Comparison of corrosion resistance of general purpose enamel coating with coating developed for aerospace applications

The study pertains to the comparison of corrosion resistance offered by commercially available enamel coating with the organic coating of aerospace applications applied on AA2024 alloy. The poor corrosion resistance of AA 2024 alloy is mainly due to CuAl2 and CuMgAl2 precipitates, which strengthens the alloy through age hardening. In the present study two layers of organic coating have been given on zinc rich self etch primer under coat. General-purpose enamel finish coat, Epoxy based alkyd finish coat, and polyurethane based finish coat have been used as topcoats. Electrochemical impedance spectroscopy has been used to evaluate the corrosion resistance of the coated surfaces. The combination of zinc rich self etch primer and enamel is found to be having lowest corrosion protection and zinc rich self etch primer with polyurethane based topcoat is having the highest corrosion protection value. The lower corrosion protection value of the coated surface with zinc rich etch primer and enamel topcoat may be attributed to the formation of a polymeric film which is highly permeable to the corrodent. © 2004 SAEST.