Microbially induced corrosion (MIC) of oil and gas transporation pipelines causes billions of dollars of damage and is difficult to detect over long spans of pipelines. Zero resistance ammetry (ZRA), whereby current induced between the two electrodes due to microbial corrosion is measured as an indicator of corrosive microbial activities, in pipelines could serve as an approach to real-time monitoring of MIC. To examine the electrochemical “signatures” of microbiological activities that could induce steel corrosion, we first used natural gas pipeline sludge as an inoculum for sulfate-reducing and fermentative bacterial enrichment cultures that predominantly contained Clostridia sp. and Desulfovibrio sp., respectively. We then incubated the cultures in split-chamber ZRA (SC-ZRA) incubations, where steel coupons were immersed in synthetic oil field brine in separate chambers (refered to as WE1 and WE2) that were electrochemically connected by a salt bridge. In this setting, we can mimic the conditions that could lead to MIC by inoculating the WE1 chamber with our enrichment cultures. Neither current between coupons nor mass loss (indicating corrosion) were observed when SC-ZRA incubations were not inoculated. While minimal current was observed in incubations with the fermentative enrichment, we observed current associated with sulfate reducing activities that indicated WE2 (in the ininoculated chamber) was serving as the anode, while WE1 was serving as the cathode. Indeed, greater mass loss from the WE2 coupon was greater than that of WE1, which is consistent with the anodic reaction, Fe0 ---&gt; Fe2+ + e-, occurring on WE2. These results suggest that differing microbial metabolisms give rise to differing electrochemical patterns and indicate when MIC is occurring, and can differentiate between the presence of non-corrosive microorganisms and the activities of corrosion-causing organisms.

Electrochemical identification of corrosive microbial activities in natural gas transmission lines

ACS Spring Meeting 2021

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