Improved Chromic Acid Anodize Seal for Optimum Paint Adhesion

A new anodize sealing process using a dilute solution of chromic acid and metal chromates in deionized water has been developed. Use of this process to seal chromic acid anodize layers gives films that have excellent paint adhesion while maintaining specification requirements for salt-spray corrosion resistance. The extent of hydration is easier to control than with conventional sealing methods and does not require monitoring. Extensive laboratory testing has defined optimum operating parameters. Examination of sealed films using scanning/transmission electron microscopy has elucidated the anodize film structures controlling paint adhesion and corrosion resistance.