Microbiologically influenced corrosion of steel in coastal surface seawater contaminated by crude oil

Abstract Petroleum-hydrocarbons spilt in surface seawater may pose potential threats to the corrosion of steel infrastructures. We show that crude oil accelerated steel corrosion mainly by accelerating microbiologically influenced corrosion (MIC). Crude oil led to the dominance of marine oil-degraders including Alcanivorax and Marinobacter in both seawater and steel rust, rather than sulfate-reducing bacteria (SRB) which dominated the rust microbial community in the no-oil group. Crude oil not only enhanced microbial oxygen respiration and aerobic hydrocarbon degradation but also nitrate reduction and anaerobic hydrocarbon degradation process in steel rust, indicating more heterogeneous microenvironments formed on steel surfaces. Furthermore, the low abundance of SRB and dissimilatory sulfate reduction gene ( dsr ), and the existence of iron-carbonate and iron-sulfate minerals implied that microbial sulfide, previously regarded as the main cause of MIC, was not the major contributor to steel corrosion in early petroleum-polluted seawater. Marine specialized oil-degraders seem to play more significant roles under such conditions.