Anodizing and Coloring Aluminum Alloys

In this experiment, wrought aluminum alloys, fashioned into 3 in. X 1 in. coupons, were anodized and subsequently colored. To achieve the most attractive colors the 1100 Al alloy was selected over other wrought Al alloys. To further ensure attractive colors, an eight-step pretreatment protocol was followed. Sulfuric acid was used as the electrolyte solution in the anodizing bath, and a five-step post-treatment protocol was followed prior to coloring the anodized Al coupon. Inorganic pigments (yielding gold and Prussian blue) and electrolytic coloring (yielding burgundy red) were utilized to achieve the colored Al alloys. Using oxalic acid in place of sulfuric acid as the electrolyte solution in the anodizing bath and anodizing other wrought Al alloys, namely, the 2024, 3003, 5052, 6063, and 7075 wrought Al alloys, was also explored. This experiment was performed during two successive 3 h laboratory periods in a second-semester general chemistry course designed for undergraduate engineering students.