The thickness of the anodized film is generally 5-20V m, and the thickness of the hard anodized film is up to 60-2500m. The film layer also has following characteristics:
1)High Hardness.The hardness of pure aluminum oxide film is higher than that of aluminum oxide film. In general, its hardness is related to the alloy composition of aluminum and the technical conditions of the electrolyte during anodic oxidation. Anodic oxidation film not only has higher hardness, but also has better wear resistance. In particular, the porous oxide film of the surface layer has the ability to adsorb lubricants and further improve the wear resistance of the surface.
2)Has high corrosion resistance.This is due to the high chemical stability of the anodic oxidation film.The anodic oxidation film of pure aluminum has better corrosion resistance than that of aluminum alloy.This is due to the inclusion of alloy components or the formation of metal compounds that cannot be oxidized or dissolved, resulting in discontinuity or void of the oxide film,so that the corrosion resistance of the oxide film is greatly reduced. Therefore, the film obtained by anodic oxidation must be closed to improve its corrosion resistance.
3) Has trong adsorption capacity.The anodic oxidation film of aluminum and aluminum alloy is porous structure with strong adsorption capacity,so filling the pores with various pigments,lubricants,resins and so on can further improve the protective,insulating,wear-resisting and decorative properties of aluminum products.
4) Has good insulation performance.The anodic oxidation film of aluminum and aluminum alloy has no conductive property of metal,and become a good insulating material.
5)It has strong adiabatic heat resistance.This is because the thermal conductivity of anodized film is much lower than that of pure aluminum.The anodic oxidation film can withstand temperature of about 1500℃,while the pure aluminum can only withstand temperature of 660℃.To sum up,after chemical oxidation treatment, especially anodic oxidation treatment,the anodic oxidation film formed on the surface of aluminum and aluminum alloy has good protective and decorative properties.Therefore,it is widely used in aviation,electrical,electronic,machinery manufacturing and light industry,etc.