What is the surface hardness of alumina plate after anodic oxidation?

The surface hardness of anodized aluminum plate is mainly determined by the aluminum oxide (Al₂O₃) oxide film formed on its surface. The overall hardness is significantly higher than that of pure aluminum plate, and there are obvious differences due to different oxidation process types (conventional anodizing and hard anodizing):

Conventional anodic oxide film: The hardness is usually 3-5 on Mohs hardness (corresponding to Vickers hardness of about 200-300HV). Although it is lower than glass (Mohs hardness of 6-7), it is much higher than pure aluminum plate (Mohs hardness of about 1-2). It can effectively resist daily friction and scratch, and meet the wear-resistant requirements of conventional scenes such as architectural decoration and home appliance shell.

Hard anodic oxide film: By optimizing electrolytic parameters (such as low temperature, high current density and special electrolyte), the film is denser, and the hardness can be improved to 6-7 Mohs hardness (corresponding to Vickers hardness of 350-500HV, and some high-performance films can reach above 600HV), which is close to the hardness level of quenched steel and can withstand severe working conditions such as mechanical wear and impact, and is suitable for automobile engine parts and mechanical guide rails.

In short, the hardness of oxide film is positively related to its density and thickness (hard oxide film is usually thicker, up to 60-200μm), and it can be adapted to the wear resistance requirements of different scenes by adjusting the process.