The most common uses for powder coating are to provide finishes for metallic surfaces and products.
This versatile method has a broad range of applications across different sectors and industries.
It is a dry coating process, using specialist coating materials. These materials are a mixture of polymer, resin, pigment, curatives and other agents.
How does powder coating work, and what are the benefits of using it?
What is Powder Coating?
Powder coating consists of various resins and pigments, ground down into a powder, which is then melted and re-ground to blend the ingredients together.
Powder coating has two main categories:
Thermoplastic
Thermoset.
Thermoplastic powder coatings include polyester, PVC, polyolefin and nylon powder coatings. These kinds of powder coating offer good protection from wear and tear and can provide resistance to chemicals. They are, however, less heat resistant than thermoset powder coatings.
Thermoset powder coatings include acrylic, epoxy, epoxy-polyester hybrids and silicon. They have a good heat-resistance, with some withstanding temperatures exceeding 500°C. They are good electrical insulators, but can become brittle if they have prolonged exposure to UV light.
The major difference between thermoplastic and thermoset powder coatings is that thermoset coatings generally set much harder after curing, and undergo an irreversible process due to their chemical reaction under heat.
Different powder coatings are more suitable to different applications. If you wish to apply one, it therefore makes sense to talk to a powder coating expert first.
What is the Powder Coating Process?
Powder coating is a dry coating process, very different to applying liquid paint finishes.
Essentially, it is paint without its liquid carrier, but with other ingredients that make it act in a certain way during curing and finishing.
To apply powder coating to a surface or object, you spray it. This is with an electrostatic gun.
This device charges the particles it sprays electrostatically, which causes them to adhere to the surface you are applying them to.
The principle behind this is the law of attraction between positively and negatively charged particles.
Compressed air in the spray gun forces the powder coating through the nozzle, atomising it into a fine spray. This atomisation process charges the powder particles positively in a static field.
The substrate you are applying the powder coating to is negatively-charged.
The positive charge to the powder counters the effects of gravity once you spray it into the air, causing it to adhere to the substrate surface, coating it completely.
Once the surface is coated, it is ready for curing and finishing.
This involves the application of heat, which will cross-link the structures in the powder coating, causing them to melt together and bond.
The film surface this creates will then harden.
Curing takes place in a special oven.
Once cured, the coated surfaces must be left to cool.
Typically, the entire powder coating process is rapid, and with a coating that is tolerant of high temperatures, curing can take as little as 30 minutes.
What are the Benefits of Powder Coating?
Powder coating is a versatile way of providing both protective and decorative coatings to mainly metallic surfaces, fabrications and items.
It is tough and long-lasting, and provides an even finish. Because you apply it as a dry powder, it can reach and coat difficult-to-reach areas and angular constructions.
There is no solvent content to powder coating, which means it requires far less air control during its application and it is a relatively clean technique.
It has good environmental credentials, as it contains no volatile organic compounds (VOCs), which can form pollutants in the air. It is easy to transport and to dispose of safely.
It is also cost-effective because any over or under-used powder you can collect and re-use.
The whole process is a streamlined one, which maximises efficiency but ensures durable, professional finishing.
Why Choose Powder Coating?
Many metals require surface finishes to give them resilience, and to make them more attractive.
Powder coating is applied to agricultural machinery, architectural parts and industrial components.
You also find it on consumer items such as garden furniture, office furniture and golf carts. Powder coating is the preferred choice for many outdoor surfaces and products.
It combines high performance with good colour retention, and you can have a range of finishes, from smoother to more textured surfaces.
