[China Aluminum Network] The purpose of the oxidation process is to obtain a protective film to prevent natural oxidation, and the surface hardness of the oxide film is also higher than the raw material, which can play a protective role. The national standard of the door and window fittings is: aa8-10μm, exported to EU standards: 10-15μm. The product has a thick oxide film, strong anti-oxidation ability, good abrasion resistance (protection of the surface), and long durability.
Surface oxidation of aluminum and aluminum alloys is an important surface treatment process in the processing of aluminum products.
Although aluminum and aluminum alloys can naturally form an oxide film in the atmosphere, the film is thin (40-50A) and porous, non-uniform and non-continuous film layer, and can not be used as a reliable protective-decorative film layer.
Anodizing or chemical oxidation methods are increasingly used to create an oxide film on the surface of aluminum and aluminum alloy parts to achieve protection and decoration effects. Lan Zongbao, Chairman of Foshan Baogao Aluminum Door and Window Accessories Co., Ltd., said: “The product surface oxidation treatment and process are very important for product quality, mainly reflected in the oxidation process and oxidation time. The thicker the film on the surface of the product, the more durable. Bao Gao's all oxidation products have to be strictly controlled and conform to national standards, and the professional acid salt spray test can reach more than 96 hours. It is equivalent to more than 15 years of normal corrosion in normal natural environments."
The oxide film obtained by chemical oxidation treatment generally has a thickness of 0.3-4 um, and the softness, wear resistance and corrosion resistance are lower than those of the anodic oxidation film. Therefore, except for special purposes, it is rarely used alone. However, it has a good adsorption capacity, and its surface is painted again, which can effectively improve the corrosion resistance and decorative properties of aluminum products. The oxide film obtained by anodizing treatment generally has a thickness of 5-20 vm, and a hard anodized film thickness of 60-2500 m. Its film also has the following properties:
(1) The hardness of aluminum processing is high. The hardness of the pure aluminum oxide film is higher than that of the aluminum alloy oxide film. In general, its hardness is related to the alloy composition of aluminum and the process conditions of the electrolyte during anodization. Anodized film not only has higher hardness but also better wear resistance. In particular, the porous oxide film on the surface layer has the ability to adsorb lubricant, and can further improve the surface wear resistance.
(2) Aluminum has higher corrosion resistance. This is due to the high chemical stability of the anodized film. After testing, the anodized film of pure aluminum has better corrosion resistance than the anodized film of aluminum alloy. This is because the inclusion of an alloy component or the formation of a metal compound cannot be oxidized or dissolved, so that the oxide film is discontinuous or voids are generated, and the corrosion resistance of the oxide film is greatly reduced. Therefore, the film obtained after anodization is generally subjected to a sealing treatment in order to improve its corrosion resistance.
(3) Aluminum processing has strong adsorption capacity. The anodized film of aluminum and aluminum alloys is a porous structure with a strong adsorption capacity, so filling the holes with various pigments, lubricants, resins, etc. can further improve the protection, insulation, wear resistance and decorative performance of aluminum products.
(4) Aluminum processing has good insulation properties. Anodized films of aluminum and aluminum alloys do not have the conductive properties of metals and have become good insulating materials.
(5) Strong thermal insulation and heat resistance. This is because the thermal conductivity of the anodic oxide film is much lower than that of the pure aluminum anodic oxide film, which is about 15001C, while pure aluminum can only withstand 660°C. To sum up, aluminum oxides and aluminum alloys have been chemically oxidized, especially anodized, and the oxide film formed on the surface of the aluminum and aluminum alloys has good protection and decoration characteristics. Therefore, it is widely used in aviation, electrical, electronics, machinery manufacturing and light industry.