Powder coating is a method of adding colour and protection to metal that has far greater staying power than paint. Rather than liquid paint, a dry powder is sprayed on to metal using compressed air and an electrostatic gun. The powder sticks to the surface of the metal because of an electrical charge. The new coating is then cured (or baked) using high heat in a specialist oven, or UV lamps, to make it stay in place.
What metals can be powder coated?
Aluminium, stainless steel, galvanised steel and most steel alloys can be powder coated. Plenty of other materials can be coloured in this way too, including glass, wood, MDF and certain types of plastics.
What kind of products are powder coated?
Powder coating is an effective way to colour and protect a huge range of everyday parts and products. Some examples include household appliances, furniture, metal garden products, bicycles, industrial components, wheel trims and other car parts,
What is the powder made of?
Powder coating comes in many different forms, usually different kinds of plastic or epoxy resins. There are two main categories of plastic coating, though: thermoplastics and thermosets.
Thermoplastics are ductile, meaning they can be easily manipulated. Even when a thermoplastic has been cured, it can be reset again and again, a useful quality for correcting mistakes or making changes. Their ductility means that thermoplastics are less brittle than thermosets (more on those next), and are therefore less likely to crack. Polyester, nylon, Teflon and PVC are all thermoplastics.
The other common type of material used in powder coating is thermosets. During the curing process, polymers in the molecular structure form unbreakable cross links, making the coating irreversible. There’s no room for mistakes here, but the advantage is that thermosets can be used in applications where there are high levels of heat because the coating will not melt. What’s more, thermosets tend to be cheaper than thermoplastics. Examples of thermosets are silicone, epoxy and polyurethane.
An easy way to remember the difference between the two types of powder coating material is that the word ‘thermoset’ includes the word ‘set’, and this sort of powder coating sets permanently.
Why powder coat?
There are many reasons why powder coating metal is a good thing. Here are just a few:
- It’s quick. Unlike paint, you don’t have to wait around for powder coating to dry. Some people powder coat without a primer, too, although using a primer does help powder coating last even longer.
- It’s durable and has a long lifespan. Powder coating protects metal from rusting and lasts a long time. It won’t crack like paint, and although it will fade in the sun eventually, special UV coatings can help the colours stay vivid for longer.
- It’s economical. Although powder coating might initially cost more than painting, it lasts longer and is much lower-maintenance, so in the long run, it usually works out cheaper than paint.
- It’s eco-friendly. Because an electrical current makes the powder stick to the metal, rather than harsh chemicals, this method is much better for the planet than traditional painting. Paints often contain volatile organic compounds (VOC) which can cause pollution and are harmful to the environment.
The downsides
There are plenty of benefits to powder coating, but not every process suits every application. Naturally, there are some negatives to powder coating.
- It’s more expensive in the short-term. Powder coating requires specialist machinery and materials which make it more expensive than painting. As we mentioned earlier, it usually works out cheaper in the long run, but the initial outlay needs to be taken into consideration.
- The finish can be uneven. With powder coating, it is harder to create the smooth surface that you get with painting. In some cases, a powder-coated finish can be imperfect. When this happens, it is known in the industry as ‘orange peel’ because the tiny indentations resemble those on the skin of an orange. Depending on the product in question, this could be an issue.
- Inability to mix colours. Everyone knows you can mix paints to create exactly the shade you’re looking for, but this can’t be done with dry powder. There are, however, a huge number of powder colours on the market, so as long as precisely the right shade is chosen, this shouldn’t be an issue.
How long does powder coating last?
Although powder coating is known for its longevity, it doesn’t last forever. There are a number of factors that can affect how long the coating lasts, including how well the surface is primed before it is sprayed, the material being coated, the formula of the powder itself and unpredictable weather. As a general guide, most powder coating should last for between 15 and 20 years.
