What are the other characteristics of the film of aluminum and aluminum alloys after anodizing?

With the development of modern industry, light metal materials are used more and more widely. Aluminum and aluminum alloy have a series of advantages such as low density, strong electrical and thermal conductivity, excellent mechanical properties, good machinability, etc., and have been widely used in various sectors of the national economy. In the field of construction, 98% of high-rise buildings in Japan use aluminum alloy as doors, Windows and wall decoration. Compared with ordinary wood doors and Windows, steel doors and Windows, aluminum alloy doors and Windows have the characteristics of light weight, material province, beauty, corrosion resistance, convenient maintenance, etc., although the cost is 3 to 4 times higher than ordinary wood doors and Windows, but because of the low long-term maintenance cost, it has broad prospects for development.

In the atmosphere aluminum and aluminum alloy surface and oxygen can form a layer of oxide film, but the film is thin (3×10-3~5×10-3μm) and loose porous, amorphous, uneven and discontinuous film layer, can not be used as a reliable protective decorative film. At present, aluminum oxidation treatment methods of anodic oxidation or chemical oxidation are widely used in industry to generate an oxide film on the surface of aluminum and aluminum alloy parts to achieve the purpose of protection and decoration.

The thickness of the oxide film obtained by chemical color oxidation treatment is generally 0.3~4μm, and the soft quality, wear resistance and corrosion resistance are lower than that of the anodic oxide film. The thickness of the oxide film obtained by anodic oxidation treatment is generally 5~20μm, and the thickness of the hard anodic oxide film can reach 60~250μm, and the film layer is firmly combined with the base metal, and has high corrosion resistance, wear resistance and hardness. The porous oxide film has strong adsorption capacity, is easy to be colored with organic dyes, and has good insulation properties and strong adiabatic heat resistance.

In summary, aluminum oxidation processing believes that after aluminum and aluminum alloy are anodized, the oxide film formed on their surface has good protective and decorative characteristics. Therefore, it is widely used in aviation, electrical appliances, electronics, machinery manufacturing and light industry.

The hardness of pure aluminum oxide film is higher than that of aluminum oxide film. Usually, its hardness is related to the alloy composition of aluminum and the technical conditions of the electrolyte during anodizing. The anodic oxide 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 absorb lubricant, and can further improve the wear resistance of the surface.

This is due to the high chemical stability of the anodic oxide film. The test shows that the anodized film of pure aluminum has better corrosion resistance than that of aluminum alloy. This is because the alloy component inclusion or formation of metal compounds can not be oxidized or dissolved, so that the sandblasted oxide film is discontinuous or void, so that the corrosion resistance of the oxide film is greatly reduced. Therefore, the film obtained after anodizing must be closed in order to improve its corrosion resistance.

The anodized film of aluminum and aluminum alloy has a porous structure and strong adsorption capacity, so filling the hole with various pigments, lubricants, resins, etc., can further improve the protection, insulation, wear resistance and decorative properties of aluminum products.

This is because the thermal conductivity of the anodized film is much lower than that of pure aluminum, and the anodized film can withstand a temperature of about 1500 ° C, while pure aluminum can only withstand 660 ° C.