The important role of metal surface treatment in anti-corrosion coating

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This post was last edited by Wang Wei2 on 2023-9-5 at 12:14. The important role of metal surface treatment in anti-corrosion coating: For most anti-corrosion coatings, it is necessary for the metal surface to have a certain level of cleanliness and roughness; otherwise, the surface does not meet the required standards, the quality of the coating applied becomes inadequate, and the anti-corrosion layer fails prematurely. Surface treatment can create conditions for high-performance coatings in two aspects: one is mechanical, by providing surface roughness to the coating ； The second aspect is chemical; it ensures close contact between the molecules of the coating and the surface of the steel substrate. Its main functions are as follows: 1. Overcoming the adverse effect of smooth surfaces on coatings. Since metal surfaces are very smooth, there is no good adhesion between the coating and the surface; it is therefore possible to remove the coating from the glass surface easily using a scraper or even fingernails. On the contrary, the metal surface is as rough as sandpaper, so it is not easy to remove the coating. The reason is that after sandblasting the steel surface, it becomes as rough as sandpaper, with numerous tiny peaks and valleys (surface roughness). The coating extends to the bottom of the wave troughs, with the wave crests acting like teeth that firmly grip the coating. Surface roughness can be described as “anchors” or “mechanical teeth”. It increases the contact area between the surface and the paint coating. 2. Eliminating the harmful effects of surface contaminants on the coating: Contaminants on metal surfaces are composed of various substances, including dirt, dust, grease, oil, rust, oxide scales, and sometimes water vapor as well. When dirt covers the coating, its mechanical and chemical adhesion are affected, and the coating fails. On the contrary, if these contaminants are removed before painting, a complete coating that bonds well to the steel is formed on the metal surface, thereby ensuring effective adhesion of the coating. 3. Harmful substances invisible to the naked eye: There are some chemical hazards that cannot be seen with the naked eye. The most harmful chemical pollutants are certain soluble salts, such as chlorides and sulfides, etc. If these harmful substances are not completely removed, they will allow water vapor to penetrate the coating and reach its bottom, causing bubbling and separating the coating from the substrate, which in turn accelerates the corrosion of the steel.