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The growth mechanism and electrochemical properties of the oxide film on aluminium in simulated acid rain

The growth mechanism and properties of the oxide films on aluminium were studied in simulated acid rain (pH 4.5) by electrochemical techniques, cyclic voltammetry and electrochemical impedance spectroscopy. The potentiodynamic formation of anodic oxide film on aluminium surface was described in terms of high field model. This is justified by the obtained values of kinetic parameters: the electric field strength (~106 V cm–1 ), ionic conductivity through the film (~10–12 S cm–1 ) and half jump distance (~0.15 nm). The structural and protective properties of passive oxide films formed spontaneously at the open circuit potential were studied using electrochemical impedance spectroscopy in the wide frequency range. The impedance data shows that protective passive oxide film on aluminium can be formed spontaneously at the open circuit potential in the studied solution with a resistance over 100 kΩ cm2 . The concentration of the metallic ions released into solution and measured by atomic absorption spectrometry was in accordance with the results obtained from the electrochemical techniques.

aluminium, anodic film, simulated acid rain, cyclic voltammetry, electrochemical impedance spectroscopy, atomic absorption spectrometry

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