Anodizing

After the metal material or product is surface anodized, its corrosion resistance, hardness, wear resistance, insulation and heat resistance have been greatly improved. The metal material that is most anodized is aluminum. Anodizing of aluminum is generally carried out in an acidic electrolyte, with aluminum as the anode. In the electrolysis process, oxygen anions react with aluminum to produce an oxide film. This kind of film is not fine enough when it is initially formed. Although it has a certain resistance, the negative oxygen ions in the electrolyte can still reach the aluminum surface to continue to form an oxide film. As the thickness of the film increases, the resistance also increases, so that the electrolytic current becomes smaller. At this time, the outer oxide film in contact with the electrolyte is chemically dissolved. When the rate of oxide formation on the aluminum surface is gradually balanced with the rate of chemical dissolution, this oxide film can reach the maximum thickness under this electrolytic parameter. The outer layer of aluminum's anodized film is porous and easily absorbs dyes and colored substances, so it can be dyed and improve its decorativeness. After the oxide film is sealed with hot water, high temperature steam or nickel salt, it can further improve its corrosion resistance and wear resistance. In addition to aluminum, industrially anodized metals include magnesium alloys, copper and copper alloys, zinc and zinc alloys, steel, cadmium, tantalum, zirconium, etc.