By removing a variety of stains on the surface of the workpiece (such as grease, emulsified oil, vegetable grease, sweat and dirt, etc.) and floating dust, the process of cleaning the surface of the workpiece is an indispensable process for the pre-treatment of the spraying production line. Good pre-treatment facilities and processes are the guarantee of successful spraying. The new pure water system makes the spray powder or paint integrated firmly with the metal surface with strong adhesion, so as to improve the quality of the workpiece and extend the service life of the workpiece!