What is Powder Coating?
Since the 1960s, powder coating has been a popular dry finishing process in North America. The powder coating process is very versatile, which makes it so popular. Because of its smooth finish, powder coating is both decorative and protective, making it extremely functional. It can also be used on a variety of surfaces, including metal, plastic, and even medium density fiberboard. Powder-coated surfaces become resistant to scratches, corrosion, and even many chemicals. Not only is it versatile, but the powder coating process is also cost-effective, and can help materials comply with environmental standards.
How Powder Coating Works
There are two types of powder coating: Thermosetting and Thermoplastic. Each type is used for different surfaces, but no matter which type of coating is used, the process is similar. There are multiple steps that need to take place in order to powder coat properly:
Pre-Treatment
To make sure the substrate is ready for treatment, it should first be cleaned to make sure all dirt, grime, grease, and any other substance is removed. If the substrate has material that is stuck to the surface, such as rust or existing paint, this process is often done using a blast room. Blast rooms utilize pressurized liquid or sand-like grit to blast surfaces clean of any debris. Sometimes, a dry-off oven is used as well, which serves two purposes. First, it ensures that the substrate has been completely dried after washing. Second, it can help bring the material up to the ideal temperature for powder coating.
It’s also important to remove any binding materials, especially those that are threaded or sealed. Any nuts, bolts, or lubricated parts need to be extracted before the process begins. Any remaining part of the surface that won’t be coated should be masked.
Application
Once the material has been prepared, it’s ready to be coated. Like painting, Powder Coating uses a gun to spray the coating onto the substrate. Unlike painting, however, powder coating relies on electromagnetic charges. Once in the gun, the powder is charged either through electricity or friction. The substrate, on the other hand, is grounded, giving it the opposite charge of the powder in the gun. Because opposites attract, when the powder is sprayed out of the gun, it will automatically be attracted to the substrate, coating it completely. As long as the substrate is grounded, multiple layers of coating can be applied.
Many non-metal materials can’t be grounded, and so the application process is different for them. Instead of being coated using electrically charged particles in a gun, they are preheated and then dipped into the liquidized powder.
Curing
Following the powder application, it’s necessary for thermoset materials to go through a curing process to turn the powder into a film. When it’s heated, the powder melts and then flows together which creates the strength and durability that powder coating is known for. It also doesn’t melt again after this first time, meaning substrates that have been powder coated can be used for many different purposes, even if heat is involved.
The heating process usually involves heating the substrate to temperatures that range from 325-450°F, for anywhere between ten minutes to more than an hour. However, the substrate’s size and shape may influence the temperature and time needed for curing outside of those parameters. The heating process is accomplished using a convection oven, an infrared oven, or a combination oven that combines both types.
Material Considerations
Powder coating is a great way to both protect a substrate and exponentially increase its durability. However, it’s important to keep in mind that for powder coating to be the right option, the substrate needs to be able to withstand the high temperatures it will be exposed to during the powder coating process. There are also different types of powder coating materials that offer different benefits to different materials.
Thermoplastics
Materials that are thermoplastics are classified as synthetic materials that are able to be formed multiple times. These materials can melt in high temperatures, meaning they are ideal for reforming and recycling but not for situations where the material is exposed to intense heat when reformation isn’t required. However, some thermoplastics are ideal for powder coats due to their wear-resistant and chemical-resistant qualities. Nylon, polyolefin, polyvinyl chloride, and polyester powder are thermoplastics used for it’s durable and sleek finishes.
Thermosets
Thermoset powder coating materials go through a chemical cross-linking process that is permanent when cured. When thermosets cure, they become harder and more brittle than thermoplastics. Epoxy, epoxy-polyester hybrid, acrylic powders, and silicon-based powders are thermosets used for the powder coating process. These materials have different benefits and drawbacks depending on the use of the powder-coated material.
Powder Coating Solutions
General Kinematics provides equipment designed to make the powder coating process more effective and durable. The GK VIBRA-DRUM® Grinding Mill is proven to efficiently grind powder coatings in preparation for coating materials. General Kinematics also provides various durable equipment, like conveyors, feeders, and more!
General Kinematics has been a leading manufacturer of high-quality equipment for more than 60 years. With our talented team of engineers, GK is able to provide customized equipment and parts designed specifically for your industry needs. Contact us today to get started.
