What are the auxiliary processes in the painting process?

What are the auxiliary processes in the painting process?

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.

The auxiliary process is not an essential part of the coating process, but rather a coating process that serves as an auxiliary to the main process or meets the special requirements of a certain product. It includes processes such as polishing, waxing, waxing, applying car bottom paint, sealing, etc. Because they are auxiliary processes, many manufacturers have not given sufficient recognition and attention to these processes.

polish

Polishing is divided into dry polishing and wet polishing. Dry polishing does not require water to moisten, while wet polishing lubricates the coating with water or other wetting agents to obtain a smoother surface and remove grinding dust. For example, when polishing nitrocellulose paint and perchloroethylene paint, not only wet them with water, but also with pine perfume. In order to improve the decoration of the finish paint, it can be polished with very fine water sandpaper before polishing, or soapy water can be used as a wetting agent. The main purpose of polishing is to:

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.

When polishing, the main things to pay attention to are:

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.

Because polishing is usually done manually, sometimes with the help of pneumatic tools or some simple equipment, the labor intensity of polishing is high, and efforts are being made to eliminate this work in industrial coating production.