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Auto Tech: Powder coating finishes

June 17, 2009

Another difference I see in some shops is that many shops will spray the powder on a cold part, while other shops heat the metal in the oven before spraying the powder on. There is an advantage to preheating the metal, as it enables a thicker layer of powder to be applied to the part, but there is the extra cost of running the oven longer.

The powder is applied using a spray gun and electrostatic charge. In the powder coating booth, every part is connected electrically to the powder coating machine, which creates a charge on the part. The powder is charged with an opposite polarity, so when it is sprayed out of the gun with air pressure, it is attracted to the metal part. Once the part is covered, it is moved into the oven to bake for several minutes until the metal is hot and the powder melts and flows out in a smooth finish over the part.

Many of the cosmetic finishes use a polyester powder. When powder coating first became common, there were maybe two or three dozen colours available. Today, the sky is the limit, with metallics, metal flake, pearlescent and hammertone finishes available in a wide variety of colours. Of course, the more uncommon the finish, the higher the cost to have it done, but if you want something unusual, it is possible.

There are economical powder coating kits available so you can do it at home, but don’t do it in your kitchen. Buy an oven for the garage. I find it easier and cheaper to take it to a custom powder coating company – there are many around – who can do a superior job. Some have ovens capable of baking a complete metal truck box or a car frame! Common colours such as black or red may be sprayed often but if you want something unique, you may have to wait longer and pay for the extra time to clean the powder spraying equipment each time a colour is changed. This isn’t a big deal if you have a large number of parts to spray, but can be expensive if you want one or two small parts done.

Powder coated finishes look great, although they can’t compare to paint when it comes to mirror-like finishes. They are extremely durable and can withstand bumps, knocks and blows that would destroy paint. Car enthusiasts like powder coating for finishing suspension parts, but with a little imagination, almost anything metal can be powder coated.

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