Electrophoretic coating is a coating method that uses an external electric field to make the particles such as pigments and resins suspended in the electrophoretic solution migrate directionally and deposit on the substrate surface of one of the electrodes. The principle of electrophoretic coating was invented in the late 1930s, but this technology was developed and applied in industry only after 1963. Electrophoretic coating is a special film-forming method developed in recent 30 years. It is the most practical construction technology of water-based coatings. It is water-soluble, non-toxic and easy to control automatically. It is widely used in automobile, building materials, hardware, household appliances and other industries.
Electrophoresis is an organic coating, which uses electric current to deposit paint film. Its working principle is "opposites attract".
The basic physical principle of electrophoresis is that charged coating particles attract electrodes with opposite charges. Using DC power supply, immerse the metal workpiece in the electrophoretic paint solution. After power on, the cationic coating particles move to the cathode workpiece, and the anionic coating particles move to the anode workpiece, and then deposit on the workpiece to form a uniform and continuous film on the surface of the workpiece. When the film reaches a certain thickness (the film resistance reaches a certain level), an insulating layer is formed on the surface of the workpiece, "heteropolar attraction" stops, and the electrophoretic coating process ends. The whole electrophoretic coating process can be summarized as the following four steps:
● electrolysis: electrolysis of water
● electrophoresis: apply charged polymer to cathode or anode respectively.
Swimming process
● electrodeposition: the charged polymer is on the cathode or anode respectively.
Polar deposition process
● electroosmosis: the deposited electrophoretic coating shrinks and removes the solvent.
● form a uniform and dense wet film with water.
