Compared to conventional liquid paint finishes, powder coating is generally more durable, eco-friendly, and cost-effective. Through a multi-step process, metal and non-metal parts are sprayed with a fine powder using either a spray gun or a spray booth. Before this begins, it is important to prepare the product for finishing. Below are the general steps to powder coating from start to finish:
Before the powder is applied, parts must be cleaned and/or pre-treated to prevent defects in the final finish. Dust, grease/oil, rust, and other contaminants need to be removed to ensure a smooth and even coat. Pretreatment processes can vary depending on the material being used and the part’s final application.
Electrostatic Deposition (ESD) - Finely ground particles of color pigments and resin (dry powder) are sent through a spray gun fitted with an electrode. This electrode provides an electrostatic charge to the dry powder as it is sprayed on the part. The grounded part attracts the charged particles, and they are held there until melted with the curing oven. A spray booth is typically used to help capture and reuse any overspray and to help contain the application process.
Fluidized bed powder coating is another common method of powder coating where pre-heated parts are dipped in a tank filled with a combination of powder material that has been fluidized. The bed is fluidized by adding compressed air at the bottom of the tank through a porous membrane.
ESD coated parts are cured differently than a fluidized bed method. For ESD, parts must be cured using a specialized powder curing oven. To reach the curing point, thermoset powders require thermal energy to melt the powder and create the chemical reaction over a specified length of time/temperature. Once the parts have been sprayed, they then need to be heated to a certain temperature and “cured” for a specific amount of time. The curing temperature and time are dependent upon part size and specifications.
Fluidized bed powder coated parts are heated prior to being dipped, which allows the curing to occur in the bed simultaneously. There also is the option to cure fluidized bed powder coated parts using the same method as ESD coated parts.
As technology continues to advance surrounding powder coating, this type of finish continues to be an economical way to provide durable, long-lasting parts. However, it is important to note, powder coating may not always be the best option for your parts.