Powder coating is a dry finishing process that has become extremely popular since its introduction in North America over in the 1960s. Representing over 15% of the total industrial finishing market, powder is used on a wide array of products. More and more companies specify powder coatings for a high-quality, durable finish, allowing for maximized production, improved efficiencies, and simplified environmental compliance. Used as functional (protective) and decorative finishes, powder coatings are available in an almost limitless range of colours and textures, and technological advancements have resulted in excellent performance properties.
Powder coating is applied as a free-flowing powder in a completely dry form. Think of it as paint with the solvent part removed. The coating is applied electrostatically and then cured under heat which causes it to form a kind of “skin.” Usually powder is used to coat metals, but there are a number of potential applications.
Powder coatings are based on polymer resin systems, combined with curatives, pigments, levelling agents, flow modifiers, and other additives. These ingredients are melt mixed, cooled, and ground into a uniform powder similar to baking flour. A process called electrostatic spray deposition (ESD) is typically used to achieve the application of the powder coating to a metal substrate. This application method uses a spray gun, which applies an electrostatic charge to the powder particles, which are then attracted to the grounded part. After application of the powder coating, the parts enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density. These molecular chains are very resistant to breakdown. This type of application is the most common method of applying powders. Powder coatings can also be applied to non-metallic substrates such as plastics and medium density fibreboard (MDF).
Sometimes a powder coating is applied during a fluidized bed application. Preheated parts are dipped in a hopper of fluidizing powder and the coating melts, and flows out on the part. Post cure may be needed depending on the mass and temperature of the part and the type of powder used. No matter which application process is utilized, powder coatings are easy to use, environmentally friendly, cost effective, and tough!
When cured, powder coating forms a protective finish that is much harder than conventional paint. However, that does not necessarily mean powder coating is the most durable solution on the market. Depending on the application, alternatives may prove to offer a longer-lasting finish. Powder Coating gives consumers, businesses, and industries one of the most economical, longest lasting, and most colour-durable quality finishes available on virtually any type of metal. Powder coated surfaces are more resistant to chipping, scratching, fading, and wearing than other finishes. Colour selection is virtually unlimited with flat, satin, gloss, high gloss, metallic, candies, clear, iridescent, fluorescent, wrinkle, hammer tone, and glitter finishes available. Colours stay bright and vibrant longer. Texture selections range from smooth surfaces to wrinkled or matte finishes, and rough textures designed for hiding surface imperfections.
The powder that does not adhere to the surface being coated is collected and reused, meaning that there is little waste. And since the coating process happens in a sealed environment, there is little to no risk of air pollution. This is an advantage to be sure, but changes in industry standard mean that most contemporary coating process operate in a sustainable way. While liquid finishes contain solvents which have pollutants known as volatile organic compounds (VOC's), powder coating contains no solvents and release negligible amounts, if any, VOC's into the atmosphere. Therefore, there is no longer a need for finishers to buy and maintain costly pollution control equipment.
As noted above, this process produces very little waste. There can be significant attendant costs related to the heating/curing process though. Elimination of VOC's and the reduction of waste saves money and helps companies comply more easily and economically with the regulations of the U.S. Department of Environmental Protection Agency. In fact, one of the major elements in expanding the market for powder coating has been the implementation of stringent air pollution control legislation over the past thirty years.