Abstract
Oxidation and corrosion studies of UHV-deposited Fe1-xPdx; (x = 0.07-0.66) films were carried out using Auger electron spectroscopy, x-ray photo-electron spectroscopy, atmospheric and electrochemical corrosion measurements, and scanning transmission electron microscopy. The Pd concentration required for passive alloys was found to depend on a variety of metallurgical factors including film deposition temperature and thickness and the extent of surface oxidation following film preparation. For example, the critical Pd concentration needed to obtain noble metal surface characteristics decreases from ~25 to ~6 atom percent on the film as the film deposition temperature is raised from 60° to 350°C. Extensive AES and XPS data show that Fe preferentially oxidizes to Fe2O3 at the air-oxide interlace for films oxidized at moderate (160°-225°C) temperatures, leaving a localized Pd-enriched region underneath the oxide layer. This localized Pd enrichment is attributed to a relatively slow interdiffusion of Pd and Fe at these oxidation temperatures. The corrosion resistance of lower Pd concentration films can be significantly improved by such preoxidation treatments. This finding is interpreted in terms of the formation of a dense, protective Fe2O3 layer and the presence of a thickened Pd-enriched region underneath the iron oxide layer. © 1979, The Electrochemical Society, Inc. All rights reserved.