What is powder coating?
Powder coating is a type of coating that is applied to the surface of the workpiece in the form of dry powder and then cured at high temperatures. The powder can be a thermoplastic or a thermosetting polymer. It is often used to create a harder surface than traditional liquid coatings and can be used on plastic, glass or metal surfaces.
Functions
Make the surface of the product smooth and uniform color with strong acid resistance, alkali resistance, collision resistance, wear resistance can withstand the erosion of strong ultraviolet radiation and acid rain for a long time without coating powder, fading, falling off and other phenomena.
Powder coating advantages
- High efficiency: due to one-time film formation, productivity can be increased by 30-40%.
- Energy saving: reduce energy consumption by about 30%.
- Less pollution: no organic solvent volatilization (does not contain toluene, xylene and other harmful gases in paint coatings)
- The paint utilization rate is high: up to 95%, and the powder can be used many times after recovery.
- Good film performance: one-time film thickness up to 50-80um, its adhesion, corrosion resistance and other comprehensive indicators are better than the paint process 6, high yield: before curing, can be resprayed twice.
It has three categories: thermoplastic powder coatings (PE) thermosetting powder coatings, architectural powder coatings.
Two common electrostatic powder spraying and dipping.
Electrostatic spraying
The coating sprayed out by the electrostatic powder spray gun makes the powder particles negatively charged while dispersing, and the charged powder particles are coated to the grounded coating under the action of air flow (or other forces such as centrifugal force) and electrostatic gravity, and then heated and melted to form a film.
Powder impregnation
It is often used for coating metal surfaces such as bicycle baskets and railway mesh fences, which are characterized by a strong and hard powder coating.
Liquid dipping process
preheating, dipping, plasticizing, cooling, stripping five processes, and then through product post-treatment (tail cutting) into finished products, and finally packaging, shipping.
The advantages and disadvantages of powder uncoated treatment
Advantages
- Durability: Durability is a key advantage of non-coated parts, and most non-coated materials are resistant to fading, cracking, scratching and wear.
- High-quality surface coating: The high-quality elements produced by powder coating treatment have a clean surface, and the physical strength, wear resistance and other properties of the product have been improved.
- Environmentally friendly: it contains volatile organic compounds, so there are no harmful chemicals and solvents in various forms. In addition, the powder is not coated on the surface and then cured under heat, and the excess powder is not recycled, so the process produces very little waste.
Disadvantages
- High initial cost
- Powder can not be mixed
- Difficult to repair
Use of powder spray gun
- Point the powder spray gun at the powder spray chamber and pull the trigger to test spray the workpiece.
- Adjust electrostatic high voltage, electrostatic current, velocity pressure and physical and chemical pressure.
(a). Electrostatic high voltage 60-90kV. High voltage is easy to cause powder rebound and edge pitting; If the voltage is too low, the powder rate is low.
(b). Electrostatic current 10-20uA. High current is easy to produce discharge breakdown powder coating. Too low current will also cause low powder rate.
(c). Flow pressure 0.30-0.55MPa. The higher the flow pressure, the faster the deposition rate of the powder, which is conducive to quickly obtaining the required coating thickness, but if it is too high, the amount of powder and the loss rate of the powder spray gun will be increased
(d). Atomization pressure 0.30-0.45MPa. Increasing the cloud pressure properly can keep the thickness of the powder coating uniform, but too high will cause the powder feeding parts to wear quickly. Proper reduction of atomization pressure can improve the powder covering capacity, but too low is easy to clog the powder feeding parts. Therefore, it is necessary to properly adjust the spraying parameters of the powder spray gun, which can improve the efficiency of powder, maintain the spraying effect and ensure the use of the powder spray gun Life span.
Control spraying distance and spraying stroke
- When spraying, the distance between the workpiece and the nozzle should be maintained between 150-300mm. If the distance between the workpiece is too close, it is easy to short-circuit and spark, resulting in a breakdown point on the coating surface, affecting the coating effect.
- When spraying, be sure to keep the gun perpendicular to the workpiece plane, otherwise it will cause paint waste.
