Surface treatment includes three basic tasks: ①structural treatment; ②surface cleaning; ③surface roughness.
Before further surface treatment, the steel itself needs certain structural treatment, such as grinding of sharp edges, rounding of chamfers, removal of spatter, repair welding and grinding of welding holes. Since solvent-based coatings have a tendency to shrink on sharp edges, the surface coatings on sharp corners, sharp edges, uneven welds, etc. will be much thinner than flat surfaces, or even have no coating coverage. These problems have a great impact on the integrity and adhesion of the coating. big impact. Likewise, undercuts or weld holes that are too deep, the paint cannot penetrate effectively, leaving voids that leave weak spots for future corrosion. Therefore, the structure of the steel itself needs to be treated before rust removal to facilitate the integrity of the coating.
If it is concrete, before cleaning the surface, it also needs to be treated on the surface structure, such as filling of holes and cracks, treatment of hollowing, etc.
Surface cleaning refers to the removal of substances on the surface that are harmful to the coating, especially scale, rust, soluble salts, grease, moisture, etc. If the surface cleaning is not effective, impurities and dirt will remain, which will affect the protective effect of the coating.
Surface roughness can increase the contact surface to the coating, and has a mechanical anastomosis effect, which improves the adhesion of the coating to the substrate. Roughness requirements for anti-corrosion coatings are usually Rz 40~7 5µ.m. The roughness should not be too large, otherwise it will often cause insufficient thickness at the wave crest, causing early pitting corrosion. Moreover, air bubbles are trapped in the deep pits, which become the source of coating bubbling.
