Accelerated cathodic reaction in microbial corrosion of iron due to direct electron uptake by sulfate-reducing bacteria

Microbially influenced iron corrosion by sulfate-reducing bacteria (SRB) is conventionally attributed to the chemical corrosiveness of H2S, facilitated abiotic H+-eduction at deposited FeS, and biological consumption of chemically formed ('cathodic') H-2. However, recent studies with corrosive SRB indicated direct consumption of iron-derived electrons rather than of H-2 as a crucial mechanism. Here, we conducted potentiodynamic measurements with iron electrodes colonized by corrosive SRB. They significantly stimulated the cathodic reaction, while non-corrosive yet H-2-consuming control SRB had no effect. Inactivation of the colonizing bacteria significantly reduced current stimulation, thus confirming biological catalysis rather than an abiotic cathodic effect of FeS. (c) 2012 Elsevier Ltd. All rights reserved.