The phosphating treatment before priming, will improve the adhesion of the metal film and the substrate, to improve the corrosion resistance of the coating system; provided step in order to avoid the formation of secondary rust protection. The most important issue of the paint before the phosphating phosphate coating and primer must have excellent supporting, phosphate coating rust is secondary, detailed and dense phosphate coating, thin film. When the phosphate coating is thick, the film's overall performance would produce a negative effect. Phosphate system and process selected by: workpiece material, the degree of oil rust, geometry; the phosphide painted interval; decision the primer varieties and construction as well as space and equipment conditions.