After aluminum is subjected to anodic oxidation, a dense film layer (ranging from several micrometers to several hundred micrometers) can be obtained on the surface of aluminum and its alloys, which is much thicker than the natural oxide layer. After the artificial oxide film is sealed, the amorphous oxide film transforms into a crystalline oxide film, and the pores are also sealed, allowing the luster of the metal surface to remain unchanged for a long time, improving corrosion resistance and mechanical strength. After coloring, a decorative appearance can be achieved. Due to the many properties of aluminum and its alloy products after anodic oxidation, anodic oxidation technology is widely used in the surface treatment of aluminum products. Industrial applications can be roughly divided into the following categories. 

Preventing product corrosion: Due to the appropriate sealing treatment, the oxide film obtained through anodization has excellent stability in the atmosphere. Whether the oxide film obtained from sulfuric acid solution, oxalic acid solution or chromic acid solution in the normal process, its corrosion resistance is very good, such as daily-use aluminum pots, bowls, plates and pans, and the inner tank of washing machines. The chromic acid oxidation method is particularly suitable for aluminum welding parts and riveted parts. 
2. Protection and Decoration: On the transparent oxide film, the oxide film has the property of adsorbing various organic dyes or inorganic pigments. Various bright colors and patterns can be obtained on the oxide film. Moreover, in recent years, many new technologies have emerged, such as one-time oxidation with multiple colorings, wood grain patterns, oxide offset transfer printing, and porcelain oxidation. These have made the appearance of aluminum more beautiful and pleasing to the eye. This colored film serves as both a decorative layer and a protective layer. For example, it is used in lighters and porcelain. 
3. As a hard wear-resistant layer: By adjusting the process conditions of anodizing in sulfuric acid or oxalic acid solutions, a thicker hard film can be obtained. The porosity and adsorption properties of the film can be used to store the selected oil, and it can be effectively applied in working conditions under friction, possessing the characteristics of lubrication and wear resistance, such as engine cylinders and pistons of cars and tractors. 
4. As an electrical insulating layer: The oxide film of aluminum and its alloys has the characteristic of high resistance, and the thickness of the film is directly proportional to the resistance. As an electrical insulating layer, this property has certain practical significance. It can be used as the dielectric of a capacitor, or as the outer sheath of a cable, and its surface can be used as an insulating layer instead of a plastic sheath or a plastic sheath. It is quite popular abroad. When the film thickness is 27.5 micrometers, its breakdown voltage is 441V. If the film pores are filled with phenolic resin, the withstand voltage can be increased by twice. In an oxalic acid solution, when the film thickness increases, a high-quality insulating layer with a resistance of 200 and a breakdown voltage of 980V can be obtained. Of course, this property can be used not only for wires, but also for other electrical appliances. 
5. As the base layer for painting and electroplating: Due to the porous nature and excellent adsorption capacity of the oxide film layer, it has good adhesion to the paint film and organic films, thus it can be used as the base layer for painting. The film obtained by phosphoric acid anodic oxidation can be used as the base layer for electroplating on aluminum. 
6. For modern architecture: Due to the introduction of aluminum alloy electrolytic coloring technology, in recent years, more and more aluminum profiles used in Chinese architecture have adopted electrolytic coloring. It not only has bronze, black and red colors suitable for architectural use, but also has better wear resistance than the common conventional oxidation. Particularly worth mentioning is that it has better light fastness, and does not fade even after being exposed to night-time sunlight for 20 years. This is incomparable to the oxidized coloring. Electrolytic aluminum profiles can not only be used for architectural doors and windows, but also for store counters and shelves.