Combining Durability With Long-Term Versatility.
Powder coating first emerged in the late 1940s, with commercial products available by 1952, and has since become common in many everyday items. Early powder coatings used thermoplastic resins, which remain in wide use today. Thermoplastic coatings are medium-density plastics applied to metal parts for decorative, protective, or combined purposes. Applied as a powder and melted with heat, they create a uniform, durable layer that can be reheated and re-melted for repairs — a key difference from thermoset coatings, which cannot be re-melted once cured.
Applying thermoplastic coatings
The most common method for applying thermoplastic coatings is a process called fluidized bed dipping. In this method, metal parts are preheated to between 360°C and 400°C, depending on the specific application, and then dipped into a bed of thermoplastic powder. Compressed air agitates the powder, giving it fluid-like properties (hence the term ‘fluidized bed’), which allows the powder to melt and wrap evenly around the heated metal, forming a relatively thick coating of 200 microns or more that covers the entire surface.
This was the first powder coating method developed and remains highly effective today. However, newer techniques like electrostatic spray application are also widely used. In this process, the powder is electrically charged so it adheres to the metal surface before the part is heated in an oven, melting the thermoplastic into a smooth, uniform layer. What sets thermoplastic coatings apart is that they undergo no chemical change during heating and curing. As a result, if the coating is damaged or imperfect, it can be reheated to melt and flow again, repairing the surface — something that isn’t possible with thermoset coatings, which permanently cure and cannot be re-melted.
Types of thermoplastic coatings
A variety of materials are used as thermoplastic coatings, including low-density polyethylene, PVC, nylon, polypropylene, and thermoplastic polyester, each chosen for its specific performance qualities. Polyethylene was the first material used for powder coatings, known for its excellent corrosion resistance and outstanding electrical insulation. Warm to the touch and easy to clean, it’s often applied to items that people handle frequently, as well as laboratory equipment that must resist corrosive substances.
PVC coatings typically require a primer to achieve good adhesion but maintain flexibility, making them ideal for parts that undergo fabrication after coating, such as bending or drawing. Nylon, which also bonds best with a primer, is extremely durable and has a very low coefficient of friction, making it suitable for bearings and other moving components.
In its natural state, polypropylene is nearly inert and must be chemically modified to adhere effectively to metal surfaces. Once treated, it provides robust weather and corrosion resistance similar to polyethylene. Lastly, thermoplastic polyester bonds well without a primer and is highly weather-resistant and colorfast, making it an excellent choice for outdoor metal furniture and similar applications exposed to the elements.
The advantages of thermoplastic coatings
Because thermoplastic coatings can be applied much thicker than other powder coating types, they provide a durable, single-layer solution even for the toughest environments. Warm to the touch and softer than hard-shell coatings, they’re comfortable to handle, which is why they’re commonly used on handrails, handles, and other high-contact surfaces.
The thick plastic layer also delivers excellent electrical insulation and minimizes heat transfer, making it ideal for items like refrigerator shelves, where both waterproofing and thermal properties are important. As the molten material flows smoothly around the object, it creates a continuous, seamless surface that covers edges and corners well, resulting in a long-lasting finish with strong UV resistance to maintain color over time.
While appearance options are somewhat more limited than with thermoset powder coatings, thermoplastic coatings are free from VOCs, halogens, and BPA, making them an environmentally responsible choice, a factor that is increasingly valued today. They also offer cost advantages, thanks to both the relatively low material cost and the efficient application process, making thermoplastic coatings an economical solution for a wide range of uses
Where are thermoplastic coatings used?
Powder coatings are everywhere — you probably come into contact with them daily without even realizing it. Among these, thermoplastic coatings stand out for their unique properties, making them ideal for a wide range of uses. Around the home, they’re commonly found on dishwasher baskets and refrigerator shelves.
They’re also widely used on metal fences, from chain link to solid steel or aluminum panels, as well as on handrails that feel soft and warm to the touch. In heavy industries like oil and gas, thermoplastic-coated pipes are common thanks to their durability and corrosion resistance.
Their excellent electrical insulation makes them invaluable for electrical applications such as battery boxes, cable trays, and automotive parts. Their strong resistance to salt and moisture also suits them well for marine environments, while stadium seating often relies on thermoplastic coatings to provide durable, comfortable, and weather-resistant surfaces.
In short, thermoplastic coatings offer long-lasting, attractive protection in countless applications, wherever a tough, versatile finish is needed.
