Pot-shaped Pitting Corrosion of SUS304 Welded Coupon Immersed in Natural Seawater and Microorganism Analysis

Abstract

Pot-shaped pitting corrosion occurred in SUS304 coupon with intact weld part immersed in natural seawater for 10 months. Removal of scale and roughness on weld part prevented severe corrosion for 10 months. Hypothetical corrosion progress mechanism by cooperative effect of iron oxidizing bacteria, Leptothrix sp., which might oxidize Fe²⁺ to Fe³⁺ and iron reducing bacteria, Shewanella sp., which might reduce Fe³⁺ to Fe²⁺ using electron directly obtained from metal by extracellular electron transfer （EET） was proposed.