Influencing passivity breakdown resistance of ultra-thin oxides on alloy surfaces through photo-excitation

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. In this presentation, we will discuss our results on passive oxide growth on Al, Ni, Al-Ni alloys and how the corrosion resistant properties of the native oxide films can be significantly enhanced by photo-excitation. We will present results on spatially resolved current mapping across ultra-thin passive oxides using scanning probes, X-ray photoelectron spectroscopy and polarization measurements on the various oxide films. The role of compositional control in affecting passivity breakdown of ultra-thin oxides will be discussed in detail