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Powder Coating

By Jeff Zurschmeide

If thereís one particular enemy of old cars, itís rust. Rust may be slow, but it will destroy your investment in a classic restoration just as surely as driving into a brick wall. So when youíve spent the money to have your car stripped down to the bare metal, you want to protect that metal from rust as soon as possible.

To protect bare metal, you must apply some kind of sealant to help keep moisture away from the surface. Iron and steel will rust, but aluminum will also oxidize, and even stainless steel can be damaged if left untreated.

We divide sealants up into Paints, Powder Coating, and Other Sealants. The latter category includes rust prevention inhibitors, undercoatings, trunk coatings, phosphating, chromating, electroplating, and similar processes. Paints and Other Sealants are covered in separate articles.

One of the most popular sealant treatments used in the automotive restoration (and customization) process is powder coat (also known as powder paint). Simply put, powder coating is a paint-like covering that is applied dry and then baked to a hard-cured finish. Powder coat is both tougher and more flexible than liquid-based paints.

Because of its superior durability, powder coating is most widely used to seal ladder frames, axle housings, and other parts that operate under harsh conditions. Powder coat is especially popular on springs and other flexible parts.

HINT Hint...
If you are restoring for competition, judges will deduct points for using a different product than was originally applied to the car. For many restorers, the answer is to powder coat the undercarriage components and then cover the coating with a layer of authentic paint.

Powder coat is available in hundreds of colors, but the color is not mixed as it is with liquid paint. So you are limited to the colors in the powder coaterís chip book, but most powder coated parts are finished in basic black for restoration purposes.

Powder coating generally costs more than painting, and to achieve the best results you must take your items to a professional powder coating business. Home and small shop kits are available commercially, but because powder coating requires a 350 to 400 degree oven to cure, it is generally infeasible for most individuals to coat larger parts.

Costs to powder coat items vary from shop to shop, and also based on the amount of preparation work required and the kind of coating you request. Most powder coating shops will also blast or dip your parts to clean them, or have a standing arrangement with a parts cleaner. Note that these services add to the price of the work. Generally speaking, an automobile frame can be coated for $200-$300, and the price is money well-spent if you have invested hundreds or thousands more to restore the frame to as-new condition.

Dos and Don'ts
Thumb up  DO
  • Make sure your metal parts are absolutely clean before any sealing
  • Get references and ask for work samples from any sealant shop

Thumb down  DON’T
  • Donít use any filler when powder coating. Powder coating cures at a high temperature, and body fillers wonít tolerate that kind of temperature. Even high-temp fillers donít work, because they have different expansion coefficients than the surrounding metal, and break the powder coat during the curing process
  • Donít try to cover major rust damage with sealant or powder coat. These products offer no structural support
The Popular Restorations Project Car
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1946 Packard: Saving time by powder coating

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Powder coating, more than anything else, saved time and energy while restoring the Popular Restorations project car. At first I planned on powder coating just a few parts, but changed my mind when I found out how inexpensive the process can be. A restoration mechanic suggested I powder coat the carís frame instead of using POR-15, mainly for the sake of appearance. He said it would cost a few hundred dollars but it would be worth it.


Some of the parts before powder coating

Along with the frame I took over 40 additional parts including the coil springs, control arms, backing plates, bumper supports, and the wheels. The Packard frame is very long with an X brace in the middle so it ended up being $400. The five wheels were about $30 each and the remainder was another $150.

That adds up to $700 which sounds like a lot of money, but I donít have a sandblaster or a place to do the blasting. Just getting all of the parts sandblasted would likely cost more than $400, especially considering their 60-plus years of rust and baked-on oil and grease. With regard to the smaller parts, four or five dollars per part is a bargain. Especially when you think of how long it takes to remove the rust, paint, and grease, and then prime and paint each part.

Later on I had a sheet metal shop repair the rusted, front fender wells and then had them powder coated as well. Powder coating isnít exactly period correct for a 1946 Packard but when you come right down to it, neither are modern spray paint formulations. For black parts, the powder coating looks clean and it is extremely durable.

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Interview
 

TufCoat, Inc.

By Jeff Zurschmeide


Rod Watts, President
16200 SW 72nd Ave
Portland, OR 97224
503-684-0508

PR: Tell us about powder coating. What is it?

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.

Recommendations
Click on any item below for more details at Amazon.com

Tracy Norris
Beginning Powder Coaterís Handbook: An Introduction to Powder Coating
Pegasus Aloft Press, Paperback, 2003-12-01
This well-reviewed handbook is a great introduction to the technology of powder coating for the home and small shop. It will guide you, step-by-step, through equipment selection, material preparation, application and curing of a quality powder coat.

NEW Eastwood Hotcoat Powder Coating System Starter Kit

This system allows you to achieve the benefits of powder coating small parts instead of coating them with paint. It requires a compressed air source (5-10 PSI from a portable tank with a regulator or a compressor, and an electric oven or toaster oven. A dedicated electric oven should be used. The kit includes:

  • 8 oz Navy Blue Hotcoat Powder
  • 8 oz Bright Red Hotcoat Powder
  • 8 oz Machine Gray Hotcoat Powder
  • 8 oz Gloss Black Hotcoat Powder
  • Begining Powder Coaterís Handbook
  • Deflector to minimize overspray
  • Fluidizing Attachment
  • (3) Extra bottles for fast color changes
  • (1)High Temp Masking Tape 1/2Ē wide
  • High Temp Silcone Plug Assortment
  • Safety Wire for hanging parts
  • Disposable In Line Air Filter

Hotcoat Powder Coating Cadillac Blue 8 oz
Eastwood carries a number of Hotcoat colors in 8 ounce and 2 pound containers. To see them all, click on this link. At Amazon search for Hotcoat Powder Coating in All Departments, not Automotive.
External Links
Powder Coating magazineís website has a large amount of in-depth information on powder coating. Its target audience is powder coating professionals but itís a great resource for anyone who wants to know more about the subject.
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