Heterogeneous corrosion of mild steel under SRB-biofilm characterised by electrochemical mapping technique

Heterogeneous corrosion of mild steel under sulphate reducing bacteria (SRB)-biofilm was characterised by wire beam electrode (WBE) technique and electrochemical impedance spectrum. The potential/current distributions of the WBE under SRB-biofilm showed that the potential maps could not indicate the localised corrosion of steels beneath biofilm due to the fact that all wire electrodes were short-circuited by the highly conductive sulphide precipitates embedded in SRB-biofilm. Instead, the galvanic current maps may give a good indication. The characteristic of super-capacitance (0.21 F/cm2) of SRB-biofilm was attributed to the huge specific surface area of conductive pore walls inside biofilm.

► Highly conductive SRB-biofilm can shield the potential differences of mild steel. ► Potential maps fail to indicate the localised corrosion of steel under SRB-biofilm. ► Galvanic current maps can detect the location of localised corrosion under biofilm. ► SRB-biofilm is super-capacitive due to the conductive sulphide micropores.