Multi-mode scanning electrochemical microscopic study of microbiologically influenced corrosion mechanism of 304 stainless steel by thermoacidophilic archaea

•Multiple modes of SECM were used to study MIC mechanism.•Change of biofilm morphology was monitored by the negative feedback mode of SECM.•Corrosion electrochemical signal was presented by the redox competition mode of SECM.•Fe2+ oxidation metabolism of M.cuprina was studied by SECM.•The role of Fe2+ oxidation metabolism of M.cuprina in MIC was clarified. In this work, different modes of scanning electrochemical microscopy (SECM) were employed to study the biofilm morphology, oxygen concentration distribution and Fe2+ oxidation metabolism during the microbiologically influenced corrosion (MIC) of 304 stainless steel caused by the thermoacidophilic archaeon Metallosphaera cuprina. The results of in situ SECM study suggested that the decrease in the concentration of organic nutrients forced the M. cuprina biofilms to use Fe2+ as an electron donor and consume more Fe2+ from the pitting corrosion, which accelerated anodic dissolution and led to aggravated pitting corrosion of stainless steel.