Oxidation of AISI 304L stainless steel surface with atomic oxygen

Oxidation of stainless steel surface in oxygen atmosphere was investigated by Auger electron spectroscopy (AES) depth profiling. The samples made of AISI 304L stainless steel were exposed to highly non-equilibrium oxygen atmosphere at different temperatures between 300 and 800 K and for different periods between 5 and 600 s. The degree of dissociation of oxygen molecules was of the order of 10%. A thin oxide layer formed on the stainless steel surface consisted of the iron oxide. The thickness depended on the sample temperature. At room temperature it was 7 nm, and it remained the same up to 200 °C. With further increase of temperature, the thickness of the oxide layer increased and reached 40 nm at 450 °C. The thickness was independent of exposure time. The results were explained by two mechanisms of oxide growth. Up to 200 °C the oxidation was run by electro-migration, while at higher temperatures the thermal induced migration prevailed.