Electrophoresis is divided into anodic electrophoresis and electrophoresis. If the coating particle is negatively charged, the workpiece is an anode and the coating particle is deposited into a film as the anode electrophoresis under the action of the electric field. Conversely, if the paint particle is positively charged, the workpiece is a cathode, and the coating particle is deposited on the workpiece as a membrane called the cathodic electrophoresis. The characteristic of anode electrophoresis is that raw materials are cheap (generally 50% cheaper than cathode electrophoresis); The equipment is simpler and less investment (generally 30% cheaper than cathode electrophoresis); Low technical requirements; The corrosion resistance of the coating is worse than the cathodic electrophoresis (about a quarter of the lifetime of cathode electrophoresis). The reasons for the corrosion resistance of cathodic electrophoretic coating are: the workpiece is the cathode, and the anode is not dissolving, the surface of the workpiece and the phosphating film are not destroyed; Electrophoresis coating (generally containing nitrogen resin) has protective effect on metal and high quality of paint.
Electrophoretic process flow
General metal electrophoresis coating the surface of the whole operation process is as follows: pre-cleaning a launched a degreasing, washing cleaning a washing a medium and a washing, activation of washing a bottom plating washing a bright plating a washed clean a electrophoretic painting a slot on the shearing section.at filter washing a drying test packaging.
The substrate and pretreatment of the coated material have great influence on electrophoresis coating. Therefore, different metal materials and different manufacturing products have different process and pretreatment requirements. The casting is generally used to remove rust from sandblasting or shotcrete, remove the dust from the workpiece surface with cotton yarn, and remove the residual steel balls from the surface with 80# ~ 120# sandpaper. The surface of steel is treated with the removal of oil and rust, and the surface is treated with phosphating and passivation. The black metal workpiece must be phosphating before the anode electrophoresis, otherwise the corrosion resistance of paint film is poor. In the process of phosphating, zinc salt phosphating film is generally used, and the thickness is about 1 ~ 2 mu m, which requires the crystallization of the phosphating film to be fine and uniform.
The process flow of cathodic electrophoresis with different materials is as follows. (1) steel parts
Gold: pretreatment of a nickel plated thin silver transparent gold electrophoresis; Brown: pretreatment of a transparent gold electrophoresis. Bronze color: pretreatment of a galvanized bronze electrophoresis; Black: pretreatment of a black electrophoresis;
Other colors: pretreatment of a nickel - plated, colorless transparent electrophoresis. (2) aluminum and alloy
Gold: pretreatment of a chemical or electrochemical polishing a transparent gold electrophoresis; Coffee color: pretreatment with a transparent brown color electrophoresis; Bronze colour: a bronze electrophoresis before treatment; Black: pretreatment ~ black electrophoresis;
Other colors: a chemical polishing a colorless transparent electrophoresis. (3) zinc alloy
Gold: pretreatment of a base copper an acid copper a bright nickel transparent gold electrophoresis; Coffee color: pretreatment ~ transparent brown color electrophoresis; Bronze colour: a bronze electrophoresis before treatment; Black: pretreatment of a black electrophoresis;
Other colors: pretreatment of a base copper an acid copper a bright nickel a colorless transparent electrophoresis.