Anodizing of Aluminum

The anodizing of aluminum is an electrolytic oxidation process, in which the surface of aluminum and aluminum alloys is usually transformed into an oxide film, which has protective, decorative, and other functional characteristics. The anodizing of aluminum based on this definition only includes the process of generating an oxide film.

Using metal or alloy components as anodes, an oxide film is formed on their surface through electrolysis. Metal oxide thin films alter the surface state and properties, such as surface coloring, improving corrosion resistance, enhancing wear resistance and hardness, and protecting metal surfaces. For example, aluminum anodizing involves placing aluminum and its alloys in corresponding electrolytes (such as sulfuric acid, chromic acid, oxalic acid, etc.) as anodes, and conducting electrolysis under specific conditions and applied current. The oxidation of aluminum or its alloys on the anode forms a thin layer of aluminum oxide on the surface, with a thickness of 5-30 microns. The hard anodic oxide film can reach 25-150 microns. After anodizing, aluminum or its alloys have improved their hardness and wear resistance, reaching up to 250-500 kg/square millimeter. They have good heat resistance, a hard anodized film melting point of up to 2320K, excellent insulation properties, and a breakdown voltage resistance of up to 2000V, enhancing their corrosion resistance. They do not corrode after thousands of hours in ω=0.03NaCl salt spray. The thin layer of oxide film contains a large number of micropores, which can adsorb various lubricants and are suitable for manufacturing engine cylinders or other wear-resistant parts; The membrane micropores have strong adsorption capacity and can be colored into various beautiful and vibrant colors. Nonferrous metals or their alloys (such as aluminum, magnesium, and their alloys) can be subjected to anodizing treatment, which is widely used in mechanical parts, aircraft and automotive components, precision instruments and wireless equipment, daily necessities, and building decoration.

Generally speaking, aluminum or aluminum alloy is used as the anode, while lead plate is selected as the cathode. Aluminum and lead plate are placed together in an aqueous solution containing sulfuric acid, oxalic acid, chromic acid, etc. for electrolysis, forming an oxide film on the surface of the aluminum and lead plate. Among these acids, the most widely used is anodizing with sulfuric acid.

Foshan Golden Source Precision producing wide range of aluminum machining parts and welded articles. We have 4-meter anodizing tanks, 7-meter anodizing tanks, 14-meter anodizing tanks and we can handle profiles with a max length of 12 meters. Normal anodizing fishes are: natural silver anodize, clear anodize, bright dip anodize, black anodize, bronze anodize, grey anodize. Relative surface treatment are: polishing, brush, sandblast. All these finishes are handled in house.