Mechanistic investigation of ferric ion and ferriferous oxide on M. barkeri-mediated copper corrosion

Methanosarcina barkeri (M. barkeri) can cause microbiologically influenced corrosion (MIC) of copper in heat exchangers, where ferric ion (Fe³⁺) and ferriferous oxide (Fe₃O₄) also exist due to the corrosion of iron pipes with flowing water. It is worth noting that M. barkeri can reduce Fe³⁺ to Fe²⁺ or Fe, which may exhibit an unknown effect on copper corrosion. In this study, the molecular mechanism of copper corrosion by M. barkeri with Fe³⁺ and Fe₃O₄ was explored. In the presence of Fe³⁺, the corrosion was enhanced by 82.5 %, and M. barkeri and Fe³⁺ exhibited a synergistic effect on copper corrosion. It is attributed to that Fe³⁺ oxidized the copper and promoted the growth of M. barkeri and biofilm formation, thus promoting corrosion. Moreover, the corrosion by M. barkeri with Fe₃O₄ increased by only 27.7 %, and M. barkeri and Fe₃O₄ exhibited an antagonistic effect on the corrosion. Fe₃O₄ covered the coupon surface, which reduced the contact between the cells and the coupon, and thus inhibited electrochemical corrosion. This study provides new insights for methanogens-induced MIC, and also has far-reaching implication for the mitigation of MIC in heat exchangers.