Cage Information

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.

Color is added to powder coatings during the manufacturing process, ie before the powder reaches the powder coater.
There is little that can be done to change the color consistently, once the powder leaves the manufacturing plant.

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 produces a high specification coating which is relatively hard, abrasion resistant (depending on the
specification) and tough. Thin powder coatings can be bent but this is not recommended for exterior applications.

The choice of colours and finishes is almost limitless.

Powder coatings can be applied over a wide range of thickness.

Colour matching is quite acceptable batch to batch.

Maintenance

Maintaining the initial appearance of a powder coating is a simple matter. The soot and grime which builds up on
surfaces from time to time contains moisture and salts which will adversely affect the powder coating and must be
removed. Powder coatings should be washed down regularly. The coating should be washed down with soapy water
-- use a neutral detergent -- and rinsed off with clean water.

When they are maintained regularly, they should be relatively permanent. The correctly applied coating, although not
metallurgically bonded to the metal will not crack, chip or peel as with conventional paint films.