Long-term field exposure corrosion behavior investigation of 316L stainless steel in the deep sea environment

The long-term deep sea corrosion behavior of 316L stainless steel was investigated through the field exposure corrosion experiments at 1200-3000m depths. Differing from the results of simulated tests and shallow sea field exposure, XPS analysis showed a result of only trivalent irons containing oxides and hydroxides instead of coexistence of bi- and tri-valent irons. With the sea depth increasing, corrosion potentials and pitting potentials shift negatively, and the data of 3000 m depth are -0.240 V (vs. SCE) and 0.201 V (vs. SCE), respectively, revealing the corrosion status is deteriorated. Corrosion behavior analysis showed that the corrosion weight loss of 316L is mainly attributed to crevice corrosion and pitting corrosion, and that the highest corrosion rate is 0.96 Inn y(-1) accompanying with a biggest pitting depth of 18.4 pm after one year exposing. The corrosion rate obtained from 3000 m deep sea is 3.2 times as much as that obtained from the shallow-sea environment.