Surface chemical studies of practical aluminum systems

This dissertation reports a study into the surface chemistry of practical aluminum systems. Aluminum itself is not a practically useful metal, however when it is alloyed with other metals such as magnesium and silicon, the resulting alloys are often ideal construction materials as they are strong, light weight and are naturally corrosion resistant due to a thin layer of oxidized aluminum. However many factors can play a part in the use of such alloys and surface chemistry is an overlooked factor despite having a major role in certain applications.; This study has been aimed at trying to detail the role surface chemistry plays in the use of aluminum alloys with particular emphasis on understanding how the surface chemistry can change during typical manufacturing processes and impact the final product. Specifically this study looks at two major areas of interest, firstly that of surface contamination and secondly that of surface film formation.; Depending upon the final use of the alloy, surface contamination of hydrocarbonaceous materials can be particularly undesirable. Thus it is important to be able to both identify possible contaminants and assess the degree of interaction between them and the surface. It has been found that by using direct sample biasing x-ray photoelectron spectroscopy hydrocarbonaceous surface contaminants can be "separated" and identified based on their electrical conductivities. Also, valence band photoelectron spectroscopy has been used to differentiate between different industrial lubricants that are very similar in composition. By expanding the use of valence band photoemission studied to that of difference spectra it has been possible to determine the extent of chemical interaction between an aluminum alloy surface and applied lubricants.; It may be necessary to modify the surface properties by forming a surface film, or modifying the existing oxide film. This film has to be designed so that not only does it meet the desired chemical and mechanical properties, but its application must be easy, financially viable, safe and long lasting. By combining the use of x-ray photoelectron spectroscopy with electrochemical open circuit potential measurements, it has been possible to determine details of surface film formation on aluminum alloys.