The effect of a conversion layer and organic coating on the electrochemical behavior of 8006 and 8079 aluminum alloys

The corrosion behavior of bare and chromate-phosphate treated aluminum alloys 8006 and 8079, employed for the production of heat exchangers, was investigated in aqueous aerated 3.5% NaCl solution using electrochemical impedance spectroscopy (EIS). Experimental results indicate that bare 8079 alloy is less sensitive to corrosion in NaCl containing environments than bare 8006 alloy. This behavior was attributed to the lower content of metallic segregates in the 8079 alloy. For the bare samples, the chromate-phosphate treatment improves the corrosion resistance of both alloys; nevertheless their behavior is still dominated by alloy composition. The application of a polymeric coating, ranging from 5 to 7 mum, provided improved protection for the foils investigated during this study. The reliability of these coatings is however dominated by the application procedure and curing. (C) 2002 Elsevier Science B.V. All rights reserved.