The modern powder coating process

Application and Equipment

Powder is usually applied with a spray gun. Most guns are similar in their function of spraying the powder. Each gun has a control unit that regulates the voltage being generated and rate at which the powder is delivered from the hopper

Spray Booths and Recovery

Powder booths are very similar, but use two distinct types of recovery equipment, cartridge filters or a cyclone separator. Each style is particularly suitable for a different type of application. To select the appropriate system, you should consider the production size, finish quality of the desired coating, the number of different types or colors of powder being used, and the frequency with which they are changed.

What Type of Powder is Used?

Powder is a dry coating. Instead of being dissolved or suspended in a liquid medium, such as solvent or water, powder is applied in a granular form. Powder coating is created by blending the various components (binders, resins, pigments, fillers and additives) and processing them through an extruder into a continuous mass. This homogenous mass is cooled and broken into small chips, which are then ground into the powder. Each powder particle contains within it the necessary components for reforming into the finished coating. After the powder is applied to the part, typically using an electrostatic spray process, the part passes through an oven and cures, melting into a smooth film on the surface of the part.

How is the Powder Applied?

The application process involves applying a charge to the dry powder particles and spraying them onto a grounded substrate. The substrate, or part, is typically grounded through the conveyor or hanger holding the part. The powder, once attracted to the part, is then held on the surface until it is melted and cured into a smooth coating film in the bake oven. The spray process takes place inside a booth designed to contain the oversprayed powder and makes it possible to collect and reclaim it for re-use. The reclaimed powder is mixed with a proportionate amount of fresh virgin powder for reuse, achieving consistent results and up to 98% material utilization.

Why Powdercoat?

Over the past decade, powder coating has been increasingly accepted as the preferred finishing process. The reasons for this conversion from wet to dry powder can be attributed to three major forces:

Economy

1) Material utilization is much higher with powder, making your material costs much lower. 92%-98% of the powder you buy will be applied to the parts you are finishing versus an average of 60% with an electrostatic liquid system (The other 40% is waste and must be disposed of). 2) Since most of the material is used on the part, there is very little waste to be disposed of. Powder is not considered hazardous waste, so the cost of disposal is minimal. 3) Air used to exhaust the powder spray booth is returned directly to the plant, eliminating heating and cooling costs for the make-up air required when air is vented outside the plant.

Excellence

1) The cured powder finish is less susceptible to damage than a liquid finish. There is less need for repair work on the finished item. This results in the need for much less elaborate packaging saving time and cost on re-working and packaging. 2) Epoxy, acrylic, and hybrid powders provide excellent adhesion and harness for improved resistance to chipping, abrasion, corrosion, and chemicals; Ant it is flexible enough to be formable without cracking 3) Polyester powders provide additional advantages in ultraviolet and weathering resistance.

Ecology

1) Stringent regulations are being aggressively enforced in an effort to control air pollution and hazardous waste disposal. 2) Powder coating eliminate solvent fumes and VOC's from spray booths and oven exhausts that pollute the air. 3) Potentially toxic sludge and water that can contaminate the earth and must be disposed of as hazardous waste is eliminated.

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