6/17/2013
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Q: If I’m heating angle iron that has been powder-coated, and the angle iron has to reach a temperature of 400°F before I start the 1 hour and 15 minute timing process, how do I know when the angle iron reaches the 400°F? B.W., Bullard, Tex.
A: You’ll need a temperature recorder, preferably a chart recorder with air/metal probes, to get the data you need. You may buy one of these units, and if you’re seriously in the coating business, you should have one high on your must-have list. If money is tight, maybe you can borrow one from your powder supplier and then run several samples of the angle, all of the same gauge, and record the data. Then you’ll have a pretty good idea at what point, time-wise, the metal should reach the beginning of the cure rate. The risk here is the unknown factor, such as oven temperature variances that cause really cold parts versus parts that may be warmer than the test pieces. You can ease your mind by running a cure test to be certain you have what you need. I don’t know how large the angle is you’re coating, but 1 hour and 15 minutes is a very long cure cycle. The powder might have a cure time of 15 minutes at 375°F, for example. It shouldn’t take an hour to get to the beginning of the cure curve unless the oven isn’t working properly. I would look for another powder, unless there are extenuating circumstances that you haven’t mentioned. –G.T.
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6/10/2013
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Q: I have black powder from one of my suppliers that has an odor problem. What test should I conduct to check the components in that powder for bad odors? M.W., Brampton, Ont.
A: The resins (mostly) and other chemicals that make up the powder formula create odors when the material is being cured. This odor will change for different resins or additives. However, I’ve never heard of any of these materials being pungent or really causing a problem. Some liquid paints have pleasant odors, actually (for a paint guy, anyway). Some have peanut oils; some have banana oils. I used to be able to tell who the paint supplier was to a plant by the odors coming from the ovens. I’m not aware of a test that will tell you what additives are causing an objectionable odor. If you can get a breakdown of the coating chemistry, and if you can buy a small sample of each, then you could bake out the samples to see which one is causing the problem. Then what will you do? If your supplier has developed and approved a powder with materials that you don’t like because of odor issues, the supplier may have difficulties finding or developing a substitute. And then the supplier would have to go through the whole approval process again. Maybe masks are in order. Maybe you could create some air currents to move away the stagnant air. –G.T.
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6/3/2013
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Q: Is there a method to reduce powder buildup on booth ceilings and walls, and allow the collectors to capture the powder? I’m having issues with powder buildup on the ceiling and powder falling on parts of different colors (white falling on black). Would isolating the ceiling from ground be dangerous? I’m thinking that this would reduce buildup. K.T., Spring Lake, Mich.
A: The powder world has tried for years to fix the problem that you mention, with only moderate success. Of course, some people will say they succeeded, but don’t believe everything you hear. Sounds to me as if you’re trying to do a color change without proper cleaning of the booth. Nothing will beat a squeegee, an air gun, or both, although we don’t like to use air guns in a booth because they’ll cause powder to escape the booth and mess up the surrounding area. Isolating the booth ceiling would be creating a capacitor out of the ceiling. And even if the ceiling is plastic, some powder will stick to it. Try the "mechanical" cleaning method, which would be a squeegee. If you’re not getting the booth clean by this method, maybe you should check out how it’s being done. If line time is an issue, maybe an additional body for cleanup is needed. I’ve seen powder booths cleaned well, ready for a new color, in 12 minutes by two guys who paid attention to each other and what they were doing. Maybe a little training is needed. –G.T.
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5/27/2013
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Q: We have a company that powder coats our 0.060 inch thick carbon steel parts with a hybrid textured powder finish. The powder manufacturer recommends a powder thickness of 2.0 mils to 3.0 mils on our carbon steel parts. To avoid rejecting any shipments that have a higher film thickness, we’re accepting any part that has 1.0 mil to 5.0 mils. Recently, we’ve been receiving parts with up to 15.0 mils and as low as 0.6 mil. When assembling the parts, we don’t have a fit problem with some of these parts, that is, we could accept them; however, I need to know the reasons for not being able to control the film thickness as specified by the powder coater. Also, are there any problems associated with having high-film-thickness powder coating on a part? Note: Our units are installed indoors. We also have a pooling issue on the inside edges and corners. I.K., Calgary, Alberta, CD.
A: I bet you do have a pooling problem. I can think of no reason for the film variance. It shouldn’t be, and you should stop it. You’re fortunate that you’re not having fit problems. Interior use, unless there is a corrosive atmosphere, means someone is wasting a lot of material and creating the pooling as well as orange peel appearance problems. Powder this thick when it’s designed for much lower coverage will usually get brittle at some point and might prematurely fail. You should stop accepting material that’s out-of-spec. Your powder coater is enjoying himself, unless he’s buying the powder, in which case he needs to be replaced by a more conscientious coater. Getting the film build under control should take care of the pooling problems. –G.T.
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5/20/2013
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Q: How can I remove the electrocoat (e-coat) surface layer without damaging the underlying metal surface? Please help. N.D., Rochester Hills, Mich.
A: What is the substrate metal? You can burn off e-coat the same way you can burn off powder. You can chemically remove the e-coat by using a chemical paint removing method. Sanding isn’t practical because you can’t get into every nook and cranny. I think the best method is with a chemical immersion system. The magazine includes a list of companies that can sell you these systems, or you can find stripping companies that will do it for you. See the magazine’s online buyer’s guide on this Web site. The chemical method won’t cause any distortion to the substrate. A key is the makeup of the substrate, which you didn’t mention. –G.T.
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5/13/2013
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Q: I have a couple of issues. First, when coating a custom yellow, I get a gritty look to the finish. Second, the finish has a dull look to it regardless of cure time. J.S., Griffin, Ga.
A: I have worked with the custom yellow powder you’re using and haven’t had either of the problems you mention. What that tells me is that you may have a bad box of powder or dirt is getting on the part surface somehow between cleaning and coating. The dull finish? Those two problems seem to be material-related. You need to try a fresh batch of material. Try spraying a sample on a test panel to see if the results are the same. If they are, it will likely confirm my first thought -- bad powder. –G.T.
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5/6/2013
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Q: I have several pieces of copper-plated motorcycle parts. I wiped down the parts with MEK (methyl ethyl ketone), applied a clear coat, and cured them slowly, but the results were a yellowing that looked almost brassy, or golden, not copper at all. I prebaked the fender beforehand to rid it of any hidden buffing compound residue. When the prebake was over, the fender was a bright shiny copper, but the clear coat rid it of all that shine. Any suggestions on what might have happened? J.H., Minneapolis, Minn.
A: What about the cure temperature? Maybe it was a bit too high. Clear coats have a tendency to go to the yellow side of the chart with no assistance from anyone, and a slight elevation in bake temperatures will do it for sure. The MEK should get rid of any buffing compound, especially if you wipe and then rinse and wipe. I don’t believe the prebake is necessary. Actually, it might aggravate the problem. And slow baking might just get the part a bit too hot and contribute to the yellowing problem. Clears are a bit tricky to deal with, and any deviation from a straight-line process could set you up for a part that’s not truly a clear. –G.T.
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4/29/2013
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Q: I have a project that requires anodizing to AMS 2488 type II over thin titanium and painting with Pyromark Series 1200 flat black paint. The part has many areas that are very difficult to paint by conventional means. My question is, can powder coating be done over anodizing? Does powder coating come in a flat finish, and can it withstand temperatures up to 1200°F? E.N., Silver Creek, N.Y.
A: You were doing fine until the last part. Yes, you can powder coat over anodizing, but it has some subtle problems. The problems don’t arise in every case, so talk with your powder supplier and be sure the supplier knows what it is you want to do with the material. You can get powder in a flat-gloss finish. In fact, you can get it in any gloss you desire, from flat to high gloss.
Now the problem: There are powder coatings applied to exhaust manifolds that can withstand 1200°F, but they may present a problem with the anodizing. I’ve never done it, and I don’t personally know anyone who has, so there may or may not be an issue. The temperature requirement may affect the other properties you’re seeking. The magazine’s December Reference & Buyer’s Resource Issue includes powder suppliers who can meet the heat requirements. Go to the home page and click on Online Buyer’s Guide. Certainly one or all of these companies will help you with your specifications. –G.T.
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4/22/2013
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Q: We’re having tremendous powder separation issues. Too much resin is getting on the part before the oven, and it’s causing a brownish, dull gray look to the finished product. We’re trying to get a textured silver. Any info you can provide will be gratefully appreciated. C.J., Webster, S.Dak.
A: Sorry, I fail to understand how too much resin is getting onto your parts. By my definition, the resin base of the powder is only part of the total powder recipe. By my definition, therefore, I’ve never heard of the resin separating from the other powder chemicals and causing a problem. If you mean you’re getting too much powder on the part, then that’s another matter. I suppose too much of the powder formulation you’re using might cause the coloring issue you see, but I don’t know that for sure. If you’re getting too much total powder, the answer is to reduce the film build on your parts. I get the feeling that this isn’t the issue here because the answer is too simple. Maybe a better description of what’s happening would be helpful. –G.T.
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4/15/2013
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Q: I just got into the business. I have been doing parts with just a single coat but recently had a request for multiple coats. I said sure, thinking it would not be a problem for I had read some on applying multiple coats while still hot and other various tips. I used a gloss black with a 350°F oven temperature and 15 minute cure time. So, I sprayed and cured for 10 minutes then resprayed and cured for the full 15 minutes. Once the parts were done, I noticed a spot that wasn't fully coated, not because of improper prep. It was simply missed. When another coat was applied in the general area of the missed spot and cured for 15 minutes, the result was textured only where the new coat was applied. I don't understand why the result was textured. I assumed it would flow out as if it were the first coat. Any information on multiple coats or an answer to this question would be greatly appreciated. R.C., St. Paul, Minn.
A: Should I assume that the original powder is a standard smooth finish, or is it textured by design? In any event, it's one thing to build film by spraying, partially curing, and then applying a full coat over the first versus attempting to spot touch-up. Some companies apply multiple colors in a similar fashion; however, most times there is a mask line between the colors. Spot touch-up has always been an issue with powder coatings. When a spot on a part requires touch-up, there are two ways to fix the problem. The first is to sand the area, and use a good quality liquid touch-up. This is totally accepted in industry. The second is to sand the rework area, and completely respray the entire part. Spot repair with powder leaves a halo ring around the repair area because powder doesn't flow out like a liquid material. This is what you're experiencing. I would be careful about committing to multiple coats. After the second coat, orange peel gets rather mean looking, and the film can become brittle and break off when struck by an alien device. –G.T.
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