Corrosion of carbon steel by Pseudomonas stutzeri CQ-Z5 in simulated oilfield water

Carbon steel, an important infrastructure material in the petroleum industry, experiences serious damage due to Microbially Influenced Corrosion (MIC) with untold economic impact. Pseudomonas stutzeri CQ-Z5 with solid biofilm formation and organic acid-producing ability was isolated from Changqing oilfield produced water. The corrosion behavior and mechanism of 20^# carbon steel by P. stutzeri CQ-Z5 were explored in a simulated oilfield product water circulating device. Bacteria inoculation can hasten steel corrosion, the maximum corrosion rate reached 1.84 mm y⁻¹. Pitting corrosion on rust layer was observed using SEM, and CLSM monitored the change in biofilm thickness. XRD displayed that oxides were the primary corrosion products, including Fe₂O₃, Fe₃O_4, and FeOOH. Analysis of contributions of corrosion types indicated that biofilm corrosion contributes 72 % to total corrosion, far higher than those of ion erosion and organic acid decay. Many genes involved in iron metabolism, biofilm synthesis, and organic acid production were annotated in the genome of P. stutzeri CQ-Z5. Accordingly, a hypothetical corrosion mechanism model of P. stutzeri CQ-Z5 for carbon steel involvement of initial ion erosion, then biofilm corrosion and organic acid decay was proposed. The work helped prevent carbon steel corrosion and improve corrosion mitigation strategies.