Preparation of Gradient Enamel Coating on Aluminum Alloy with Anodic Oxidation

High-performance composite enamel coating was prepared through anodic oxidation technique and low-temperature and fast-sintering technique on the surface of aluminum alloy. Aluminum alloy substrate was placed in sulfuric acid solution for anodic oxidation, and then pores broadened in phosphoric acid solution. Finally, this sample was enameled and sintered, which was compared with the sample without anodic oxidation through scanning electron microscope, metallographic microscope and mechanical tests. The results show that cracks and bubbles appear on the porcelain layer that was enameled directly, while the density and surface finish of the porcelain layer with anodic oxidation are good and the adhesive strength between enamel layer and substrate significantly increase after the transition treatment of anodic oxidation.