The introduction of Anodizing technology

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 some other functional properties. From this definition, the anodizing of aluminum only includes the part of process of anodizing film formation.

Take metal or alloy as an anode, an oxide film is formed on the surface through electrolysis. Metal oxide film changes the surface state and performance, such as surface color, improve corrosion resistance, enhance wear resistance and hardness, protect the metal surface and so on. For example, aluminum anodizing, aluminum or its alloy placed in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as the anode, under specific conditions and external current, carry out electrolysis. Anodic aluminum or its alloy oxidized, forming a thin layer of alumina oxide on the surface. Its thickness is 5 ~ 30 microns and hard anodic oxide film can reach 25 ~ 150 microns. Anodized aluminum or its alloy, improve its hardness and wear resistance up to 250 ~ 500 kg/mm², good heat resistance. Hard anodized film melting point is up to 2320K, with excellent insulation, and breakdown resistance voltage up to 2000V. It enhances the corrosion resistance that it can stand thousands of hours without corrosion in ω=0.03NaCl salt spray. The thin layer of oxide film has a large number of micro holes, can absorb various lubricants, suitable for manufacture of engine cylinder or other wear-resistant parts. Micro membrane holes have strong adsorption capacity and can be colored into a variety of beautiful and gorgeous colors. Non-ferrous metals or their alloys (such as aluminum, magnesium and their alloys, etc.) can be anodized. This technology is widely applied in mechanical parts, aircraft and automobile parts, precision instruments and radio equipment, daily necessities and architectural decoration.

Generally speaking for anodizing, aluminum or its alloy is taken as the anode and choose lead plate as the cathode, put the aluminum and lead plate together in aqueous solution, which contains sulfuric acid, oxalic acid, chromic acid, etc., then proceed electrolysis, so that the surface of the aluminum and lead plate forms an oxide film. The most widespread of these acids is anodizing with sulfuric acid.