Powder coating is a type of coating that 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”.
There are two main categories of powder coatings: thermosets and thermoplastics. The thermosetting variety incorporates a cross-linker into the formulation. When the powder is baked, it reacts with other chemical groups in the powder to polymerize, improving the performance properties. The thermoplastic variety does not undergo any additional reactions during the baking process, but rather only flows out into the final coating.
Preparing the surface prior to coating is known as abrasive media blasting or mediablasting and shot blasting. Blast media and blasting abrasives are used to provide surface texturing and preparation, etching, finishing and degreasing.
The most common way of applying the powder coating to metal objects is to spray the powder using an electrostatic gun, or corona gun. The gun imparts a positive electric charge on the powder, which is then sprayed towards the grounded object by mechanical or compressed air spraying and then accelerated toward the workpiece by the powerful electrostatic charge.
When thermoset powder is exposed to elevated temperature, it begins to melt, flows out, and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This cure process, called crosslinking, requires a certain temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed. Normally the powders cure at 200°C (390°F) for 10 minutes. The curing schedule could vary according to the manufacturer’s specifications.
At Go Powder we use a 31' long x 12' wide by 10' high Cure Oven. This oven operates via a 3.5MM BTU natural gas burner. All parts are hung and moved via our multi track overhead material handling system capable of up to 15 000 lbs per oven load. Our Powder Booth, is oversized to accomodate the parts plus 2 powder coating techs. We also have a blowdown and prep booth.
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