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The coating process of automobile industry directly affects the beauty of the vehicle. Car coating process can be divided into two main parts generally: The first is the surface treatment of the metal before coating, also called pre-treatment of coating technology; the second is construction technology. Surface treatment mainly includes cleaning of oil, dust, rust, and removal of old coating on the surface of the vehicle to improve the surface state of the workpiece and lay the foundation for the next step. The pretreatment includes the mechanical processing and chemical treatment of the surface of the car body according to the damage of various vehicles, such as phosphating, oxidation and passivation.