Studies on passive oxide films on aluminum and aluminum-alloys: Stoichiometry, electrochemical properties and photon effects.

摘要

The ability to exercise atomic level control over the structure and chemical composition of surface oxides formed on metal alloys is crucial towards understanding their corrosion resistance in various aqueous media. This is complicated by the fact that the kinetics of oxidation is vastly different for metals such as Al, Ni, Cu etc that make up constituents of alloys. We explore the use of photo-excitation to influence oxidation rates of different metals in an athermal manner and how this can be used in an elegant manner to control the composition and structure of ultra-thin (1--3nm) oxide films formed on alloy surfaces. Using high resolution XPS, NRA and EIS measurements, we explore the effects of photon-excitation on passive oxide growth on Al, Ni, Cu, Al-Ni, Al-Cu, and Al-Cu-Ni alloys and how it relates to the enhanced corrosion resistant properties of the native oxide films. The role of compositional control in affecting passivity breakdown of ultra-thin oxides is studied in detail.