With the development of modern industry, the application of light metal materials has become increasingly widespread. Aluminum and aluminum alloys have a series of advantages such as low density, strong electrical and thermal conductivity, excellent mechanical properties, and good workability. They have been widely used in various sectors of the national economy. In the field of construction, for example, 98% of high-rise buildings in Japan use aluminum alloy as door, window and wall decoration. Compared with ordinary wooden doors and windows, steel doors and windows, aluminum alloy doors and windows have the characteristics of light weight, less materials, beautiful appearance, corrosion resistance, and convenient maintenance. Although the cost is 3 to 4 times higher than ordinary wooden doors and windows, the long-term maintenance cost is low, so It has broad prospects for development.
In the atmosphere, the surface of aluminum and aluminum alloy interacts with oxygen to form an oxide film, but the film is thin (3×10-3 ~5×10-3μm), loose and porous, amorphous, uneven and discontinuous The film cannot be used as a reliable protective-decorative film. At present, anodic oxidation or chemical oxidation is widely used in industry to form an oxide film on the surface of aluminum and aluminum alloy parts to achieve the purpose of protection and decoration.
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The thickness of the oxide film obtained by chemical oxidation treatment is generally 0.3~4μm, and its softness, wear resistance and corrosion resistance are all lower than the anodic oxide film. The thickness of the oxide film obtained by anodizing treatment is generally 5-20μm, and the thickness of the hard anodizing film can reach 60-250μm. The film layer is firmly bonded to the base metal and has high corrosion resistance, wear resistance and hardness. The porous oxide film has strong adsorption capacity and is easy to be colored with organic dyes. At the same time, it also has the characteristics of good insulation performance, strong heat insulation and heat resistance.
In summary, the oxide film formed on the surface of aluminum and aluminum alloys after anodizing has good protection-decoration properties. Therefore, it is widely used in aviation, electrical appliances, electronics, machinery manufacturing and light industry.
This experiment is to prepare the protective film on the surface of aluminum alloy by anodic oxidation. Through this experiment, you can understand the basic principles and basic methods of aluminum and aluminum alloy surface treatment, and further understand the anode process in the electrolytic cell through aluminum anodizing.