Hard Coat Aluminum Anodizing

摘要

Type HI anodized aluminum is specifically designed for high-wear applications, such as pistons, transmission parts, and frying pans. Often referred to as "hard coat," Type III is described in the military specification MIL 8625 as a nominal coating thickness of 0.002 In. with specific wear properties. To achieve this, the anodizing must be done quickly and under conditions that minimize chemical attack of the oxide coating. This lowers the coating's porosity, which, in turn, Improves its wear resistance. Conventional hard coat is produced in a very cold sulfuric acid bath-usually around 28°F-using high current density.