Thermosetting powder coatings are applied using high-voltage, low-current electrostatic spraying technology. Manual spray guns or automatic coating lines composed of multiple spray guns can be used for spraying. The friction powder spray gun that works on the principle of friction charging is not effective for all types of powder coatings. When using this type of spray gun, attention should be paid to the choice of powder coating types.
Before the sprayed workpiece enters the drying tunnel or oven, the sprayed workpiece should be carefully inspected, and the thin and damaged parts should be sprayed or repaired completely. When repairing is impossible, the powder on the workpiece can be removed with compressed air and then sprayed again. Compared with ordinary paint, this process can correct defects in the construction process in the early stage of construction. Therefore, the scrap rate of powder coatings is extremely low.
The sprayed workpiece is directly sent to the drying tunnel or oven (no open flame), and the powder coating is melted, leveled, and cured into a coating film at the temperature required by the process. The general curing condition is that the workpiece temperature is baked at 180°C for 10-15 minutes (of course, the time for the workpiece to rise from room temperature to this temperature must be considered, that is, the size and heat capacity of the workpiece).
As long as the curing process conditions of powder coatings are strictly followed, high-performance coatings can generally be guaranteed in most cases. For high-quality powder coatings, a certain limit of over-baking is allowed without affecting the performance of the coating.
The curing tunnel and the electrical equipment of the oven should be checked regularly and repaired in time to ensure that the required conditions are fixed.
In order to ensure high-quality coating, strict implementation during construction:
1. The powder coating should be stored in a cool and dry sealed condition, and used strictly in batch order.
2. Before spraying the workpiece, all oil and pollutants on the surface should be thoroughly removed, and the workpiece should be treated correctly.
3. The compressed air should be oil-free, water-free and dry. Check the working condition of the oil-water separator frequently.
4. The structure design of the workpiece holder should be reasonable, and it should maintain a good connection with the ground transmission part. Fixtures should be cleaned regularly to maintain good grounding.
5. Correctly select the powder coating required for the final coating
6. The performance of the temperature control system of the oven should be stable and it should be able to ensure the conditions required for curing the coating.
7. The powder feeder, recovery system and spray cabinet should be free of pollution and no other powders should be mixed, otherwise it will affect the appearance of the final coating.
8. Frequently check the performance of the pretreatment and curing furnace, and check the physical properties of the powder used.
9. The recycled powder must be sieved and mixed with new powder in the specified proportion.
10. Avoid silicon dust or paint dust near the powder coating spraying site, so as not to affect the appearance quality.