Corrosion Consequences of Secondary Oxidation of Microbial Corrosion

Microbial corrosion scenarios based on the action of sulfate-reducing bacteria (SRB) under disbonded tape coatings on the outside of gas pipelines have been described previously. Secondary oxidation of these sites leads to formation of unique corrosion products. These have been associated with serious corrosion damage in the field. Laboratory studies were performed under simulated field conditions on an iron sulfide-steel (FeSx-Fe) galvanic corrosion cell sustained by anaerobic microbial activity. The effects of transitions from anaerobic to aerobic conditions on corrosion rates were documented. Results were correlated with field observations, and potential mechanisms were discussed.