The galvanized steel coil that usually require anti-corrosion coating are mainly hot dip galvanized steel and thermal spray zinc steel. Zinc is a reactive metal. The purpose of the zinc coating is to provide cathodic protection against rust. This function is the same as zinc-rich primer.
The surface coated with zinc metal coating has the following differences compared to bare steel:
1. Whether it is hot dip galvanized steel or hot sprayed zinc steel, the surface is usually smooth, and it is impossible to spray clean as bare steel to meet certain roughness requirements;
2. The surface of the active zinc will be exposed to zinc for a period of time;
3. Active zinc is easily saponified with some active ingredients in fatty acids or other paints in some oil paints (such as alkyd, phenolic, etc.)
4. Since the zinc metal coating is already provided for protection, the protective coating coating system of the post-coating can be correspondingly thinned.