XPS characterization of the oxide scale on fully processed non-oriented electrical steel sheet

An X-ray photoelectron spectroscopy analysis of the surface of fully processed, non-oriented, electrical steel sheet was performed in an attempt to elucidate the chemistry of the complex oxide scale. Ar+ sputtering was used to clean the surface contamination. Not only Fe2+, but also Fe0 states were detected in addition to the Fe3+ in the top several tens of nanometers of the 1–5-μm-thick complex oxide scales. This reduction of iron was explained as being due to the preferential sputtering of the oxygen atoms from the iron compounds in the Ar+ sputtering process. A fayalite reduction mechanism is proposed to account for the reduction of the iron down to Fe0. The results of the study indicate that X-ray photoelectron spectroscopy is limited to the determination of thick, complex oxides in multicomponent iron alloys.