POWDER COATING TECHNOLOGY

                                                                           POWDER COATING TECHNOLOGY

Powder coating is by far the youngest of the surface finishing techniques in common use today. It was first used in Australia about 1967.

Powder coating is the technique of applying dry paint to a part. The final cured coating is the same as a 2-pack wet paint. In normal wet painting such as house paints, the solids are in suspension in a liquid carrier, which must evaporate before the solid paint coating is produced.

In powder coating, the powdered paint may be applied by either of two techniques.

* The item is lowered into a fluidised bed of the powder, which may or may not be electrostatically charged, or

* The powdered paint is electrostatically charged and sprayed onto the part.

The part is then placed in an oven and the powder particles melt and coalesce to form a continuous film.

There are two main types of powder available to the surface finisher:

* Thermoplastic powders that will remelt when heated, and

* Thermosetting powders that will not remelt upon reheating. During the curing process (in the oven) a chemical cross-linking reaction is triggered at the curing temperature and it is this chemical reaction which gives the powder coating many of its desirable properties.

The process of power coating

The powder is applied with an electrostatic spray gun to a part that is at earth (or ground) potential.

Before the powder is sent to the gun it is fluidised:

* to separate the individual grains of powder and so improve the electrostatic charge that can be applied to the powder and

* so that the powder flows more easily to the gun.

Because the powder particles are electrostatically charged, the powder wraps around to the back of the part as it passes by towards the air offtake system. By collecting the powder, which passes by the job, and filtering it, the efficiency of the process can be increased to 95% material usage.

The powder will remain attached to the part as long as some of the electrostatic charge remains on the powder. To obtain the final solid, tough, abrasion resistant coating the powder coated items are placed in an oven and heated to temperatures that range from 160 to 210 degrees C (depending on the powder).

Under the influence of heat a thermosetting powder goes through 4 stages to full cure.

MELT, FLOW, GEL, CURE

The final coating is continuous and will vary from high gloss to flat matt depending on the design of the powder by the supplier.

Powder Coating Application

Powder Coating has become the fastest growing finishing technology. More and more finishing engineers have switched from liquid finishing to powder coating as the way to produce high quality, durable finishes. Powder Coating maximizes production, improves efficiency and complies with increasingly stringent environmental regulations. It is a dry finishing process, using ground particles of pigment and resin which are electro statically charged and sprayed onto a part to be coated.