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Journal of the Electrochemical Society, Vol.151, No.11, B605-B612, 2004
Surface pretreatments of aluminum alloy AA2024-T3 and formation of chromate conversion coatings - I. Composition and electrochemical behavior of the oxide film
Aluminum alloy AA2024-T3 has been subjected to various pretreatments including those routinely carried out in the industry prior to conversion coating of the alloy. The surface chemistry of the samples after pretreatment was analyzed using variable angle X-ray photoelectron spectroscopy (VAXPS). Electrochemical techniques were used to evaluate the corrosion behavior of the samples in quiescent 0.05 M NaCl solution. The results were compared with those obtained from an untreated sample used in as-received condition that acted as a control. The surface of the alloy was observed to be enriched in copper and magnesium after certain pretreatments. Composition of the surface oxide film as well as the electrochemical behavior was found to vary significantly depending on the pretreatment. In all cases, the overlayer formed on the alloy was less than the sampling depth of the XPS (similar to90 Angstrom). Pretreatment of the alloy using Alconox(R) was found to result in the formation of a highly protective aluminum oxide (Al2O3) surface film. The corrosion current of the samples was observed to be directly proportional to the aluminum oxyhydroxide content of the film, while the polarization resistance of the sample was inversely proportional to the surface copper content. (C) 2004 The Electrochemical Society.