You may not realize it, but Eastwood was the first to bring DIY powder coating to the masses and into your garage. We've been there since the start and I'll admit that we sometimes forget that not everyone is as educated as we are about the process. I decided to throw together a list of information that will give you a crash course on powder coating as well as some tips and tricks along the way.
Powder Coating is a pneumatically sprayed on coating that is applied in powder form and is attracted to the part electrostatically (think static cling). The part being coated is grounded and the powder is negatively electrostatically charged as its sprayed out of the gun. The charged powder clings to the grounded part and won’t fall off even when sprayed upside down or in tight areas. Powder Coating is different from traditional paint and coatings because it does not require a solvent or activator to cure. Heating the part and powder until it fluidizes and flows out cures powder. Powder can be applied thicker and in a more uniform manner because of the way it cures leaving a thicker, tougher finish. Another difference from traditional coatings is that once powder “flows out” (goes from a powder to a liquid) and then cures it can be handled immediately (albeit hot).
Surface Prep is much like traditional paint in which the part itself NEEDS to be as clean as possible and free of any contaminates. They also should be abraded to give the coating something to “bite” or “grab on to for optimal adhesion. Media Blasting before powder coating is the preferred and best method if the part can be blasted. Additionally powder coating will react and bubble, peel, or delaminate if it's applied to a dirty or contaminated part.
The powder coating process is fairly simple once your part is prepped for powder. The first step is to fill the powder gun cup with your desired color powder (making sure the cup is as clean as possible) about ½ to ¾ full. You then hang or lay your part out in a manner in which you can coat as much of it at one time as possible and hook the ground cable to the part or metal touching the part. With the gun and part prepared you can Attach a compressed air hose to the gun and manually adjust the air pressure down to around 10-15PSI.The last step before spraying is to plug the power source into the electrical outlet and choose your desired voltage output (if your gun has this option). A higher voltage will cover a large area better while a lower voltage will help you get into tight or hidden areas.
Now you can spray the powder by pressing the trigger on the gun. Some guns like our dual-voltage hotcoat gun requires you to push a separate trigger button to activate the power source. As you're spraying the powder be sure to keep the tip of the gun approximately 8-12" from the part. DO NOT get too close to the part or the gun tip will arc on the part and could potentially ignite a fire!
With the part covered in powder you can now insert the part into a pre-heated oven (temps vary by powder) and bake for the appropriate time until the powder "flows out" or turns from a powder to a liquid form. Once the powder has flowed out your powder may require you to change the temperature in the oven to bake and cure the powder. Be sure to leave the part in the oven and do not handle it once it has just flowed out as the powder may still be "wet" and could smudge!
While the above process is a cliff notes version of the process, I think it should give you a basic idea of what it takes to powder coat items at home. Below are a handful of important powder coating terms that you may come across once you're further introduced to the hobby.
1. Faraday Cage Effect- A condition in which powder does not stick to an area or is difficult to apply powder to. Commonly it is on shapes with compound curves, cracks, crevices, or indentions. On higher end machines like the Eastwood Pro Gun or Dual Voltage gun and other higher end guns have adjustable voltage outputs to correct this.
2. Fluidize- When powder and compressed air are mixed to suspend the powder.
3. Out Gassing- Air or Gas that escapes from beneath the powder surface during curing. This can be from improperly prepped parts or from not allowing cleaning chemicals to fully evaporate before applying the powder. This term is also used to describe the process of pre-heating a part to release the gasses before applying the powder by some.
4. Reclaiming- The process of collecting overspray or left over powder that didn't stick to the part. This excess powder can be sifted and reused to coat additional items. Some of the lower priced powders on the market are reclaimed from industrial powder coating production lines. Eastwood powders are VIRGIN powders and NOT reclaimed.
5. Hot Flocking- The process of pre-heating a part to the curing temperature of the powder and immediately applying the powder to the part. This aids in adhesion and film thickness build. It also is necessary for powder coating items that have low or no conductivity like acrylic, glass, etc. and occasionally when applying multiple coats including custom colors and clear coats. Be careful as this process is easy to overcoat a part and cause running as it cures on the surface as you apply the powder.
6. Flow Out- When a powder is heated and goes from a dry, coarse powder to a liquid state.
7. Gloss Level- Measured in Percentage- This is how shiny or glossy a cured powder or paint is.
Let's face it, no one is perfect, but we can all work to get better! Below are some common errors I've commonly made as well as we've heard of from customers.
1. Improper Cleaning- Often times beginners will skip media blasting a part and just wire brush or spray brake clean on a part and then try and powder coat it. The result is fisheyes, pimpling, lifting, and other imperfections because of outgassing. We ALWAYS suggest to media blast, clean with PRE, then pre-bake the part before applying powder. Cast aluminum parts and larger parts may need to be pre-heated to outgas the impurities numerous times, especially items that have housed or been subjected to oils their entire life (oil pans, valve covers, transmission cases, rears, etc)
2. Under Curing- Each powder has a specific flow out and curing temperatures and times. In order to achieve the full durability of powder coating you MUST follow these temps and times. Under Curing a part can be seen when the part is still soft or wet to the touch after removing it from the oven and easily scratching or flaking off of the dried powder.
3. Over Curing- Some powders, especially lighter colored, chrome-effects, and translucent colors can discolor, bubble, and yellow if too much heat is applied to them when curing.
4. Heavy texture, Dripping, lumps, or hard mounds on the surface- This is from too much powder being applied in one spot. Most commonly this happens when someone is hot-flocking a part.
5. Powder wipes off once cured- This is an instance where the part has grease on the surface under the powder and the powder is only as good as the surface it is laid over.
Over the years we've picked up a lot of little tips and tricks and we seem to get a lot of the same questions about the capabilities of powder coating as well as the process, so below I compiled some of our favorites.
1. Can cured powder be wet sanded and buffed?- Sort of, it does not act like a traditional paint because the surface is so tough. It can be a little difficult to wet sand and buff it like a basecoat-clearcoat paint. Using 2000 grit paper and a swirl remover or finishing compound can remove light orange peel and imperfections, but be very careful on candies, translucents, etc as it can change the final hue of the color and make things worse.
2. Is powder coating stronger than paint? Yes, because of the way powder is heat cured and bonded to an item it tends to be more durable, but remember it isn’t a miracle coating!
3. How long does powder coating last? As long as the part itself if you have correctly prepped, applied, and cured the powder.
4. Can powder be applied over rust? Yes it can, but it has NO rust fighting properties and will not completely stop the rust, but it can slow it down if applied properly.
5. How does powder compare to paint for coverage? An 8 ounce container of powder is comparable to 2-3 aerosol cans of paint.
6. How do I get powder to stick to crevices, cracks, and indentations in a part? Run the powder coating gun at a lower voltage to help powder get into tight areas (dual voltage gun has 15k and 25k volt settings)
7. When applying multiple coats of powder allow the first coat to flow out, then remove it and apply your next coat so that the top coat will flow out and the two will cure and interlink for the ultimate durability.
8. Test removing and installing your parts into the oven before applying the powder to make sure it will fit and it isn’t too difficult to get it into the oven.
9. Use a damp finger or foam brush to wipe powder off of raised surfaces before curing powder to reveal polished or bare metal for that detailed professional look.
While this isn't everything involved in becoming a powder coating master, this should help jumpstart you into coating your own parts. If you'd like to learn more about the process and the science behind powder coating be sure to get yourself a copy of the Eastwood Powder Coating Handbook written by our resident powder coating expert Joe Richardson.