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 γ-alumina. After an extended holding time at 883 K. the thermally-formed oxide film will be comprised of gibbsite, diaspore, α-Al₂O₃ and γ-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.