Cold galvanized coatings are mainly used for corrosion protection through electrochemical principles. Therefore, it is necessary to ensure that the zinc powder is in full contact with the steel, resulting in an electrode potential difference, so the surface treatment of the steel is very important. Before spraying cold galvanizing, mechanical rust removal (sand blasting, shot blasting, etc.) should be selected to make the surface cleanliness of the steel reach ISO 85O1-1 Sa 2.5, which is equivalent to GB 8923 Sa 2.5. Its text is defined as: "After the steel is mechanically derusted, the surface is free of oil, rust, scale and other dirt, or only slight traces are left; 95% of the steel surface is impacted by steel shot (sand) and exposed. Metallic sheen."

For another indicator of surface treatment quality - roughness, different cold galvanized materials have different requirements for roughness. In the construction instructions of Zinga, the average roughness Ra=12.5 is required, that is, the roughness Rz=55-75 microns. In the "Strong Zinc" and "Robalu" construction instructions, the requirements for roughness are slightly lower, Rz=40~60 microns.

If the cold galvanized film is formed alone, as an anti-corrosion coating, the surface roughness can be controlled to be slightly smaller to ensure the coating thickness of the cold galvanized coating; and when the cold galvanized coating is used as the bottom layer of the heavy-duty anti-corrosion coating, the total matching coating When the thickness is greater than 180 microns, in order to ensure the adhesion of the entire coating, the surface roughness Rz of the steel should be greater than 60 microns.