Electrophoretic coating (electro-coating) is a coating method in which particles such as pigments and resins suspended in an electrophoretic solution are directionally migrated and deposited on the substrate surface of one of the electrodes by using an external electric field. The basic principle of electrophoretic coating is that the charged paint particles attract the oppositely charged electrodes, and the metal workpiece is immersed in the electrophoretic paint by using a DC power supply. After electrification, the cationic paint particles move to the cathode workpiece, and the anionic paint particles move to the anode workpiece, and then deposit on the workpiece, forming a uniform and continuous coating film on the surface of the workpiece. When the coating film reaches a certain thickness (the resistance of the paint film is large to a certain extent), an insulating layer is formed on the surface of the workpiece, and the "heteropolar attraction" stops, and the electrophoretic coating process ends. The characteristics of electrophoretic coating are: the electrophoretic paint film has the advantages of fullness, uniformity, smoothness and smoothness, and the hardness, adhesion, corrosion resistance, impact performance and penetration performance of the electrophoretic paint film are obviously superior to other coating processes; electrophoretic paint Using water as the dissolving medium saves a lot of organic solvents, greatly reduces air pollution and environmental hazards, is safe and hygienic, and avoids the hidden danger of fire; the electrophoretic coating has high efficiency, small loss of paint, and the utilization rate of paint can reach 90%~ 95%; the thickness of the electrophoretic coating is uniform, the adhesion is strong, and the coating quality is good. All parts of the workpiece such as inner layers, depressions, welds, etc. can obtain a uniform and smooth paint film, which solves the problem of other coating methods for complex shapes. The coating problem of the workpiece; the electrophoresis production efficiency is high, the construction can realize automatic continuous production, which greatly improves the labor efficiency; the electrophoresis equipment is complex, the investment cost is high, the power consumption is large, and the temperature required for drying and curing is high. The management is complex, the construction conditions are strict, and wastewater treatment is required.