Performance Comparison of Steam-Based and Chromate Conversion Coatings on Aluminum Alloy 6060

In this study, oxide layers generated on aluminum alloy 6060 (UNS A96060) using a steam-based process were compared with conventional chromate and chromate-phosphate conversion coatings. Chemical composition and microstructure of the conversion coatings were investigated and their corrosion performance was evaluated using potentiodynamic polarization, acetic acid salt spray, and filiform corrosion testing of powder coated specimens. The steam-based process resulted in homogenous growth of oxide layer and superior coverage over intermetallic particles when compared to chromate-based conversion coatings. The coating formed by steam showed improved corrosion resistance, while adhesion to powder coating and filiform corrosion was comparable with chromate conversion coatings.