The passivation process of aluminum is to form a dense oxide film (passivation film) on the metal surface with the chemical action of passivation agent to enhance the corrosion resistance of the metal.
Because aluminum is a relatively active metal, it will spontaneously form a very thin oxide film in the air, and in the atmosphere, it has high corrosion resistance. Because the thickness of the oxide film is relatively thin, the thickness is only about 4 nanometers, and the oxide film has loose structure, porosity, low hardness, poor wear resistance and low mechanical strength. Therefore, in order to achieve the purpose of protection, it is necessary to passivate the aluminum parts and generate a passivating film on the surface to improve the corrosion resistance of the aluminum alloy.