Electrochemical Detection of Carbon Steel Corrosion Induced by Fermentative Bacteria From Natural Gas Transmission Lines

The metabolic potential and corrosive activities of a fermentative bacterial enrichment culture from a natural gas transmission line were characterised. Three metagenome-assembled genomes (MAGs) attributable to Cytobacillus, Lacrimispora and Staphylococcus spp. were obtained. These MAGs hosted genes involved in the fermentation of carbohydrates to organic acids, which was reflected in the acidification of the growth medium by the culture. To evaluate the corrosive activities of the culture, it was incubated in a split chamber-zero resistance ammetry (SC-ZRA) format. This involved deploying carbon steel coupons immersed in liquid medium in opposing chambers of an electrochemical cell. Measurement of current between the coupons indicated the extent and mechanism of corrosion. When the enrichment culture was added to one side of an SC-ZRA incubation with bicarbonate-buffered medium, pH change and corrosion were minimal. In bicarbonate-free medium, the culture acidified the medium, induced electron transfer from the uninoculated chamber to the inoculated chamber, and caused mass loss. These results indicate that fermenter-induced microbially influenced corrosion (MIC) is due to localised fluid acidification, inducing anodic reactions on the metal surface exposed to the microorganisms and mass loss of the non-exposed metal.