Powdercoating: An Overview
Ever wonder what's involved in creating a powdercoat finish?
Bob Hogsett (metalguy) gives us a great overview on applying this durable finish.
This is for all of you out there who have heard the term, but have never really understood the process. Powder coating is a finishing option for many components on motorcycles, cars, or basically any metal part, that is used in applications where durability is a must. Manufacturers of wheels, suspension components, and the industrial sector have been using powder coating to protect metal for years. It is mainly used on parts that are subject to harsh environments, or cannot be easily cleaned often, but where protection from the elements is a must. Because of its typically industrial nature, it is not as "deep" or as high quality finish as paint, so it is rarely used where beauty is the prime reason for a coating. Having done it for quite a few years as a hobbyist, I am writing this to give some information to my friends so that they will know what it is, and just how the whole process works.
|Photos courtesy of Eastwood Company|
Surfaces to be powder coated that must meet three crucial criteria:
- They must conduct electricity (read metal)
- They must be clean, and free of other coatings (no rust, or paint, grease…)
- They must be able to withstand the 400 degree cure temp for 15 minutes. This last requirement pretty much leaves out soldered parts like radiators. (Believe me, I tried it!)
That being said, this technology is a fairly simple one, and I will explain how it works! It's WAY simple!
But first, let's go over the equipment you'll need. I bought my hotcoat brand gun at Eastwood tools. (www.Eastwood.com). I have worn one of these units out, but then I have used it a LOT, even coating an entire 400 C.U. Cadillac engine block for a friend's hearse…heads, too! With proper care, it would last a "normal" person a lifetime! This unit can be had for under $100.00. They also sell a "pro" model, for around $700.00, but I am a cheapskate. Harbor Freight tools sells one, which I have tried, but do not recommend it. I just didn't like the results. I also tried their powder, and it seems you get what you pay for. The best powder I have used, however, came from a local powder coating company, that buys it in bulk. Eastwood's powder is also great, and adequate for most uses.
The powder in question is BASICALLY a powdered plastic. It is applied to the part with a low-pressure "fog", and is attracted to the part via an electrical charge imparted to the powder once it has been fluidized by the gun, and fogged onto the part. The part itself has an opposite charge to it, supplied by a ground clamp, so the particles are attracted to all areas of the part being coated. Make sense?
Now that the part has a dull coating of plastic dust, it has to be melted onto the part. The part can now be placed into an oven, or an infrared lamp can be used for this purpose for parts too large for an oven. I use an infrared lamp presently, as many parts are odd-shaped and I have no dedicated oven at present. This brings up an important point, and that is a DEDICATED oven must be used. This means you cannot be using your food oven for this! Otherwise your roast chicken will taste like powder coat.
To continue, once the part has cured, the powder coating will take on a smooth, somewhat orange peel finish to it. Some finishes do not have any orange peel, others just seem prone to it. Satin finishes, flats, all use the same process, the finish just turns out different, one from the next. Transluscents can be applied over chrome pieces, and are very smooth, allowing the chrome to show through the transparent coating, taking on its color. There are so many finishes available, it is hard to include all of them, but some available are: wrinkle finish, translucents, metallics, high heat, and gold vein.
Once the part has cooled after curing, it can be used, simple as that. It is done!
This process is fairly fool-proof, with few exceptions. I must stress that the part is to be clean!! ANY oil will cause fisheye, like with conventional paints, as the powder will not adhere to oil. This means castings like fork lowers can be a challenge, as castings are fairly porous, and once they have held oil, it stays in deep crevasses and comes out with heat….see the problem? Another kind of metal that is hard to coat over is anything zinc-coated, or galvanized. It gasses at a fairly low temperature, and makes fissures in the powder finish. (Been there, too!)
If you mess up powder coat, it can be fairly easily removed with conventional paint stripper. I have tried other means, and stripper seems the best way, as sandblasting is a long, hard way to remove this tough finish. In conclusion, I hope this is informative, and will help anyone who is thinking of having parts done, or just buying the equipment, and doing them yourself.