Pinhole problems in electrophoretic paint film are not uncommon in industrial production, and they affect the protective performance and appearance of the coating. So, how do these pinholes actually form?

　　Inadequate pretreatment is a significant cause. If impurities such as oil, dirt, yellow rust, and welding flux remain on the workpiece surface, they can become obstacles to the adhesion of the paint film, leading to poor adhesion and the formation of pinholes. For example, incomplete degreasing can leave oil residues that affect subsequent processes; contamination on the phosphating film can also trigger problems.

　　The characteristics of the electrophoretic coating itself can also lead to pinholes. If the content of impurity ions in the coating is too high, such as calcium and magnesium ions, it can reduce the density of the paint film. During electrophoresis, bubbles are generated, forming pinholes. An inappropriate pigment - to - binder ratio can also affect the physical properties of the paint film, making it prone to defects.

　　Construction conditions are also crucial. Both excessively high and low voltages are problematic. Excessively high voltage can cause the surface of the paint film to close prematurely, preventing the escape of bubbles from the bottom layer; excessively low voltage can reduce the fluidity of the paint solution, leading to bubbles being trapped and forming pinholes. If the cleaning after electrophoresis is not timely or the water pressure is too high, the wet paint film may redissolve, resulting in pinholes.

　　To avoid pinholes, measures need to be taken from multiple aspects. Optimize the pretreatment process by using efficient degreasing agents and cleaning agents to ensure the cleanliness of the workpiece surface; adopt high - quality phosphating agents to form a uniform phosphating film; carefully clean the workpiece surface.

　　Choose appropriate electrophoretic paint and control construction parameters. Select the paint according to the substrate and environment to ensure an appropriate pigment - to - binder ratio. Adjust the voltage reasonably, control the ambient humidity, regularly test the impurity ion concentration in the tank solution, and filter the coating in a timely manner.

　　Optimize the cleaning and drying process after electrophoresis. Immediately rinse the workpiece with ultrafiltration solution or pure water after it is taken out of the tank to avoid redissolution of the wet paint film; strictly control the drying temperature and time.

　　Although the pinhole problem in electrophoretic paint film is complex, as long as the pretreatment, coating selection, construction parameters, and subsequent processes are strictly controlled, pinholes can be effectively reduced, ensuring the quality of the paint film and providing reliable protection for industrial products.