Surface treatment methods for aluminium sheets

Surface treatment methods for aluminium sheets

1. Electrophoretic coating

Electrophoresis is one of the most effective methods of painting metal workpieces. Electrophoretic painting is a special coating method in which the electrically conductive coated material is dipped in a tank filled with water diluted with a relatively low concentration of electrophoretic paint as the anode (or cathode), and another cathode (or anode) is set up in the tank to pass direct current between the two poles for a period of time to deposit a uniform and fine coating film that is not dissolved by water on the surface of the coated material. The process of electrodeposition coating is accompanied by four chemical-physical changes, namely electrolysis, electrophoresis, electrodeposition and electro-osmosis. This method of treatment is now the most used in Japan. After such treatment, the surface of the aluminium sheet shows a smooth side and the corrosion resistance is enhanced.

2. Powder electrostatic spraying

Electrostatic spraying uses the principle of a high voltage electrostatic corona electric field. The metal conduction cup on the gun head is connected to a high voltage negative electrode and the coated workpiece is grounded to form a positive electrode. A strong electrostatic field is formed between the spray gun and the workpiece. When the carrier gas (compressed air) will be powder coating from the powder supply barrel through the powder delivery tube to the gun's guide cup, its surrounding dense charge, the powder with a negative charge, in the electrostatic force and the role of compressed air, the powder is uniformly adsorbed on the workpiece, by heating, powder melt curing (or plasticising) into a uniform, continuous, flat, smooth coating film. The main feature is to enhance the corrosion resistance of aluminium sheet, for some acid and alkali salt, this kind of aluminium sheet is to be superior to the oxidation coloring profile.