Before painting, remove all kinds of oil stains (such as lubricating oil, emulsion, grease, sweat, etc.) and dust on the surface of the coated object, and the cleaning process to make the coated surface clean is an indispensable process before the coating process; clean What kind of chemical treatment (or conversion film treatment) or mechanical processing treatment (such as shot blasting treatment) is applied on the coated surface (whether or not), according to the substrate and surface condition of the coating object, the coating process is selected.