A combined ISS and XPS investigation of passive film formation on Fe53Ni

Abstract

Abstract A surface analytical study of the Fe53Ni alloy passivation process in alkaline solution was carried out by ISS (ion scattering spectroscopy) and XPS (x‐ray photoelectron spectroscopy). The ISS depth profiles of the passive films formed in 1 M NaOH show an iron‐enriched outer part of the film that is about three monolayers thick and stays on the surface independently of the polarization potential. This finding may be related to the outer hydroxide Fe/Ni film identified by XPS. The inner part of the quasi‐steady‐state passive film is nickel enriched and its thickness grows linearly with the potential. The results obtained by ISS satisfactorily agree with those obtained on the same samples by XPS, which demonstrates that ISS can be used profitably as a semiquantitative tool for the investigation of thin surface layers; in addition, it provides a higher depth resolution than XPS.