Pre-treatment consists of treating the body with chemical agents. It has two basic functions: to create a layer of much better corrosion resistance and to prepare the body for the next paint layer.
The traditional, and in any case more common, pre-treatment is to degrease the body by removing the welding oils and various metal impurities before applying a substrate of phosphate salts of a few microns. Fidia and Changhong propose low environmental impact solutions with wastewater recirculation systems and low quantities of sludge production. Compact layouts with reduced tanks size and much shorter tunnels.