3.Powder coating – Painting parts
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Powder coating is a method of obtaining polymeric coatings with high protective and decorative properties. The method of powder coating is an alternative to applying liquid coatings for parts, car parts, allowing heat treatment.
The main steps of powder coating technology:
- Degreasing and removal of dirt from the surface of painted products;
* Cleaning parts with a shot or sand.
* Surface preparation unit for purification of fraction, sand, oil deposits.
* Iron or zinc phosphating (depending on the type of metal).
* High temperature drying >220 °C
that is, similarly to the preparation of the surface of the body.
- The process of spraying powder paint on the product is by electrostatic spraying. An electrostatic charged powder is fed to the grounded product with the help of a spray gun, the process is similar to the industrial painting of products for cars.
- Painters should be provided with special antistatic PPE with the supply of specially prepared breathing air.
Air conditioning equipment is expensive.
- The final stage of painting takes place in the furnace melting and polymerization. The paint is melted and polymerized at a metal temperature of 180-220 °C for 20-30 minutes.
- Best performance characteristic, high quality coatings;
- No need for priming the surface;
- Powder paints have the best impact and corrosion resistant properties;
- Less porosity in powder coating;
- The paint is delivered ready-made, it does not require special preparation and viscosity control;
- High strength of powder paints during transportation ensures minimal damage to painted surfaces, which ensures cost reduction.
- Loss in powder painting about 2-5%, when painting with liquid paints, the losses will be up to 45%;
- Control adherence to temperature conditions in painting booth;
- For prevent the explosion(fire) requires control of painting process;
- The impossibility of painting the interior and hidden cavities.
Leader supply of equipment its company Nordson (Encore)
Suppliers of powder coating are both Russian and another country. Main criteria price, physical and mechanical properties in operation of finished product, visual appearance.
The most mistake in use of powder coating is the absence or substandard quality surface preparation before application and painting on the “bare” metal, without primer, as well as non-compliance with temperature regimes during powder polymerization.
Painted powder coating plates are not professional (front side)
- Result after 500 hours of saline mist camera (Left)
- Before chamber of a salt fog (To the right)
Conclusion: after 500 hours in a saline mist chamber at 95% humidity and 5% NACl solution, the powdered powder sample partially began to break down and peel off in separate small “pieces”, which indicates that the adhesion between the polymer and the metal was broken, and it is also likely samples are painted with a violation of technology.