Influence of Two-step Anodizing on Anodic Film Structure and Corrosion Resistance on AA6061

This paper aims to study the influence of one-step anodization and two-step anodization on structure of the anodic film on 6061 aluminum alloy under the same process parameters. The corresponding relationship between matrix structure difference and film growth behavior and performance was explored. The commercial 6061 aluminum alloy and SPS powder sintered aluminum alloy were used as the research objects. Furthermore, systematic research was carried out on the influence of different substrates on the film structure during the one-step and two-step anodizing processes. At the same time, sealing post-treatment was carried out in accordance with the structural characteristics of different anodic films, and the corrosion resistance of the film was analyzed and compared by the electrochemical test method. Compared with the one-step anodizing, the result shows that the two-step anodizing current density of commercial 6061 aluminum alloy and SPS aluminum alloy increased from 12.07 and 56.62 mA/cm² to 13.68 and 64.8 mA/cm², respectively and the film growth rate has increased significantly. The orderly pit structure formed on the substrate surface after the one-step anodizing helps to improve the regularity of the pore structure in the two-step anodizing. While the holes in the SPS sintered aluminum alloy anodic film are in a regular "hexagonal" structure. A two-step anodizing can effectively reduce the distribution of cathodic intermetallic particles on the substrate surface, which can not only improve the integrity of the anodic film, but also enhance the corrosion resistance of the corresponding film. In conclusion, the two-step anodizing can make the anodic film integrity and regular, and the overall corrosion resistance is significantly improved.