Getting Personal With Powdercoat

Once removed from the oven, the finish remains tacky for a few minutes, so we're careful not to touch it or kick up any dust that could settle onto it. As soon as the finish is cool to the touch, the component is ready for service. Clean up and disposal is pretty easy since powders contain no VOC (Volatile Organic Compound) pollutants. The overspray that falls onto the floor is swept up and baked in the oven until solid, then tossed into the trash after it's cured.

HPP: What is the purpose of electro-statically charging the powder?
JT: The electrostatic charge is designed to maximize coverage and adhesion, while preventing runs and minimizing waste. The powder is positively charged as it exits the gun and it's attracted to the component, which is grounded. The charge then dissipates once the piece reaches around 200 degrees in the oven.

HPP: Can you elaborate on the types and colors of powder typically used today?
JT: There are three types we commonly use. Polyester-based powder is the least expensive, while offering excellent durability; it's the choice of most powdercoat shops and home hobbyists. Epoxy-based powder is chemical resistant and offers the highest hardness, yet it's most flexible. Urethane-based powder is typically associated with specialty finishes like a candy coat or a transparent metallic.

Color availability of powder is similar to paint. There's a wide array of flat, semi-flat, and gloss colors available from the manufacturers, and we try to steer customers in that direction. While we can add a limited amount of pearl or metallic to any powder to customize its color for a customer at additional charge, manufacturers can produce virtually any custom color imaginable, but it can be very costly for the customer.

Primer and clear powders are also options, but either can create a build-up of material, which might lessen the definition of a component's small details. Primer can leave a slightly smoother finish, while clear is used to increase depth and overall luster of the finish. Clear is mostly used when attempting to preserve a natural or polished aluminum finish like that of an intake manifold or aluminum wheel.

HPP: Must metal be preheated prior to applying powdercoat?
JT: Only dense, porous metals must be preheated, and that's to prevent "out gassing"-a condition similar to "solvent pop" when using paint. It occurs when the pores of low quality metal open as it warms, releasing gases originally trapped during the casting process. The gases then cause the finish to bubble, which can be difficult to repair.

To combat out gassing, we first preheat the piece to our target temperature and apply the powder immediately after removing it from the oven. The powder actually begins to flow out as soon as it hits the hot metal, and then we place it back into the oven to completely finish the curing process.

HPP: Can rusty components be powdercoated?
JT: Yes, surface rust rarely leaves behind any surface roughness, but a pitted texture is often left after mediablasting a heavily rusted piece, which can be seen in the final finish. High-temperature metal fillers can be used to smooth a metal's surface before powdercoating, but metalwork that includes welding or brazing are options, too.

HPP: How can you prevent coverage on areas not intended to be powdercoated?
JT: We use a special heat-resistant tape to mask off such areas as a wheel's machined lip and place rubber plugs into areas such as bolt holes. If powder does get into an area it wasn't supposed to, we can chase threads with a tap while slots can be sanded or drilled out. Like any job, however, time is money, so if we have to spend a lot of time masking areas or plugging holes, the final cost can reflect that.