Indication of chromium oxide hydroxide evaporation during oxidation of 304L at 873 K in the presence of 10% water vapor

The oxidation of type 304L stainless steel was investigated at 873 K in the presence of O-2 and O-2+10% H2O. Oxidation time varied between 1 and 672 hr. The oxidized samples were investigated by a number of surface-analytical techniques including grazing-angle XRD, SEM/EDX, auger spectroscopy, SIMS and XPS. Oxidation in dry oxygen results in the formation a corundum-type oxide (Me2O3) with additional formation of spinel oxides after prolonged exposure. The oxide layer contained mainly chromium, with smaller amounts of Fe and Mn. Oxidation in the presence of water vapor results in an oxide that contains more Fe and less Cr, the outer part of the oxide being depleted in Cr. In the presence of water vapor, a mass loss is detected after prolonged exposure. We show that the mass loss is caused by chromium evaporation. The volatile species is suggested to be CrO2(OH)(2).