Evolution of Scale Microstructure and the Pressure Dependence of the Sulfidation Rate of Iron

The sulfidation rate of iron to has been measured, and the microstructural features of this sulfide have been carefully studied. The measurements were made at 700°C in pure sulfur vapor covering the pressure range from 1–10 3 Pa; 700°C is a temperature in the midrange of previous measurements, and was selected to facilitate a study of the general aspects of the microstructure and growth rate of this highly nonstoichiometric sulfide of iron. We find that the growth direction and microstructure of the scale are pressure dependent, and contrary to previously reported results, we find no evidence to suggest that the growth rate of iron sulfide is any different in pure sulfur vapor than in mixtures.