Real-time electrochemical monitoring of the progress of sulfate reducing bacterially–induced corrosion of carbon steel

ABSTRACT Microbiologically influenced corrosion (MIC) is a widespread problem in the oil and gas industry, and sulfate reducing bacteria (SRB) cause the most aggressive kind of corrosion. A sulfate-reducing enrichmnent culture was obtained from a natural gas transmission line, and incubated in split chamber-zero resistance ammetry (SC-ZRA) incubations. Here, carbon steel electrodes were placed in a synthetic gas field brine in opposing chambers that were connected with a salt bridge. To mimic the heterogeneous metal coverage of a metal surface that causes MIC, one chamber was experimentally manipulated with addition of the SRB culture, while the other was uninoculated. Initial measurement of positive current between the electrodes in incubations with an organic electron donor (lactate) indicated a period of priming of the metal surface by planktonic SRB, before the current transitioned to negative, indicating that the cathodic corrosive reaction was occurring on the electrode exposed to SRB activities. This negative current is consistent with hypothesized mechanisms of SRB-induced corrosion, and was observed in lactate-free incubations and in uninoculated incubations amended with sulfide. These observations, combined with SRB metabolic patterns and mass loss analyses indicate the dynamic nature of SRB-mediated corrosion and illustrate the utility of real-time monitoring of MIC activities.