A Study of the Structure and the Morphology of Oxide Films on Amorphous Al‐Fe‐Ce Alloys by XPS and SEM

Abstract

Aluminum‐based metallic glasses are of technological importance due to their high strength, low density, and anticipated high resistance to corrosion. We report on the corrosion characteristics of melt‐spun ribbons of . The amorphous alloys showed excellent corrosion properties in aqueous . We have also examined the composition, structure, and morphology of the native and passive oxide films using scanning electron microscopy (SEM), x‐ray photoelectron spectroscopy (XPS), and angle‐resolved XPS. We show that the composition of the native oxide film is that of . The thickness of the native oxide is estimated from angle‐resolved XPS data to be about 1.6 to 3.1 nm (i.e., nanometer). Passive films were formed in 0.9 weight percent (0.15M) solution by potentiostating below the pitting potential for 30 and 60 min. The passive oxide films contain oxidized Al, Fe, and Ce. The chemistry of Al in the passive oxide films is also that of . Iron appears to be present in the passive film as and and/or with varying mole fractions depending on alloy composition. Cerium in the passive film appears to be present in the +3 oxidation state as or . A small fraction of Ce in the passive film of is present in the +4 oxidation states as .