Corrosion resistant high-silica-zeolite MFI coating - One general solution formulation for aluminum alloy AA-2024-T3, AA-5052-H32, AA-6061-T4, and AA-7075-T6

Corrosion resistant high-silica-zeolite (HSZ) MFI coatings have been synthesized by in situ crystallization using a single solution formulation on a series of aluminum alloys with rather different chemical compositions including AA-2024-T3, AA-5052-H32, AA-6061-T4, and AA-7075-T6. The coatings are continuous, compact, and of uniform thickness (similar to 10 mu m). The coatings are demonstrated by using ASTM D 3359B-02 method to have excellent adhesion to all metal substrates tested. The cross-sectional composition analysis shows a gradual and continuous change of Si/Al ratio from pure aluminum at the substrate surface to almost infinity at the free coating surface, and this is suggested to be the origin of excellent of adhesion observed. In addition, a simple detergent solution pretreatment is shown to be adequate for the reproducible formation of high quality coatings. (c) 2006 The Electrochemical Society.