Mechanism of Anaerobic Microbial Corrosion Suppression by Mild Negative Cathodic Polarization on Carbon Steel

Microbially influenced corrosion (MIC) in anaerobic environments has serious negative impacts on the industry and economy. While cathodic polarization (CP) has been widely used to inhibit abiotic corrosion, its potential applicability on MIC has been scarcely elucidated. Here, we report high MIC suppression by CP and its potential mechanism on a carbon steel electrode with Desulfovibrio vulgaris Hildenborough, a model sulfate-reducing bacterium for MIC. Following MIC associated with FeS2 formation on carbon steel, we initiated CP at -0.5 V (vs the standard hydrogen electrode) for 12 h, which consumed low electricity but resulted in a >80% reduction in the corrosion current for at least 1 week. X-ray photoelectron spectroscopy and transcriptome analyses showed the reduction of FeS2 to FeS and downregulated cell metabolism, respectively, thus suggesting that HS-, produced via the electrochemical reduction of FeS2, deactivated D. vulgaris at -0.5 V. Accordingly, a weaker impact was observed at positive potentials of -0.3 and -0.4 V that scarcely reduced FeS2, and at negative potentials of -0.6 and -0.7 V that reduced FeS2, but produced hydrogen that promotes the growth of D. vulgaris. This potential mechanism suggests the broad applicability of mild negative CP to suppress MIC in an environmentally friendly and cost-effective manner.