RW: Powder coating is an organic finish made from polyester, urethane and epoxy. The chemistry is similar to most liquid paints. To simplify it greatly, powder coating is really a three-part process. First, itís cleaning the metal so that youíre just dealing with the metal substrate. Then thereís the actual powder application, which is done with guns that look like a liquid spray gun, except that they work with the powder media. The third phase is a curing process where the parts go into an oven with a 350 to 400 degree temperature for a prescribed amount of time. Most of the powders are thermal-setting, and they go through a melt and flow and cross-link process that cause the powder to both adhere to the metal substrate and interlock within itself.
PR: Why does the powder stick to the metal?
RW: The powder is charged with a negative charge, and the parts have to be hung on a line or a rack that is grounded, so that you get a transfer of neutrons from the part to the grounding. Thatís what causes the powder to go on smooth and consistent.
PR: What colors are available with powder?
RW: The difference between powder coating and liquid painting is that in liquid painting, you can take a base and mix to come up with any color you want. With powder coating, the powder has to be made by a powder manufacturer. The process requires blending and grinding and extruding and ball-milling. You can blend them, but we generally donít.
PR: How many colors are available?
RW: Iíve got a powder inventory of about 400 to 500 colors. And Iíve got quick and easy access to about 1,000 colors.
PR: Are there any parts that shouldnít be powder coated?
RW: Weíve powder coated almost all parts that go into an automobile. The exceptions would be parts that exceed 200 degrees or so, such as exhaust systems. Most powders will break down under those temperatures over a long period of time.
PR: Is powder more or less flexible than paint?
RW: Powder is more flexible. You can actually take a 3 by 5 metal disc of powder-coated material, and if itís properly cured you can bend it at a very sharp angle and it wonít break. We used to coat automotive springs commercially for one customer.
PR: How does powder coat protect against rust?
RW: Powder has two primary applications, as do liquid paints. Those are metal protection and architectural appearance. Powders tend to be harder than liquid paints, even though they keep their flexibility. Itís a harder surface and itís harder to chip. Powder will surpass almost all liquids. The only things that come close are some of the two-part catalyzed liquids.
PR: Can you paint over powder coating?
RW: Yes, you can. Powder can serve as an excellent primer. The secret is to use a liquid that is chemically compatible with the powder. You need to use a liquid with a hot enough solvent that it will bind with the powder.
PR: Does the metal need to be ferrous for powder coating?
RW: No, we can coat ferrous, stainless, copper, aluminum - the secret is to have a properly treated surface before powder coating. For example, mild steel that has been cleaned and treated with an iron phosphate conversion coating. That enhances the bonding and enhances durability over time.
PR: Can you coat fiberglass and other materials?
RW: We cannot coat fiberglass but we have coated carbon fiber.
PR: How much should people expect to spend to have things powder coated?
RW: A lot of it depends on how much work we have to do to prepare the item. A lot of auto parts come to us prepped and ready to go, because of the level of detail that people doing this kind of work want to accomplish. Not the frames, generally, but a lot of the smaller parts.
PR: If I brought you a Model A frame, prepped and ready to go, what would it cost?
RW: Youíre looking in the range of $250 to $350, in standard black. If someone came in with a newer frame, with a rear end and springs, and assorted other parts, itís more. But I donít think anyone ever leaves here with a bill over $500, unless itís something really exotic.
PR: Does color affect the price?
RW: Colors can make a significant difference in price. Some colors require primer underneath - for instance, some of the pearlescent and silver powders require a white or other color under them to make the appearance what itís supposed to be. When you start dealing with that stuff, you can maybe even double the price. But typically, blacks and whites and grays and blues and even reds are all going to be about the same price. The difference is if someone wants something that we donít stock, they need to buy the powder, too.
PR: Whatís the most important thing to remember about powder coating?
RW: The most important thing anyone needs to know is whether that piece of metal is absolutely clean and ready to coat. Because if itís not, there will be problems.