosion and Its Applications

Microbiologically influenced corrosion (MIC) involves two types of microorganisms; one causes corrosion by directly consuming an electron from a metal, while the other produces corrosive substances, such as acids or sulfides, thereby indirectly inducing corrosion. In this chapter, the electron flow in the direct type of MIC and the possibility of its application is discussed, and the predicted mechanisms of such corrosion will also be described. Since an iron-corrosive methanogen produces methane and hydrogen during corrosion, and not any corrosive substances, the electron consumption can easily be estimated from gas production linked with energy conversion. Moreover, the adhesion of cells to the metal surface is essential, and notably, it accelerates the electron flow rate compared to abiotic chemical corrosion. Furthermore, when iron-corrosive methanogens are in the presence of sulfate-reducing bacteria (SRB), the electron flow rate is further accelerated; therefore, SRB play a role as enhancers. These findings suggest that electron-consuming methanogens could be useful for microbial electrosynthesis from renewable energy sources; therefore, the identification of truly corrosive microorganisms is crucial.