Powder Coat Wood?

Painting

We’ve been working on a project (MADE3) that is pushing us into finishing wood. So far, the process is painful and tedious. After brushing on a VOC-free primer, that took forever, we upgraded to a High Velocity Low Pressure airless sprayer. It covered the surfaces well, but due to operator inexperience, too thickly. Dry time is a factor plus it tied up shop space. Drop cloths protected most of the area, but spraying does put put paint in the air where it is free to be breathed in and to settle and dry in tiny little speckles on everything since we do not have a proper spray booth.

On the upside we are learning… like with everything we touch that there must/should be a better way.

Our goal is a perfect wood finish, fast, safe, no waste, and no harmful chemicals. This sounds like an impossible list of criteria until you look around and realize this is the same goal as most industrial processes. So what are they doing?

First, they use painting robots! It gets a great finish, is fast, and safe for us but still uses aerosolized paint and not really an option for us. Not many hobbyist robotic sprayer projects out there yet.

Powder Coating

Moving away from liquid paint takes us to powder coating. This process was originally developed for coating metal. Much like with the platings available, the ability to pass an electric charge through metal can be used to coat it. During chroming or anodizing, the part is submerged in liquid with a charge so another material can bond to the part. Powder coating is a dry process. By electrostatically charging the part, the powder is passed through a gun of the opposite charge. The smoke-like stream of powder is attracted to and sticks to the part. The powdered part is then placed in an oven where the powder melts and self-levels across the part. Depending on the polymers used in the powder, different colors, textures, hardnesses, and other properties of the coating can be achieved.

Can you powder coat wood?

Wood doesn’t play well with moisture so the dryness of powder is good. Most powder coatings available are rated non-toxic and many are considered sustainable and “green”. Powder is released into the air but can be controlled with static charge for safety and collecting for re-use. The trick to powder coating wood appears to be getting the powder to stick to the wood and then keeping it there.

Wood does not conduct electricity nearly as well as metal or at a safe voltage. Wood does not handle going through an 800 degree oven.

How do they do it?

The techniques we’ve found in use are:

1. Conductive Primer - the wood part is first painted with a conductive primer that will take a charge so the powder sticks2. Low Temperature Powder - polymers that react correctly at lower temperatures3. UV Curing - the wavelength of ultraviolet light causes the polymer reaction instead of heat and completes in minutes

How can we start doing it?

We’re still researching, making some calls, and sending emails. UV is very interesting.