The future automobile industry shall develop in the direction of no-pollution,energy-conservation and emission-reduction.Efforts should be made to optimize production capacity and to promot scientific and technological production.In order to solve problems of the traditional phosphating pretreatment coating like high energy consumption and serious pollution,we must first solve the serious pollution phosphating process.Thin-film pretreatment has been developed in the market to replace the traditional phosphating.However,poor control of thin-film pretreatment will affect the corrosion protection of the whole vehicle,so thin-film pretreatment is relatively less used in the industry currently.