Hardcoat Anodizing

MIL-A-8625/MIL-PRF-8625F Type III is a hardcoat anodizing process for aluminum and its alloys, which provides a very hard, wear-resistant surface compared to Types I and II. The Type III anodizing process is further classified into two classes: Class 1 and Class 2.

Type III, Class 1 involves anodizing aluminum parts to produce a hard, wear-resistant coating with a minimum thickness of 0.001 inches. The process involves immersing the aluminum parts in a sulfuric acid solution and passing an electric current through the solution to produce a thicker layer of anodic oxide on the surface of the aluminum. Class 1 coatings provide increased wear resistance and improved corrosion resistance, making them ideal for applications where parts will be exposed to harsh environments.

Type III, Class 2 involves the same process as Class 1 but with a minimum coating thickness of 0.002 inches. This thicker coating provides even greater wear resistance and is often used in applications where parts are subjected to extreme wear and tear, such as in the aerospace and defense industries.

Type III, Class 1 and Class 2 coatings are extremely hard and provide excellent abrasion resistance, making them ideal for applications such as pistons, gears, and other components that require high durability. However, they are not suitable for decorative applications as the coating is typically dark gray in color and cannot be dyed.