Since the film layer obtained by anodization itself has sufficient stability in the atmosphere, the oxide film on the aluminum surface can be used as a protective layer. The oxide film obtained by anodizing aluminum in chromic acid solution is dense and has good corrosion resistance; the oxide film obtained from sulfuric acid solution has larger pores than the former, but its film layer is thicker and has strong adsorption capacity. Appropriate filling and sealing treatment, its corrosion resistance is also very good. It is particularly pointed out that the chromic acid anodizing method is particularly suitable for the anodizing treatment of riveted parts and welded parts.
For most aluminum and its alloy products that require surface finishing, after chemical or electrochemical polishing, anodizing with sulfuric acid solution can obtain oxide films with higher transparency. This oxide film can adsorb many kinds of organic dyes and inorganic dyes, so it has various bright colors. This color film is both an anti-corrosion layer and a decorative layer. Under some special process conditions, a protective and decorative oxide film similar in appearance to porcelain can also be obtained.
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 high hardness and thickness, but also low roughness. In sulfuric acid or oxalic acid solution, a hard and thick oxide film can also be obtained on aluminum products by anodizing.
The porous thick oxide film can reserve lubricating oil, so it can be effectively applied to aluminum products that work in friction state, such as engine cylinders and pistons of automobiles and tractors, which can greatly improve their wear resistance after anodization.
The oxide film obtained by anodizing aluminum and aluminum alloy products has a large resistance, so it has a certain effect on improving the electrical insulation of certain products. Anodizing can be used to prepare the dielectric layer of capacitors, or it can be used Alumina prepares an insulating layer for its surface.
Due to the porosity and good adsorption capacity of the anodized film, it can be used as the bottom layer of spray paint and other organic films, so that the paint film and organic film can be firmly combined with the product, thereby increasing its corrosion resistance.
Before the aluminum and aluminum alloy products are electroplated, a primer layer must be applied to them before electroplating. There are many methods for applying the bottom layer on the surface of the substrate. In addition to electrogalvanizing, zinc dipping, and electroless nickel plating, anodizing treatment is also one of the important methods.