Geobacter sulfurreducens: An iron reducing bacterium that can protect carbon steel against corrosion?

• The effect of an Fe-reducing bacterium on the corrosion of carbon steel was studied.
• G. sulfurreducens promoted the formation of an Fe(II) phosphate layer on the steel.
• The layer formed in presence of bacteria reduced the further corrosion of carbon steel.
• Corrosion protection was evidenced by coupling EIS, SEM and OCP observations.

The effect of Geobacter sulfurreducens on the electrochemical behaviour of carbon steel in anaerobic phosphate solution is studied here. In natural environments, G. sulfurreducens is able to reduce Fe(III) to Fe(II) during the oxidation of acetate. High availability of Fe(II) promoted the formation of an iron (II) phosphate layer on the steel. It is assumed that this phosphate layer, formed only when bacteria were present, is responsible for maintaining the corrosion potential stable even after intrusion of air. In contrast, the corrosion potential in the abiotic experiments suffered an increase of 450 mV after few hours of exposure to air.