Objective: To remove a layer of corrosion-resistant "phosphating layer" that enhances the adhesion of the coating on the surface of the workpiece. The main process steps: degreasing, derusting, phosphating, and passivation. After pretreatment, the workpiece surface is not only free of oil, rust, and dust, but also forms a uniform, rough, and rust-resistant gray phosphating film on the originally silver-white and glossy surface. This film can both remove rust and increase the adhesion of the plastic coating layer. Related equipment: pretreatment tank. Related materials (chemicals): sulfuric acid, hydrochloric acid, soda ash, acidic degreasing agent, phosphating solution, passivating solution.

Spray-type multi-station pretreatment is commonly used equipment in surface treatment. Its principle is to use mechanical scrubbing to accelerate chemical reactions and complete processes such as degreasing, phosphating, and washing. A typical process for spray-type pretreatment of steel parts includes: pre-degreasing, degreasing, washing, washing, and pure water washing. Pretreatment can also employ a shot blasting machine, suitable for structurally simple steel parts that are severely rusted and either free of oil or lightly oiled. Additionally, it does not cause water pollution.