Valence band x-ray photoelectron spectroscopic investigation of surface cleanliness of aluminum metal and its alloys

Aluminum and its alloys are used in many practical situations. The surface preparation and treatment of these materials can significantly impact their practical applications. This article presents valence band and core x-ray photoelectron spectroscopy (XPS) data on these materials, showing in particular how the valence band region can provide an indication of differences in surface composition unobtainable in the core XPS region, or by other surface analytical probes. Surface chemistry is often vital to certain industrial applications. In this article the surface chemistry of stearate based lubricants is discussed, and the changes in the surface chemistry that results when these lubricants are applied to aluminum metal and alloy surfaces is discussed. It is possible to interpret the valence band region by comparison with spectra calculated from molecular orbital calculations, and it can be seen that stearic acid and stearates have a very characteristic valence band. The lubricants can be seen to tenaciously hold onto the surface of metal and alloys after application.