Coating systems in atmospheric corrosion environments are usually divided into primers, intermediate paints and topcoats. The main function of the primer is to lay a good foundation on the substrate, have good adhesion to the substrate, and have antirust performance. The primer must have good wetting properties and penetration on the surface of the substrate to enhance the adhesion to the substrate.
The main function of the intermediate paint is to increase the film thickness, so as to play a more effective shielding effect . Generally, the primer and topcoat in the composite coating structure should not be too thick, so the intermediate layer is usually a thixotropic high-solid high-build coating. At the same time, the intermediate paint should be able to play a good role in combining with the primer and topcoat. For machine tools, automobiles, etc., the intermediate layer should also make the surface smooth, which is conducive to topcoat coating. The commonly used intermediate paint is epoxy mica iron intermediate paint.
In heavy-duty anti-corrosion coatings, there is no simple concept of intermediate paint. In many cases, the so-called intermediate paint can be used as a primer used alone, or even as a topcoat for parts that do not require high gloss and aesthetic performance.
The main function of the topcoat is to prevent harmful corrosive media in the external environment, such as oxygen, water vapor, sulfur dioxide and the influence of chemical atmosphere. At the same time, the aesthetic and decorative properties of topcoats are becoming more and more important today. Sometimes, it is also required to coat the outermost layer with a layer of varnish, such as aliphatic polyurethane varnish, etc., to obtain a denser shielding paint film.
