Pitting and Crevice Corrosion Behaviors of 2507 Duplex Stainless Steel in Deep Water Environment of the South China Sea

The pitting and crevice corrosion behaviors of 2507 duplex stainless steel in deep water environment of South China Sea were studied through bacterial culture test and actual sea immersion corrosion test. Electrochemical characteristics and micro corrosion morphology of the duplex stainless steel were analyzed by electrochemical test, optical microscope, scanning electron microscope and energy dispersive spectrometer. The results showed that there were no sulfate-reducing bacterias (SRB) and manganese-oxidizing bacterias (MOB) flora in deep water of the South China Sea, and there were about 400 iron-oxidizing bacterias (IOB) in 1L of deep water of the South China Sea. After immersion in the South China Sea deep water environment for 17 d, the 2507 duplex stainless steel began to show a tendency of pitting corrosion, this might be related to the attachment of microorganisms and the enrichment of chloride ions. After immersion for 120 d and 592 d, the surface of 2507 duplex stainless steel had pits, and with the extension of immersion time, the depth of pits did not increase significantly. After immersion for 506 d and 592 d, corrosion pit with the depth about 7 μm appearred in the 2507 duplex stainless steel crevice area.