Inorganic/organic hybrid coatings for aircraft aluminum alloy substrates

A series of water-based stable sol-gel systems have been developed. Various functional groups including amino, epoxy, vinyl, and allyl groups can be i ncorporated into the sol-gel network to interact with organic polymer resin s. The solid content of these sol-gel-based coating formulations varies fro m 2.5 to 45%. The sol-gel coating of alumina-silica networks derived from l ow solid content solutions (2.5%) has been developed and evaluated to repla ce the cut-rent conversion coating pretreatment process. Sol-gel coatings d erived from the high solid content solutions (17-45%) have shown excellent mechanic strength, good adhesion, and provide corrosion protection of the a luminum substrate when cured at elevated temperatures. Sol-gel/epoxy resin hybrid coatings have been formulated and studied. The hybrid coating showed enhanced mechanical strength such as hardness and abrasion resistance. Whe n cured at elevated temperatures (80 degreesC), all of the hybrid coatings studied passed wet adhesion testing. Some of the hybrid coatings pass wet a dhesion testing when cured at room temperature. However, water-sensitivity remains for most of the room temperature cured hybrid coatings. (C) 2001 Pu blished by Elsevier Science B.V.