Microbial corrosion of high manganese austenitic steel by a sulfate reducing bacterium dominated by extracellular electron transfer and intergranular effect

Microbiologically influenced corrosion (MIC) of high manganese steel (25Mn) by a marine sulfate reducing bacterium (SRB) was systematically investigated. Mn² + enhanced SRB activity by H ₂ S detoxification. The culture medium with low carbon source increased MIC by 2.1 times. 4 % Cr in 25Mn provided partial passivation . Riboflavin and nano-magnetite injections validated the dominant contribution of extracellular electron transfer mechanisms. Electron backscatter diffraction showed the intergranular corrosion at austenite boundaries. SRB enhanced hydrogen permeation and decreased tensile strength by 21 %. This study identifies the primary mechanism of 25Mn and provides important insights into material design and corrosion mitigation. • High manganese steel (25Mn) MIC by SRB involves uniform and localized corrosion. • Mn 2+ enhances SRB planktonic and sessile growth due to H 2 S detoxification. • Extracellular electron transfer (EET) is the main MIC mechanism. • Carbon source starvation and injections of EET promoters accelerate MIC. • SRB biofilm triggers intergranular corrosion of 25Mn.