The electrophoretic coating pickling solution is usually made of inorganic acid plus a certain amount of calcium buffer, inhibitor or surfactant and other additives. Their functions and treatment effects depend not only on the type and function of the dominant acid, but also on the composition of the acid and the additives, their content in water and the ratio between them.

The most important point in the pickling principle is that when acid reacts with iron, hydrogen is generated, which mechanically removes the oxide scale on the surface of the metal substrate. Hydrogen has a positive effect of removing the oxide scale on the substrate surface, but excess hydrogen also has a negative effect of corroding the quality of the metal, causing the metal surface to be filled with hydrogen and making the metal brittle. In order to reduce the damage of "hydrogen embrittlement" to the substrate, a suitable hydrogen retarder is added to the acid. The hydrogen retarder can form a molecular film on the surface of the metal substrate to hinder the further action of the acid, thereby achieving the purpose of corrosion inhibition. The inhibitor has the effect of restraining the dispersion ratio of hydrogen and reducing the evaporation of acid mist. Adding a certain amount of surfactant to the acid solution can make the cleaning solution have the dual effects of degreasing and rust removal.

Advantages of pickling:

The surface obtained after pickling is relatively flat and smooth, which can not only reduce the paint consumption, but also improve the appearance quality of electrophoretic coating that requires high surface flatness;

During pickling, the cleaning liquid penetrates into every corner of the workpiece, so that rust and oil stains are cleaned more completely and thoroughly. As long as the cleaning liquid and its related parameters are well controlled, the treatment quality can be easily guaranteed.