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by Mike Holler
Powder coating is more durable than typical spray bomb paints. It gets shot on in powder form, then is baked to a tough, nearly indestructible finish. The colors are limitless, and the cost is very affordable. What? Yes, I did say affordable!
If you send small parts out to have powder coated, the cost isn’t all that much. In fact, to coat the two pieces on the intake side of a turbo would cost less than $50. A better option for those that are restoring a car (like Allpar’s own Bob O'Neill) would be to invest in an entry level powder coating outfit. Eastwood sells their starter kit for about $100 (depending on whether it’s on sale or not) that gets you the gun and a ½ pound of reflective chrome powder. Most of Eastwood’s powders come in ½, 2, 5, and 10 pound containers. Basic colors are about $9 per half pound. They even have specialty and high temperature powders. The deluxe kit gets you 3 powders, silicone plugs, a spool of stainless steel wire, and a roll of high temperature tape.
Besides the powder coating kit, you’ll need a source of compressed air. Fortunately, the powder coater only needs 8-10 psi at extremely low volume. The cheapest air compressor you can buy will suffice. In fact, a used 20# propane canister and a cigarette lighter air compressor will do it.
You will also need a way to strip the parts to bare metal. I have a large air compressor and 2 different sand blasters. For previously powder coated pieces or for epoxy enamels, I like to use a chemical stripper before sand blasting. It’s much easier that way. A chemical stripper may be sufficient to remove all of the previous coatings. It won’t do much for rusted parts, though.
Last, you need an oven. Do not use your kitchen oven for powder coating. The fumes will linger in the oven and when you cook your next dinner, your food will be tainted. This stuff will make you rather sick and the food won’t taste too good either. I got a used oven for free just by watching the local papers. In fact, I have a spare stove in the shed that someone is welcome to come and get for free.
Besides the typical single color coatings like black, red, yellow, ad naseum, there are candy colors that require a chrome base coat. The turbo scrolls pictured above are such colors. You can also do multi-colors like these valve covers.
I’ll run through a couple of parts with you so you can get the hang of it. I’m always doing valve covers and such, so follow along as we do some drop-dead gorgeous coating.
First step is to remove the old coating, grime, rust, scale, etc. A chemical stripper will loosen up and remove tough coatings like powder coating and epoxies. I then sand blast to remove the last of the coatings and give the part a rough surface that the new coatings can easily adhere to.
After blasting, the part will need cleaned. Aluminum parts can be thoroughly washed with water to remove all of the sand residue. Steel parts will rust almost instantly if washed with water. I blow steel parts off with compressed air to remove as much of the sand as I can. Then I rinse them with Brakleen to get the last of the fine dust off. Again, I blow them off with compressed air.
After the parts are clean, they get laid out on a rack or other clean surface. There is a ground clip that needs to be attached to the parts as they are sprayed. Clip this in a nondescrete area. There will be a little spot that gets covered by the clip that won’t have coating on it.
Next adjust your compressed air source to about 8-10 psi. Screw a color cup onto your gun filled about 1/3 full of the color you are going to spray. Hold the button down to energize the powder coater, then spray. Coat the tight and low-lying areas first. As you do, much of the powder will float to other areas. Most colors do not require a thick coating, just enough to add color. If coating in the winter it is advisable to pre-heat the part to assist adhesion. Even in the summer you will find that the coatings stick better if you heat the part to about 200 degrees F.
After the part is coated, place it in the oven for 5-20 minutes at 425 degrees. Thin sheet metal will be fully cured in about 5 minutes, while an engine block may take as long as 45 minutes to cure. A short cut that works pretty well is when it starts smoking, it is usually cured. After it is done baking, remove it from the oven and allow it to cool.
Small parts should be hung on the rack with wire. Larger parts can be laid on the rack. Be aware that wherever the part touches the rack, it will mar the coating. If it is a part that has a good side and an unseen side, it won’t matter. Parts that will be seen the whole way around should be hung. Professional powder coaters hang practically everything, even truck frames! Their ovens are large enough to drive cars into, though.
Candy colors require a chrome base coat. There are a couple of variations of chrome, but most work well with candy colors. Step one is to shoot the part with the chrome, then bake. After it cools somewhat (even 200 degrees is cool enough) shoot the top coat. The end result is dazzling. The more coats you apply, the harder it is to get the powder to stick while spraying. Heating the part will help it to stick better.
Another cool trick is multi-colors. Aluminum valve covers are good candidates for multi-colors. Fins and words can be made one color, and the body can be made another color. This isn’t as hard as it might seem at first. We simply prep the part as usual, but shoot the accent color on first. Put another way, shoot the color that will stick up above the surface of the body of the part first. With the Chrysler Turbo valve covers, we shoot the color for the fins and the “Chrysler Turbo” first.
After it cures and cools, shoot the body color. With a damp lint-free cloth, carefully wipe the tips of the fins and the words off. When doing this, the part must be cool enough that the next coat won’t melt, otherwise you can’t wipe off the accents. Removing the freshly shot body color from the fins will expose the previously shot accent color. After you’re satisfied, bake again. What you have then is something to be proud of.
Total investment for a functioning powder coating outfit can be under about $500, with the air compressor eating up the bulk of the cost. Sand blasters can be bought new for around $50 and ovens are cheap or free.
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