Potentiodynamic evaluation of sol-gel coatings with inorganic inhibitors

Sol-gel coatings were investigated as potential replacements for chromate-based surface treatments on aircraft aluminum alloys. Unlike chromate based treatments current sol-gel coatings do not have the ability to leach corrosion inhibitors upon coating damage and minimize corrosion of the unprotected area. As an alternative, environmentally compliant non-chromate inhibitors of Ce(NO3)(3), NaVO3 and Na2MoO4 were incorporated into a Zr-epoxy soi-gel, Results are reported on the coatings chemical analysis and their corrosion protection performance based on electrochemical studies. Aluminum alloy 2024-T3 test coupons coated with protective sol-gel films were found to provide considerable corrosion protection. The improved performance characteristics were derived from the sol-gel ability to form a uniform, low defect, barrier coating. Coatings doped with Ce(NO3)(3) had barrier properties at Least as good as the standard sol-gel coatings. Coatings with Na2MoO4 and NaVO3 did not provide adequate corrosion protection. The use of corrosion inhibitors within organically modified sol-gel coatings is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.