Powder coating is an alternative to painting in which powdered, pigmented particles are given an electrostatic charge and sprayed over a grounded item using a special gun; the powder is then cured using heat. The two main types of powder used in powder coating are thermoplastic powders and thermosetting powders. Thermoplastic powders can be melted when reheated, whereas thermosetting powders can't be melted again once they're cured. In traditional wet painting, the coating "cures" as the liquid part of the paint evaporates. Since there's no liquid involved in a powder coating, it's considered dry paint. For these reasons, powder coating is also referred to as electrostatic powder painting and non-solvent painting.
The curing process for powder coating is normally done in a special oven; the coating has to be exposed to a temperature range of 350 to 400 degrees Fahrenheit (160 to 210 degrees Celsius) for 20 minutes. When melting the more common thermosetting powder, it bonds chemically to form a hard, permanent layer of paint. Thermoplastic powders harden, but if they are heated again, they become malleable and only harden again when they cool.
To cure powder coating, both the powder and the substrate have to reach the desired temperature and stay there for the allotted time without any temperature fluctuations. For this reason, the best way to cure powder coating is with a curing oven. However, a kitchen oven works just as well, as long as you don't plan to use it for cooking food ever again. For small items, a toaster oven is just as good. While some people may choose to use a heat gun to melt the powder so that it stays in place while the item is transferred to an oven, a heat gun can't produce the necessary stable, all-encompassing temperature required to cure powder coating.
Originally Published: Apr 27, 2011