There are many differences in the processes between powder coating lines and paint coating lines. The following is a detailed introduction:

Properties of Coatings and Pretreatment

Powder Coatings: Powder coatings exist in the form of solid powder and do not contain organic solvents. Their main components include resins, pigments, fillers, curing agents and other additives. Before coating, it is necessary to carry out pretreatment such as degreasing, derusting and phosphating on workpieces to enhance the adhesion of powder coatings to the workpiece surfaces.

Paint Coatings: Paint coatings usually exist in a liquid form and generally consist of film-forming substances, solvents, pigments and additives. Its pretreatment process is similar to that of powder coatings. However, since the solvents in paint may have an impact on certain pretreatment layers, more caution is required when selecting pretreatment methods and materials.

Coating Equipment and Operation

Powder Coating: Electrostatic powder spraying equipment is mainly used, which utilizes the principle of electrostatic adsorption to make the powder coatings evenly adhere to the workpiece surfaces. During operation, parameters such as the voltage, current, powder spraying amount and the distance between the spray gun and the workpiece need to be adjusted properly to ensure the uniformity and thickness of the coating. In addition, the recovery system is also an important part of the powder coating equipment, which can recycle and reuse the powder that has not adhered.

Paint Coating: There are many types of paint coating equipment, commonly including air spraying, airless spraying, electrostatic spraying, etc. Air spraying equipment is simple and easy to operate, but the utilization rate of coatings is relatively low. Airless spraying can achieve higher coating efficiency and thicker coatings, but it has higher requirements for equipment maintenance. Electrostatic spraying can improve the utilization rate of coatings and the uniformity of coatings. When operating paint coating equipment, parameters such as the pressure, flow rate and nozzle diameter of the spray gun need to be adjusted according to the characteristics of the paint and the requirements of the workpiece.

Drying and Curing Methods

Powder Coating Lines: The curing of powder coatings usually needs to be carried out at a relatively high temperature, generally between 180 °C and 220 °C. Through heating, components such as resins in the powder coatings undergo cross-linking reactions to form a firm coating. The curing time is usually about 10 to 30 minutes, depending specifically on the types of powder coatings and the coating thickness.

Paint Coating Lines: There are various drying methods for paint, such as natural drying, low-temperature baking and high-temperature baking. Natural drying is suitable for some paints with a slow drying speed. The solvents in the paint are allowed to evaporate at room temperature to make the coating cured. Low-temperature baking is generally around 60 °C to 80 °C and is suitable for some workpieces and paint varieties that are sensitive to temperature. High-temperature baking is above 100 °C, which can accelerate the drying speed of the paint and improve the performance of the coating. However, attention should be paid to controlling the temperature and time to avoid workpiece deformation or coating quality problems.

Coating Quality and Performance

Powder Coating Lines: Powder coatings have relatively high hardness, wear resistance and corrosion resistance. The coating thickness is generally between 50 μm and 150 μm and can be controlled by adjusting the powder spraying amount and the number of spraying times. The appearance of powder coatings is usually relatively flat and smooth, but the coating thickness may be uneven on some workpieces with complex shapes.

Paint Coating: Paint coatings have better flexibility and can better adapt to the deformation of workpieces. For some workpieces that need to be bent or stretched frequently, paint coatings have better adhesion and anti-cracking properties. The appearance quality of paint coatings can reach a high level through fine operation and adjustment, and can achieve various requirements for colors and glossiness. However, they may be slightly inferior to powder coatings in terms of hardness and wear resistance.

China Hengjiu Jinye focuses on the development, design, planning, production, sales and installation of turnkey projects for powder and liquid coating lines.