With the rapid development of the coating industry, domestic coating technology and process management have received increasing attention and made great progress. The painting process generally consists of several main processes, and the number of processes depends on the decorative and functional properties of the coating. For high demand applications, there can be dozens or even hundreds of processes. However, in terms of the content and essence of the processes, the painting process is composed of three basic processes: pre-treatment, coating and drying, as well as several auxiliary processes.

1. Remove burrs and debris such as floating rust from the surface of the substrate;

2. Eliminate particles, roughness, and unevenness on the coated surface of the workpiece. For example, the surface scraped with putty is generally rough and uneven after drying, and needs to be polished to obtain a smooth surface;

3. Enhance the adhesion of the coating. The adhesion of coatings on smooth surfaces is poor, and polishing can enhance the mechanical adhesion of coatings. Therefore, polishing is one of the important operations to improve the coating effect.

Coarse or fine sandpaper, woodworking sandpaper, etc. are generally used to polish the surface of the substrate. The putty layer for polishing and filling pits is generally made of fine sandpaper or grinding stone. Sandcloth and woodworking sandpaper are only suitable for dry polishing. When applying coatings and topcoats during wet polishing, use water-resistant sandpaper (water sandpaper). According to the abrasive particle size of water-resistant sandpaper, there are several numbers, and the higher the number, the smaller the abrasive particle size and the finer the sandpaper.

1. The selection of polishing materials should be strictly in accordance with the process requirements, and 80 # to 120 # sandpaper should be used for dry polishing putty; Use 240 #~320 # water sandpaper for wet polishing of intermediate coatings; Wet polishing topcoat coating should use 360 #, 400 #~600 # water sandpaper, and there should be no residue of sandpaper marks. At the same time, the quality of the water-resistant sandpaper should be checked before polishing, and there should be no mechanical impurities (coarse sand particles) to prevent scratching the coating. When using water-resistant sandpaper, it should be moistened with water before being torn or folded for use;

2. Attention should be paid to directionality during polishing, and it is not advisable to grind randomly in all directions. When polishing, it is not advisable to press too tightly. To improve the flatness of the polished surface, cork or rubber grinding blocks can be placed on the sandpaper during manual polishing. Cork grinding blocks are suitable for sanding putty in intermediate coating applications; Rubber grinding blocks are suitable for intermediate or topcoat applications;

3. During the polishing process, the polishing ash should be continuously removed. After wet polishing, it should be rinsed clean with deionized water, blown dry, and the coated surface should be dried;

4. The coating should be completely dry before polishing, otherwise sandpaper will stick during polishing, which will affect the polishing quality.