There are two common processes in powder coating – fluidized bed and electrostatic spray. Though there are many other options when it comes to application - airless hot spray, electrophoretic deposition, plasma gun and flame spraying - these two are the only ones widely used. The very first method used in powder coating is the fluidized bed. Up until now, when using thermoplastic powders, this method is still preferred over any other. Thermoset powders also use this method if the resulting coat requires a high film build such as those utilized as electrical insulation. Fluidized bed works by pre-heating the parts using a temperature which is higher compared to the powder’s melting point before it is put in a fluidized bed. The plastic powder then melts and fused into the part.
Electrostatic spray process is commonly used when thermoset powders are applied. Electrical charge is applied on every particle of the powder before it is sprayed on a grounded surface. Accumulated charged particles then turns the surface into a charged one. With this process, the thickness of the film applied is uniform.
Powder coating uses two types of powder – thermosetting and thermoplastic. Thermoplastic are often used when chemical resistant coating are required because of its property. It is also flexible and tough. For these types of powders, the material often used is nylon powder coating. Thermosetting powder, on the other hand, is more stable compared to thermoplastic and does not melt even upon heating. There are three types of material used when making thermosetting powder – acrylic, epoxy and polyester. These types are usually used on spraying applications since the particles are very fine and it provides a thin film coating on the material’s surface.
- Epoxy. These types of powder coatings possess various qualities. These are chemical resistant coatings, abrasion resistant, tough, adheres properly, flexible and resistant to corrosion. If the kind of film needed is tough and durable then this is the best option as long as the product does not stay in the sun for long. Once it is subjected to sunlight for a long time, its appearance become chalky.
- Urethane. Its qualities are great retention of glossiness, resistance to humidity for over a period of time and the corrosion resistant. Used when thin film is required.
- Polyester. This is used if long term durability is required on the exterior and exhibits great mechanical properties as well as resistance to high temperature.