We got started powder coating metal parts a few years ago and were surprised to learn it isn’t hard, it isn’t expensive, and it can be preferred to painting for a few reasons. Here, we’ll describe the process and demonstrate on the after-market cast-iron differential housing covers for my ’06 Jeep TJ. 🙂
We have a Eastwood Powder Coating System that can produce a rugged coating for electrically conductive parts (and more, which I’ll mention later). Powder coating is actually the application and bonding of a fine polymer that melts to the surface as well as to itself. The coating is stronger and more resistant to scratches and wear than regular paint. The initial process creates an electric charge between the metal part and the application gun. Powder is sprayed at the metal and the electric charge causes it to stick. The dry process makes it easier to clean up and doesn’t smell from solvents when used indoors. Our setup works best for parts that fit inside the kitchen oven in the workshop.
Caution: once you’ve powder coated in the oven, it shouldn’t be used for cooking food. Get a second-hand oven for this purpose.
Powder coating is fast because it can be applied and cured in less than an hour and not require the cure time that paint does. However, it is more difficult to work with multiple colors or blend colors though that is possible by taking the hot metal out of the oven and applying the second color to the hot first layer. This is useful for creating that beautiful candy appearance for some colors. It’s also a method of applying powder coat to materials that aren’t conductive, such as glass, as long as it can tolerate the 450F cure temperature.
- Remove any rust or oil residue with acetone. This includes finger prints, so use clean nitrile gloves once the materials have been cleaned.
- Mask off any features that are not meant to be coated. Since the curing process requires high heat to cure, we must mask with kapton tape, silicone plugs, and aluminum foil rather than standard tapes and paper.
- Since the powder is applied dry, it can be easily removed with a wet paper-towel if necessary. This might be useful for applying another color to raised lettering.
- Purchase a color from various suppliers including Eastwood. Matte finishes tend to hide surface imperfections much better than glossy finishes and thus requires less prep.
- Clean out the application gun with compressed air gun to make sure there isn’t any contamination.
- Install the color bottle into the gun before installing the compressed air line. The regulator on the application gun should be set to 15psi.
- Plug in the Eastwood base and set to “I” for a thinner coat and “II” for a thicker coat. The electrical voltage self-regulates the thickness of the powder since the thick powder prevents retaining additional powder. Therefore, you can’t really overcoat it, only waste powder by overdoing it.
- Attach the alligator clip on the metal part. Some creativity may be required if there isn’t a good spot to connect the alligator clip that doesn’t also need coating.
By applying coats in station nearby, we can limit overshoot and the amount of cleanup required.
- Remove any grates and turn on the oven to 450F or the recommended temperature for the specific powder.
- Slide the oven grate into your coating station. TIG Welding Rod provides a strong material for hanging parts from the underside of the grate if you have it handy or it can be be placed on top of the grate.
- Coat the materials with the powder. Rotate the grate or individual parts to ensure even coverage. Use the extra blue tip on the gun to get inside some recesses. The tip forces powder out laterally to get to different surfaces.
- Gently carry the materials to the oven so the powder doesn’t shake off and place inside. Let cure at temperature for 20-30 minutes. Since it’s set to the melt temperature, you won’t burn it by leaving it in too long. Remove and let cool.
For more information, Eastwood produced a great video about their system that might help fill in some blanks.