Electrochemical evaluation of a new type of corrosion passivation layer:: Artificially produced Al2O3 films on aluminum

A recently developed technique for the artificial production of an Al2O3 film on ultrahigh-purity polycrystalline Al samples was employed. Electrochemical impedance spectroscopy (EIS), Auger electron spectroscopy (AES), and grazing angle X-ray diffraction (GAXRD) were used to investigate the artificial oxide film. The growth of aluminum oxide in water vapor (5 x 10(-7) Torr) enhanced by 100 eV electron bombardment resulted in an artificial oxide film which exhibited a 10-30-fold improvement in electrical resistance in 3.5% NaCl solution compared to oxide films of the same thickness grown at 300 K in the absence of electron bombardment (thermal excitation only). These measurements suggest that the artificial aluminum oxide film may provide superior corrosion passivation qualities compared to thermally grown oxide films. The amorphous nature of the artificial oxide film was confirmed by GAXRD.