The surface treatment of metal before painting generally includes degreasing, rust removal and oxidation. This is a key link that affects the entire coating effect. So, in the entire surface treatment process, how to do it? Let's take a look at the analysis below.

Degreasing

Divided into physical-mechanical methods and physical-chemical methods, the former includes wiping method, combustion method and injection method. The degreasing methods used before automobile painting are mainly physical and chemical methods, including lye degreasing method, emulsion degreasing method and solvent degreasing method.

The lye degreasing method mainly removes grease through saponification. When removing unsaponifiable mineral oil, it helps emulsification and degreasing by the action of surfactants. The emulsion degreasing method is a mixed solution composed of adding one or more surfactants in an organic solvent, or adding a weak three-property detergent.

Rust removal

It is to remove the oxides and hydroxides generated on the metal surface. The method of rust removal is usually selected according to the color of the rust, the generation state and the procedure.

Derusting methods can be divided into two categories: physical derusting and chemical derusting. There are two types of physical rust removal: manual rust removal and mechanical rust removal. Chemical rust removal commonly used pickling rust removal method.

The commonly used chemical rust removal method is the pickling method, that is, the metal is immersed in an acid solution, so that the oxides and hydroxides attached to the metal surface undergo a chemical reaction and dissolve in the acid solution to remove the rust.

Oxidation

Oxidation treatment is a method in which the metal surface undergoes a certain chemical treatment, so that a layer of insoluble, phosphating double salt protective film is formed on the metal surface. Phosphating is widely used in the automotive industry for panels, cabs, body panels, etc.

As a surface treatment before painting, it can increase the adhesion and corrosion resistance of the coating film.

Through the above analysis, we know the surface treatment of metal before painting. The surface treatment is good, which is very helpful for the whole painting process in the later stage.