Dry Powder Coating

Product Knowledge

What is dry powder coating, and how does it work?
Dry powder coating is a coating method used to apply a dry, fine powder onto a substrate surface. It is a solvent-free and environmentally friendly alternative to traditional liquid coatings. Dry powder coating involves the application of electrostatically charged powder particles onto the substrate, followed by a curing process that melts and fuses the powder to form a durable and protective coating. Let's explore how dry powder coating works in more detail:

1. Powder Composition:
Dry powder coatings are typically composed of a mixture of resin, pigments, fillers, and additives. The resin serves as the binder that holds the powder particles together upon melting and curing. Pigments provide color and appearance, while fillers enhance properties such as hardness or texture. Additives may be included to improve flow, levelling, or UV resistance.

2. Powder Application:
The dry powder coating is applied to the substrate using an electrostatic spray gun or fluidized bed system. The powder particles are negatively charged as they pass through the spray gun or are fluidized in the bed. The substrate, typically grounded, carries a positive charge. The electrostatic attraction causes the powder particles to adhere to the substrate's surface, creating a uniform coating.

3. Powder Deposition:
Once the powder particles contact the grounded substrate, they adhere to the surface due to electrostatic attraction. The charged particles are attracted to areas with an opposite charge, leading to a controlled and precise deposition. The electrostatic nature of the process ensures efficient material utilization, as excess powder can be recovered and reused.

4. Powder Coating Thickness:
The thickness of the dry powder coating is determined by factors such as the powder formulation, application technique, and substrate geometry. The thickness can be controlled by adjusting the powder flow rate, spray gun parameters, or the number of coating passes. Typical coating thicknesses range from 20 to 120 microns, depending on the application requirements.

5. Powder Coating Curing:
After the powder has been applied to the substrate, it undergoes a curing process to transform the dry powder into a solid, durable coating. Curing is achieved through heat, typically by passing the coated substrate through a curing oven. The oven temperature is set to a specific range that allows the powder particles to melt and flow together, forming a continuous and cross-linked film. The curing temperature and duration depend on the specific powder formulation and desired coating properties.

6. Fusion and Cross-Linking:
During the curing process, the powder particles melt and fuse together, creating a cohesive and cross-linked network. The cross-linking of the resin molecules ensures adhesion, hardness, and chemical resistance of the coating. As the coating cools, it solidifies, forming a tough and protective layer.

7. Curing Methods:
There are various curing methods used in dry powder coating, depending on the powder formulation and substrate requirements:

   a. Convection Oven: The coated substrate is exposed to a controlled convection heat source, typically in a batch or continuous oven. The oven provides uniform heating, allowing the powder to melt and cure evenly.

   b. Infrared (IR) Curing: Infrared radiation is used to heat and cure the powder coating. IR curing offers rapid heating and shorter curing times, making it suitable for heat-sensitive substrates or applications with high production speeds.

   c. Ultraviolet (UV) Curing: UV-curable powder coatings are formulated to cure rapidly when exposed to UV radiation. UV curing offers instant curing, energy efficiency, and low-temperature processing, making it ideal for heat-sensitive substrates and fast-curing applications.

8. Post-Curing and Cooling:
Once the powder coating has been cured, the substrate is allowed to cool to room temperature. This stage is crucial for the coating to achieve its final hardness, adhesion, and other desired properties.