Powder spraying is a coating process that uses powder spraying equipment such as electrostatic spraying machines to spray powder onto the surface of workpieces, and the powder is adsorbed onto the surface of the workpiece under the action of static electricity. After high-temperature baking, leveling, and curing, many different types of final coatings will appear.

Process flow:

Loading → electrostatic precipitator → spraying → low-temperature leveling → baking

Technical features:

Advantage:

1. Rich colors. High gloss and matte finishes are optional.

2. Low cost. Powder coating is suitable for the shells of building and furniture products, as well as radiators.

3. High utilization rate. The utilization rate of powder coating is 100%, environmentally friendly.

4. Strong defect coverage capability;

5. It can imitate the wood grain effect.

Powder spraying is the use of corona discharge phenomenon to adsorb powder coating onto the workpiece.

Firstly, the purpose of powder coating is to protect and extend the service life of the workpiece. The second purpose is decoration, making the appearance of the workpiece beautiful. The third is dedicated to special purposes and obtains special performance. Such as sound insulation, heat insulation, fire prevention, etc.

According to the purpose and requirements of painting, the paint coating consists of several layers. Such as primer, putty, and topcoat finishes.

Primer: It is the lowest layer of coating that comes into direct contact with the workpiece body. The function of the primer layer is to strengthen the adhesion between the coating and the workpiece body, and enhance the protective performance of the coating. Black metals should undergo phosphating treatment before painting, while non-ferrous metals should undergo oxidation treatment before painting.

Putty layer: suitable for rough and uneven car bodies. There are many drawbacks to using putty layers, such as construction difficulties and reduced adhesion between the coating and the workpiece body.

Topcoat layer: The main purpose of the topcoat layer is to increase the glossiness of the product and serve as the outermost layer of the coating.

Painting methods

There are many coating methods, mainly including brush coating, immersion coating, air spraying, high-pressure airless spraying, electrostatic spraying, and electrophoretic coating.

process flow

Principle of electrostatic spraying process

Powder coating is sprayed onto the surface of the workpiece through electrostatic spraying equipment, and then the powder is uniformly adsorbed on the surface of the workpiece under the action of static electricity to form powder coating. Powder coatings become different final coating effects after high-temperature baking, leveling, and curing. The spraying effect of powder spraying is superior to that of oil spraying in many aspects. Such as mechanical strength, adhesion, corrosion resistance, aging resistance, etc.

preprocessing

Protection, also known as covering or masking. If certain areas of the workpiece do not require painting, protective glue can be applied before preheating to prevent spray painting.

preheat. Generally, preheating is not required. If a thicker coating is required, the workpiece can be preheated to 100-160 ° C, which can increase the thickness of the coating.

spraying

The workpiece enters the powder spraying room and reaches the spray gun position through the conveyor chain, ready for spraying operation.

The electrostatic generator releases high-voltage static electricity (negative) towards the space in the direction of the workpiece through the electrode needle of the spray gun nozzle. High voltage static electricity ionizes (negatively charged) the mixture of powder and compressed air sprayed from the nozzle of the spray gun, as well as the air around the electrode. The workpiece is connected to the ground (grounding electrode) through a hanger and a conveyor belt, creating an electric field between the spray gun and the workpiece. The powder reaches the surface of the workpiece under the dual push of electric field force and compressed air pressure, and forms a uniform coating on the surface of the workpiece through electrostatic attraction.

Baking and curing

The sprayed workpiece is fed into the drying room through a conveyor chain and heated at 180-200 ℃ for a corresponding period of time (15-20 minutes) to melt, level, and solidify, thereby obtaining the desired surface effect of the workpiece. Different powders have different baking temperatures and times. This is something that should be noted during the curing process.

clean

After the coating is cured, remove the protective layer and smooth out the burrs.

check

For cured workpieces, daily inspections mainly focus on appearance (whether they are smooth and glossy, whether there are defects such as particles and shrinkage) and thickness (controlled within 55-90 μ m). Repair or re spray defective workpieces such as missed spraying, pinholes, protrusions, and bubbles detected.

packaging

After the inspection is completed, the finished products will be sorted and placed into transport vehicles and turnover boxes. They will be separated by soft packaging cushioning materials such as foam paper and bubble film to prevent scratches and abrasion. Packaging can be customized according to customer requirements.

Painting workshop

powder coating

Powder coated components

competitive advantage

1. Apply once to obtain a thicker coating. For example, for coatings with a thickness of 100-300 μ m, using ordinary solvent coatings requires approximately 4-6 times. But powder coating can achieve the required thickness at once. The corrosion resistance of powder coating is very good.

2. Powder coating does not contain solvents, and there is no pollution from the three wastes (wastewater, exhaust gas, and solids), which improves labor and hygiene conditions.

3. Adopting new technologies such as powder electrostatic spraying, it has high efficiency and is suitable for automated assembly line painting. The powder has a high utilization rate and can be recycled.

4. In addition to thermosetting epoxy resin, polyester, and acrylic, there are also a large number of thermoplastic oil resistant powder coatings. Such as polyethylene, polypropylene, polystyrene, fluorinated polyether, nylon, polycarbonate, and various fluororesins.

Powder coating has begun to be used for protection and electrical insulation. With the development of technology, it has been widely used for surface coating in the automotive industry, electrical insulation, corrosion-resistant chemical pumps, valves, cylinders, pipelines, outdoor steel components, steel furniture, castings, etc.