Aluminum tubes are widely used, and aluminum tube surface treatment methods are also various types, usually anodizing, chemical conversion treatment, micro-arc oxidation treatment, electroplating treatment, electroless plating treatment or surface organic coating (dusting or painting). The most widely used process is anodizing. Why is anodizing popular?
The anodizing process of aluminum and aluminum alloys has a wide range of applications in the industry, and can be used to prevent corrosion of products or to achieve the dual purpose of protection-decoration, such as wear-resistant layer, electrical insulation layer, spray paint bottom layer and electroplated bottom layer.
1. Prevent corrosion of aluminum products
Since the film layer obtained by anodization itself has sufficient stability in the atmosphere, an oxide film on the surface of the aluminum can be utilized as a protective layer. The oxide film obtained by anodizing aluminum in a chromic acid solution is dense and has good corrosion resistance; the pores of the oxide film obtained from the sulfuric acid solution are larger than the former, but the film layer is thick and the adsorption capacity is strong, if The proper filling and sealing treatment also has good corrosion resistance. In particular, the chromic acid anodization method is particularly suitable for anodizing of rivets and weldments.
2. Protective decorative products
For most of the aluminum and its alloy products that require surface finishing, after chemical or electrochemical polishing, anodizing with a sulfuric acid solution can obtain a highly transparent oxide film. This oxide film can absorb a wide variety of organic and inorganic dyes to have a variety of vivid colors. This color film is both an anti-corrosion layer and a decorative layer. Under some special process conditions, a protective decorative oxide film similar in appearance to porcelain can be obtained.
3. As a hard wear layer
By hard anodizing aluminum and aluminum alloys, a thick and hard Al 2 O 3 film layer can be obtained on the surface thereof. This film not only has a high hardness and thickness, but also has a low roughness. In a sulfuric acid or oxalic acid solution, a hard and thick oxide film can also be obtained on an aluminum article by anodization.
The porous thick oxide film can store lubricating oil, so it can be effectively applied to aluminum products working in a friction state, such as engine cylinders and pistons of automobiles and tractors, which can greatly improve the wear resistance after anodizing.
4. As an electrical insulation layer
The oxide film obtained by anodizing aluminum and aluminum alloy products has a large electrical resistance, so it has a certain effect on improving the electrical insulation of some products, and the dielectric layer of the capacitor can be prepared by anodization, or can be used. Alumina produces an insulating layer for its surface.
5. As the bottom layer of the paint
Due to the porosity and good adsorption capacity of the anodized film, it can be used as a primer layer for spray paint and other organic films, so that the paint film and the organic film are firmly bonded to the product, thereby increasing the corrosion resistance.
6. As the bottom layer of electroplating
Aluminum and aluminum alloy products must be applied to the substrate before plating, before plating. There are many methods for applying the underlayer on the surface of the substrate, and anodizing is one of the important methods in addition to electroplating, zinc immersion, and electroless nickel plating.