1.Definition of anodizing
Anodizing is a kind of electrolytic oxidation, during which the surface of aluminum alloy is usually transformed into a layer of oxide film, which has protective, decorative and other functions.
2. Classification of anodic oxide film
There are two types of oxide film: barrier oxide film and porous oxide film. Barrier oxide film is a dense and non-porous thin oxide film close to the metal surface. The thickness depends on the applied voltage and generally does not exceed 0.1um. The porous oxide film is composed of a barrier layer and a porous layer. The thickness of the barrier layer is related to the applied voltage, and the thickness of the porous layer depends on the amount of electricity passed. The most commonly used one is porous oxide film.
3. The characteristics of anodized film
a. The structure of the oxide film presents a porous honeycomb structure. The porosity of the film makes it have a good adsorption capacity. It can be used as the bottom layer of the coating layer and can be dyed to improve the decorative effect of the metal.
b. The hardness of the oxide film is high, and the hardness of the anodic oxide film is very high, and its hardness is about 196-490HV, because the high hardness determines the wear resistance of the oxide film is very good.
c. The corrosion resistance of the oxide film. The aluminum oxide film is stable in air and soil, and has a strong binding force with the substrate. Generally, it will be dyed and sealed or sprayed after oxidation to further enhance its corrosion resistance. .
d. The bonding force of the oxide film. The bonding force between the oxide film and the base metal is very strong. It is difficult to separate them by mechanical methods. Even if the film layer is bent with the metal, the film layer still maintains a good bond with the base metal, but the oxidation The film has small plasticity and high brittleness. When the film layer is subjected to a large impact load and bending deformation, cracks will occur. Therefore, this oxide film is not easy to use under mechanical action and can be used as the bottom layer of the paint layer.
e. The insulation of the oxide film, the resistance of aluminum anodized film is high, the thermal conductivity is also very low, the thermal stability can be as high as 1500 degrees, and the thermal conductivity is 0.419W/(m-K)—1.26 W/(m-K). It can be used as the dielectric layer of electrolytic capacitors or the insulating layer of electrical products.