Since its initial conceptualization during the 1940s, powder coatings have steadily grown in popularity and usage primarily in industrial manufacturing processes.
That being the case, powder coating technology has remained unfamiliar to a large portion of the general population even if they encounter powder coated products every day without even knowing it.
Here, we explain the basics of powder coating technology, the different types of powder coatings, its benefits and limitations, and where you can find it.
In technical terms, powder coating is a dry coating or finishing process where a dry powder paint is applied to a surface, melted, and then hardens to form a protective coating.
Put more simply, it is a way to coat something with colored, non-wet powder paint. You can imagine powder paint to have the consistency of baby powder, but available in colors other than white.
When heated on the product to be coated, the powder paint melts into a fluid, and then hardens, forming an even layer over the product surface, effectively protecting whatever is beneath it.
Powder coating technology can be used on a variety of surfaces like metals, plastics, glass, and engineered fiberboards, but is most commonly used to coat metal products.
Powder coatings or powder paints can be classified as either thermoplastic or thermoset, with each having very different properties, advantages and disadvantages, and applications.
Thermoplastic powder coatings are characterized based on how the powder particles react to heat. When heated, thermoplastics become softer and start acting more fluid-like. When cooled, thermoplastics return to their original state, regaining their solid properties, but are now in the same shape they were last left.
To make it easier to imagine, you can think of thermoplastic powders like cheese or chocolate, initially solid but melts upon heating, and eventually returning to solid form when cooled, often in the shape of its container or as a shell covering something beneath it.
Thermoplastic powder coatings do not chemically change when moving from solid to liquid and back, making the thermoplastic powder coating process reversible, just by remelting and removing the coating.
Thermoset powder coatings similarly require heat to be applied, but crucially, change their chemical structure when heated. Thermoset powders react this way because they are formulated with an ingredient, called a cross-linking agent, that forms chemical bonds when cured, creating a non-reversible surface coating.
Another way to imagine thermoset powder coatings would be to imagine them like cookie dough or cake batter – you need to bake them to be able to eat them, but once they’re baked, it becomes impossible to revert back to cookie dough or cake batter.
Due to this irreversible curing process, thermoset powder coatings cannot be remelted, and are often preferred for high-temperature applications and environments. In addition, you have a much thinner coating thickness for thermoset powder coatings versus thermoplastic powders.
Increased durability - Powder coatings offer better impact, moisture and chemical resistance, and hold up better against abrasion, scratches, and general wear & tear when compared to traditional liquid paints.
Environmentally friendly - Powder paints contain no harmful solvents, produce significantly less hazardous waste, and are either formulated to be VOC-free or Low-VOC products, making it more friendly to the environment and to those handling it when compared to liquid coatings.
Increased process savings - Powder overspray can be gathered and recycled, resulting in higher material utilization and lower material cost. In addition, powder coating processes enjoy faster turnaround with the ability to handle, pack and transport right after cooling.
Versatile finishing options - Aside from the usual gloss, semi-gloss, and matte options, powder coatings are also available in specialized textured, wrinkled, and antique finishes, which are sometimes unavailable with liquid paints.
Increased equipment cost - The initial investment required to set up one's own powder coating line tends to be higher than that of a liquid coating line, given the steeper cost of equipment such as electrostatic spray guns, spray booths, powder recovery systems, and curing ovens.
Limited finish flow-out - Given a liquid coating's inherent fluid-like properties, powder coatings often struggle to match the flow-out or "smoothness" of a liquid paint finish.
Home appliances - Powder coatings are the preferred coating method for appliances given their thin and even coatings, but more importantly, due to their excellent durability and resistance to household cleaning detergents & chemicals.
Applications include refrigerators, washers & dryers, outdoor air conditioner units, and electric fans & fan guards.
Aluminum extrusions - Architectural component manufacturers choose powder coatings for use on their windows and doorframe products for their increased durability and resistance to sun exposure & weathering. Buildings and structures are usually built to last lifetimes - their coatings need to last just as long.
Outdoor furniture & equipment - With sun exposure & rain causing long-term corrosion & fading concerns, powder coatings have become the popular coating method for outdoor metal products because of their UV & weather protection and resistance to moisture, salt water & fertilizer.
Applications include patio furniture, tractors & farm equipment, push carts, and golf carts.
Office equipment & cabinetry - Powder coating office furniture and equipment has become the norm in recent years due to their long term durability. You can find them being used to coat filing cabinets, safety or security boxes, computer cabinets and desks.
High usage parts - With its superb durability and resistance to abrasion, chipping and cracking, powder coating is usually used on high usage parts to ensure longevity.
Applications include door knobs and handles, window handles, and some car parts such as bumpers and wheel mags.
Given the complexity of powder coating technologies, it's easy to see why fewer people are familiar with the powder coating process when compared to liquid paints. Nevertheless, powder coating technology has numerous benefits over traditional liquid paints, and has found its place and is often the preferred process for numerous applications.
With a basic understanding of powder coatings, you can now decide if they are suitable for your products and see if you can take advantage of for your own manufacturing processes.
