AN XPS STUDY OF ANODIC OXIDE FILM ON 1Cr18Ni9 STAINLESS STEEL

The XPS has been used to study the composition and structure of the oxide film on stainless steel. The film was formed in the transpassive region during the anodic polarization in H_2SO_4 and after a treatment with Na_2MoO_4. It has been found that the ratio of Cr to Fe in the film is about three times higher than that in the bulk. The analysis of the valence states showed that the distribution of each constituent in the film is not uniform. The film has a three-layer structure.The outer layer is rich in OH~- and the middle layer consists mainly of Cr_2O_3 and Fe_2O_3, while the rest of the layer up to the interface contains the Fe~(2+) and Fe~0. The Mo ions have been found throughout the film. The possible mechanism for passivation of the anodic polarization in the transpassive region was discussed and a comparison was made with other oxide films.