Anodizing Treatment Of Aluminum Alloys

The Principle Of Anodizing

Using pretreated aluminum as the anode, in an appropriate electrolyte, the process of generating an oxide film (Al2O3 layer) under the action of an applied current is called anodization of aluminum. The principle of aluminum anodization is essentially the principle of water electrolysis.

The Categories of Oxide Film 

The oxide film is divided into two categories: barrier oxide film and porous oxide film. The 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 through.

The most commonly used is the porous oxide film.

Characteristics of Anodized Film

1. The structure of the oxide film is a porous honeycomb knot. The porosity of the film has a good adsorption capacity. It can be used as the bottom layer of the coating layer and can also be dyed to improve the decorative effect of the metal.

2. 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.

3. The corrosion resistance of the oxide film, the aluminum oxide film is very stable in air and soil, and the bonding force with the substrate is also very strong. Generally, after oxidation, it will be dyed and sealed or sprayed to further enhance its corrosion resistance.

4. The bonding force of the oxide film, bonding force between the oxide film and the base metal is very strong, and it is difficult to separate them mechanically. Even if the film layer bends with the metal, the film layer still maintains a good bond with the base metal. However, the plasticity of the oxide film is small and the brittleness is large. When the film is subjected to a large impact load and bending deformation, cracks will occur, so this oxide film is not easy to be used under mechanical action and can be used as the bottom layer of the paint layer.

5. The insulating properties of the oxide film, the resistance of the anodic oxide film of aluminum 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). K). It can be used as the dielectric layer of electrolytic capacitors or the insulating layer of electrical products.