An Auger and depth profiling study of the sulfidation of iron and Fe-25 wt. % Cr alloy in H2S

Abstract

Polycrystalline iron and an Fe-25 wt. % Cr alloy were exposed from 200 to 300 °C in an H2S–argon mixture at one atmosphere pressure. Depth profiling was conducted on the sulfidized specimen in an Auger spectrometer. For both Fe and the Fe–Cr alloy temperature had a much stronger effect than exposure time on the growth rate of the sulfide layer. The sulfidation rate of the Fe–Cr alloy was much lower than that for pure iron. Evidence from the depth profile indicates that the growth of the sulfide layer below 250 °C proceeds primarily by the difffusion of iron rather than sulfur ions through the scale.