What is Powder Coating?

Powder coating is a type of dry coating, which is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin." The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as tool chests, aluminium extrusions, and industrial parts. Newer technologies allow other materials, such as MDF, to be powder coated using different methods.

The application of powder is very simple. Filtered, compressed air, usually at 20-30 psi (137-207 kPa) pushes the powder out of the gun past the electrode which gives the powder a positive charge. The part being coated is grounded so the positive powder particles are attracted to it. When the part is completely covered, the ground is removed and the part is put into the oven.

Advantages of powder coating

There are several advantages of powder coating over conventional liquid coatings:

- Powder coatings emit zero or near zero volitile organic compounds (VOC).
- Powder coatings are resistant to chemicals, grease and oils.
- Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging.
- Powder coating overspray can be recycled and thus it is possible to achieve nearly 100% use of the coating.
- Powder coating production lines produce less hazardous waste than conventional liquid coatings.
- Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items.

For optimum material handling and ease of application, most powder coatings have a particle size in the range of 30 to 50 µm and a TG > 40° C. For such powder coatings, film build-ups of greater than 50 µm may be required to obtain an acceptably smooth film. The surface texture which is considered desirable or acceptable depends on the end product. Many manufacturers actually prefer to have a certain degree of orange peel since it helps to hide metal defects that have occurred during manufacture, and the resulting coating is less prone to show fingerprints.