Inhibition of initial surface oxidation by strongly bound hydroxyl species and Cr segregation: H2O and O2 adsorption on Fe-17Cr

The initial stages of surface oxidation of Fe-17Cr (ferritic stainless steel) were investigated at 323 K by X-ray photoelectron spectroscopy (XPS) and inelastic electron background analysis. The results indicated the formation of a mixed iron-chromium oxide layer upon O2 exposure and the formation of a thin chromium oxyhydroxide layer upon H2O exposure. The oxidation of Fe did not occur in the latter case. Moreover, it was found that pre-exposing the Fe-17Cr surface to H2O significantly hinders subsequent oxidation by O2, thus providing a way to control the formation of nanoscale oxides on stainless steel materials. It was concluded that the formation of strongly bound hydroxyl species together with adsorbate-induced segregation of Cr severely limits the reaction between O2/H2O and Fe from the alloy.