We all know that aluminum is widely used in life and industry, and the surface treatment method of aluminum is also a wide variety, usually aluminum hard oxidation, chemical conversion treatment, micro arc oxidation treatment, electroplating treatment, electroless plating treatment or surface organic coating (spray powder or spray paint) and so on. The most widely used process is anodizing, so why is anodizing "favored"?
The hard oxidation process of aluminum and aluminum alloy has a wide range of applications in industry, which can be used to prevent the corrosion of products or to achieve the dual purpose of protection and decoration, such as as a wear-resistant layer, electrical insulation layer, spray paint bottom and electroplating bottom.
Because the film obtained by anodizing itself has sufficient stability in the atmosphere, the oxide film on the surface of aluminum can be used as a protective layer. The film obtained by anodizing aluminum in chromic acid solution is compact and has good corrosion resistance. The pores of the oxide film obtained from sulfuric acid solution are larger than those of the former, but its film layer is thicker and its adsorption capacity is strong. If it is properly filled and closed, its corrosion resistance is also good. In particular, the chromic acid anodizing method is especially suitable for the anodizing treatment of riveted and welded parts.
2, as an electrical insulation layer
Aluminum and aluminum alloy products after anodizing the oxide film has a large resistance, so it has a certain effect on improving the electrical insulation of some products, can be anodized to prepare the dielectric layer of capacitance, can also be prepared with aluminum oxide for its surface insulation layer.
3, protection - decorative products
For most aluminum and its alloy products requiring surface finishing, after chemical or electrochemical polishing, and then anodizing with sulfuric acid solution, a high transparency oxide film can be obtained. This oxide film can absorb many kinds of organic dyes and inorganic dyes, so that it has a variety of bright colors. This layer of color film is both an anti-corrosion layer and a decorative layer. Under some special technological conditions, protective and decorative oxide film similar in appearance to porcelain can also be obtained.
4, as the bottom layer of electroplating
Before electroplating aluminum and aluminum alloy products, the bottom layer must be applied in advance before electroplating. In addition to electrogalvanizing, zinc dipping and electroless nickel plating, anodic oxidation is also one of the important methods to apply the substrate surface.
5, as the bottom of the paint
Due to the porosity and good adsorption capacity of the anodic oxide film, it can be used as the bottom layer of spray paint and other organic films, so that the paint film and organic film and products are firmly combined together, thereby increasing its corrosion resistance.
6, as a hard wear layer
A thick and hard Al2O3 film can be obtained on the surface of aluminum and aluminum alloys by hard anodizing. This film layer not only has a high hardness and thickness, but also has a low roughness. In sulfuric acid or oxalic acid solution, a hard and thick oxide film can also be obtained on aluminum products by anodic oxidation.
The porous thick oxide film can store lubricating oil, so it can be effectively applied to aluminum products working in friction, such as engine cylinders and pistons of automobiles and tractors, after anodizing, it can greatly improve its wear resistance.