Measurement of oxide film growth on Mg and Al surfaces over extended periods using XPS

X-ray photoelectron spectroscopy (XPS) has been used to follow oxide film growth on pure magnesium and pure aluminum surfaces across 12 orders of magnitude exposure to water vapour and humid air. Both Mg and Al exhibited logarithmic-type oxide growth kinetics. Oxide film growth was observed to continue well into the ambinent exposure range, suggesting the possibility for modifying the oxide film chemistry while still under atmospheric conditions. The chemistry of the films was monitored as a function of exposure by examining the changes in the core-level O 1s spectra and the associated oxidised metal/oxygen stoichiometry. It was observed that both Mg and Al surfaces initially formed partially hydrated oxide surfaces which became progressively more hydrated at longer exposures.