Surface treatment is an indispensable process in sheet metal processing. It mainly plays a role of decoration and protection on the surface of the product. Nowadays, in the sheet metal processing industry, the more commonly used surface treatment methods include electroplating, Spraying, oxidation, sandblasting and so on. The procedures of these surface treatment processes are roughly the same, so the procedures of this type of surface treatment process are briefly introduced here.
Surface pretreatment generally has two treatment processes: chemical conversion and degreasing. Degreasing is treated with a special degreasing agent. The purpose of degreasing is to remove the dirt, grease, etc. attached to the surface of the aluminum material during the processing process, as well as to remove the oxide film on the surface.
Chemical conversion treatment is usually chromization treatment or phosphorus-chromization treatment. The purpose is to form a chemical conversion film (such as a chromized film or a phosphorous-chromized film) on the surface of the substrate, which can not only enhance the adhesion between the substrate and the coating, but also protect the substrate.
The pretreatment is followed by a drying treatment, which generally includes natural drying and high-temperature drying to remove the moisture in the pretreatment process.
Among them, our company uses high-temperature drying. High-temperature drying does not have a long time for natural drying, low efficiency, and incomplete drying leads to rust and other shortcomings. When drying, you only need to control the drying temperature to quickly dry the surface of the substrate.
In order to prevent the temperature from being too high, the chemical conversion film produced by the pretreatment is excessively dehydrated and destroyed. Our general drying temperature after chromization treatment is not higher than 65℃. The drying temperature of phosphorous-chromizing treatment is not higher than 85°C.
The powder unspraying treatment is to apply the powder coating to the surface of the aluminum alloy profile through a powder spray gun to form a protective and decorative organic polymer film. Electrostatic powder spraying is to apply negative high voltage to the spray gun and ground the workpiece to form a high-voltage electrostatic field between the spray gun and the workpiece. The electrostatic liquid phase spraying process is to apply the liquid paint to the surface of the aluminum alloy profile through the electrostatic spray gun to form a protective and decorative organic polymer film. For acrylic paint spraying and polyester paint spraying, brushing is generally used, that is, a layer of paint film is formed, while fluorocarbon paint spraying generally needs to be treated with two coatings, three coatings or four coatings.