<i>In situ</i> ellipsometric and electrochemical characterisation of oxide formed on aluminium in acetate buffer

The paper presents methodology for characterisation of oxide properties on pure aluminium in aqueous solution by use of visual light ellipsometry (VISSE) and electrochemical impedance spectroscopy (EIS) under controlled environmental conditions. Control of the electrode potential and solution pH, chemistry and temperature gives well-defined and reproducible oxide properties. Monitoring the current density during transition between different applied potentials gives direct information about Faradaic changes in the oxide properties, while the ellipsometer monitors the changes in the actual thickness and refractive index of the film. EIS reveals in turn information about the charge transfer processes and adsorption at steady-state conditions. Physical significance of the parameters calculated from the experimental data depends on the accuracy of the mathematical models used. Preliminary results are presented for acetate adsorption and oxide film growth and dissolution kinetics in an aqueous environment. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)