Thermally-Formed Oxide on Aluminum and Magnesium

Pure aluminum and magnesium cube samples were heated at a specific temperature for a given time after being polished by abrasive papers. The amorphous layer that formed on the sample surface was transformed into a crystallized oxide film during the heating and holding period. We discuss how this thermally-formed oxide film progressively developed on the surface of the cubic samples. Gibbsite (Al(OH)3) forms on pure aluminum during the initial stage of heating, after which it is then transformed to complex oxides, diaspore and (gamma) -alumina. After an extended holding time at 883 K, the thermally-formed oxide film will be comprised of gibbsite, diaspore, (alpha) -Al2O3 and (gamma) -alumina. This thermally-formed oxide film is compact and contains evenly-distributed microchannels. With pure magnesium, the transformation of periclase from brucite is associated with the formation of microcracks. In this study we use TGA (thermo-gravimetric analysis) to describe the progressive development of complex oxides and periclase films on pure Al and Mg respectively.