Microbiologically influenced corrosion of oil-water pipeline steel from local field failure case to specific Shewanella & Desulfovibrio corrosion highlights the significance of hydrocarbon-degrading bacteria.

Unconventional natural gas pipeline corrosion is associated with microbes, especially sulfate-reducing bacteria (SRB), though it is uncertain if SRB's role is overemphasized. Using metagenomics, corrosion immersion, and microbial cultivation, diverse hydrocarbon-degrading microorganisms, such as Shewanella, in corroded pipeline rust layers, oil-water mixtures, and produced water from unconventional natural gas fields are identified. These bacteria use crude oil as a carbon source, accelerating pitting corrosion of carbon steel and forming corrosion product films (Pitmax = 28.96 μm). The 16S rRNA sequencing results show that Shewanella, prevalent in various steel service environments, is a potential key microorganism in pipeline corrosion. X70 steel exhibits lower electron transfer resistance than Desulfovibrio in the Shewanella medium. Shewanella's aerobic respiration degrades crude oil and oxidizes iron, speeding up iron oxide formation and magnesium phosphate precipitation. Microbial acidification of the oil-water medium also contributes to severe pitting corrosion beneath the oil film. Crude oil accelerates microbial growth. Thus, studying carbon steel corrosion in oil-water environments must consider the impact of hydrocarbon-degrading microorganisms.