304L stainless steel oxidation in carbon dioxide: An XPS study

From the early beginning of the oxidation of 304L stainless steel in carbon dioxide at 1273 K (1 min, for a weight gain of 0.02 mg cm−2), the surface of the alloy was entirely covered by oxides: magnetite Fe3O4, chromia Cr2O3 and traces of wüstite Fe1−xO. Later on, for weight gains approaching 1 mg cm−2, magnetite remained at the outer interface, with traces of hematite (Fe2O3), above a thick layer of wüstite Fe1−xO. Magnetite and wüstite may favour adhesion of thermal plasma protective coatings such as alumina.

Research highlights▶ During 304L oxidation in CO2, the outer oxide contains always magnetite. ▶ Maybe this result (Fe3O4 on surface) could be generalized to other iron-based alloys. ▶ The presence of Fe3O4 is very favourable in view of alumina coatings on 304L steel.