A Photocurrent Spectroscopic Investigation of Passive Films on Ferritic Stainless Steels

Abstract

An investigation of the surface films on three different ferritic stainless steels was carried out by means of photocurrent spectroscopy. All the specimens showed detectable photoeffects only after long anodic polarization times in chloride ion‐containing solution. The passive films showed n‐type behavior and bandgap values dependent upon the applied potential. A difference was observed in the bandgap values of films grown on different alloys. The photoelectrochemical behavior of the films is compared to that of passive layers on pure iron and chromium. Due to the lack of photoelectrochemical data on passive films on Cr a preliminary investigation on this metal has been also carried out. The experimental results are interpreted in terms of formation of different iron‐chromium oxide solid solutions.