Synergistic Effects of Hard Anodizing Parameters on the Microstructural, Mechanical, and Tribological Properties of 6061 Aluminum Alloy

The current work delves into the interactive effects of hard anodizing variables, including electrolyte concentration, temperature, current density, and time, on the microstructural, mechanical, and tribological characteristics of 6061 aluminum alloy. The results demonstrate that the final film characteristics are controlled by a kinetic balance between electrochemical oxide formation and chemical dissolution. The influence of electrolyte concentration and temperature was found to be non-monotonic, while a substantial synergistic effect between current density and time was observed. A maximum hardness of 679HV and a thickness of 59µm was achieved using a sulfuric acid concentration of 190g/L, an electrolyte temperature of -2℃, a current density of 4.4A/dm ² , and a duration of 60 minutes. These were considered the optimal anodizing conditions. Tribological examination confirmed the enhanced film’s tribological behavior, exhibiting noticeably lower mass loss and a more stable coefficient of friction than the bare substrate. This enhancement is attributed to a shift in the wear mechanism from severe adhesive wear on the substrate to milder abrasion and, at high loads (50N), brittle fracture on the hard anodic film.