Crevice corrosion resistance and structure of passive film on Fe-Mn-Si-Cr-Ni Steel

Abstract

The crevice corrosion resistance of an Fe-Mn-Si-Cr-Ni (15 Mn) steel as a shape memory alloy was estimated by laser microscopy and statistical calculation of the corrosion depth, and the structure of the passive film formed on the steel was examined by EELS (Electron Energy Loss Spectroscopy) analysis using TEM (transmission electron microscopy). The crevice corrosion results were analyzed using a Gumbel distribution, and the mode (λ) and distribution parameter (α) of the maximum corrosion depth of the 15 Mn steel were found to be much smaller than those of 430 stainless steel (SUS: 16Cr - Fe). This shows that 15 Mn steel has a higher crevice corrosion resistance than 430 SUS steel. In AES and XPS analysis, the passive film of 15 Mn steel was shown to contain Fe, Mn, Cr, Si and Ni. From TEM-EELS, the passive film was found to consist of 2 layers. In the passive film, Cr and Si are thought to be effective early, with Ni preventing penetration of crevice corrosion. It was found that 15 Mn steel could maintain a passive film which was composed of effective elements in a crevice corrosion environment.