Effect of hydrogen on passive film and corrosion behaviour of 2507 super duplex stainless steel in H2S environment based on ToF-SIMS characterization

摘要

The effect of hydrogen on passive film and corrosion behaviour of 2507 super duplex stainless steel (SDSS) in H 2S environment was studied by electrochemical experiments and ToF -SIMS characterization. The results showed that sulfides were present in the passive film in the forms of FeSx and NiSx, and they were enriched in local passive film of the austenite phase since austenite was rich in Fe and Ni elements. In H2S-containing environments, the passive films had a bilayer structure. The inner layer was compose d of oxides of Cr and Ni, while the outer layer was enriched in oxides of Fe and Mo, hydroxides and sulfides. Moreover,hydrogen thickened the passive film, and induced the formation of hydroxides and sulfides in the passive film, which resulting in the dec rease in pitting resistance. Due to the better corrosion resistance of the austenite phase, pitting occurred at the ferrite phase and phase boundary.