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  • non-stick
    replied
    Surface Preperation Re-Visited

    Yet another long winded post by yours truly on surface preperation,folks.

    I know I drone on and on about surface prep, but it really is key in the finishing process. I can't stress to you enough how important it is to do the work here as opposed to be sorry for it later on. After all...as many of you know, removing powder coating is a royal pain in the you know what if your results didn't come out good. In order to avoid that messy process, maybe some of these tidbits will help.

    Ok...so let's just say you have a sharp 90 degree angle on your part and you're ready to powder coat. Hold up right there. Powder coating HATES those edges. As a matter of fact (as some of you have no doubt experienced) it pulls back from a sharp angle only to leave a bare unprotected spot. Let's say it's raised lettering on a valve cover? Now.... it's best to take a die grinder,file or some other means to "round off" the 90 degree edge in this instance. Sort of like creating a transitional phase in the surface much as it would be done with a 3-angle grind on a valve seat. from a 90,then to a 45 degree, back to the 90 therefore creating a machined "round" if you will. Your part will thank you for this in the end. The finished preocess will have a smoothed over effect and therefore better adhesion overall.

    Also.... I strongly suggest investing in Lab-Metal (sold right here on this very website) for filling ANY hole or divot, no matter how minor. This is especially good for cast aluminum which has pock marks. Keep in mind that whatever you coat will retain that profile and only be enhanced due to the gloss of the powder involved. I.E. - It will stick out like a sore thumb! Invest in the Lab-Metal. It's a tough durable product that will withstand the rigors of powdercoating. Quite difficult to sand smooth so be forewarned! If any of you has used Bondo in the past, it's a like minded experience. Funny story actually..... in my younger days of powder coating I was doing a customer's Harley Gas tank. From the factory they come with Bondo on the extreme lobes of the tank to give it that big round "hump" we all are familiar with. Well.... I fancied myself quite the bondo worker as a young'n and I figured that I would do the same with the Lab-Metal (called something else back then). BOY! Was I ever wrong. Stop laughing at me, I was young .I hand sanded and massaged that lump of filler for 3 days straight to get it back to the point where it looked stock. THIS STUFF IS AS TOUGH AS IRON! Go easy with it and please....don't put a big amount on planning to just sand it down later. Take my words for it......you'll be sorry. Baby steps with this stuff,ok? It works, and works well. I highly suggest using it on any metal surface to "ckean it up" before that initial coating. It's also great for scratches or gouges in the metal that will telegraph through to the finished result.
    Another area that I wanted to touch on in this post is plugging threaded holes. I cannot stress to you all enough how important that is. If you coat inside a threaded hole, you WILL be chasing it out with a thread-tap. I promise you that. Get some masking tape from Caswell here and block it off. Some cut a little circle and tape over the hole while others roll a piece into a tube and simply stick it in there. They make silicone plugs and such to be used and if I bug Caswell enough....they will carry those as well. In the mean-time....I suggest just putting a bolt in the thread with perhaps one or two threads screwed in. It blocks the hole and keeps everything clean. Heck...you can even attach a wire to hang your part from in there and have a ready made ground (that's done all the time in industrial powder coating shops around the world).

    Again....there will be more posted about this subject and others in the future. I hope what I've written so far has helped somebody. Take care and have fun with it......Russ

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  • non-stick
    replied
    Coating Technique

    I've had quite a few questions brought to me about "what is or isn't the best technique" in powder coating. There's some general rules to follow here but I've got to say, there's no right or wrong way. Just what works for you. Let's start off with the basics and we'll touch on the advanced stuff in future posts (overcoming Farraday-Cage effect, mottled coatings,and the such). If you have a problem applying....please read on.........

    Basic principals of the powder coating process are thus : You take a polymer (your powder) and disperse it mixed with air, force it through a tube that has a charged direct current field and it therefore becomes charged through osmosis( just being within the charged field). It is then exited the spray gun and attracted to a substrate (whatever metal you are coating) which has a ground attached. There is NO difference between this process and say....rubbing a balloon on your head and then sticking it to the wall. Positives and negatives attract, therefore you have adhesion.
    Onward and upward.....
    I generally start off with my gun a distance of 18-24 inches away from the part. I coat much in the same manner that anybody would with a spray gun or can, the only difference is that I make tiny circles with the tip of the gun while doing this. It helps diffuse the powder that much further and eliminates "spitting" onto the parts. Start in the upper left corner and move to the right. Work "past" the part. Get nice even coverage all over and turn the part around. Same process until the whole thing is evenly coated. At this point I stop and look at what I just did. If any spits or uneven waves in the powder...I can fix it easily using the same process...just blow it off first.
    Now...let's just say for example you have a flat piece of sandblasted cold steel. Maybe 12 inches square. What you are looking for is a "dusted" fluffy type of effect. Think of it this way. You've seen your car windshield with a fresh coating of morning dew on it, right? Well...multiply that by two and that's what you should have looks wise on your part. *Just* barely past noticing raw metal under your coating. Don't worry if you can still see metal in the light. The melt and cure of the flowed powder will cover that up just fine. Any excess and you will notice an orange peeled effect to the powder. lumpy bumpy wavy and pock marks mean excess. Too bright a shine from the substrate and it's not heavy enough. Take your time, work slowly and deliberately and the results will be just fine. If you don't like what you see....blow it off and do it again. That's the major advantage that powder has over all other coatings.
    Voltages for you guys should be in the 20Kv range for a good solid coating. As for second coats like a clear over a colour, we'll attck that on another post. There's no difference between metallics, clears and pigmented powders! They all spray and coat the same. If your metallic has a wave to it or the metallic flake looks a bit odd, you are too close. Back off and re-spray the part. Same goes with clears. Although a finer powder due to lack of pigment.....you should still have that "morning dew" appearance to it. Again, please note...this is for one-coat process only.
    Using this method will usually build a coating of 1 to 1.2 mils which is where you want to be. Until you get a feel for it (and yes, you will) experiment on a bunch of different parts. After all....powder is 100% reclaimable and can be sprayed over and over again, so you have no excuses. Practice makes perfect folks. I hope something in there helped somebody. Take care all......Russ

    Leave a comment:


  • non-stick
    replied
    Surface Preperation

    OK folks....just a brief note on surface preperation.

    A lot of schools of though are split on this one. There are basically two types of adhesion at play. Mechanical and Chemical bonds. Some are gung-ho on the chemical side whereas yours truly likes the Mechanical. (assume we're deciding wether to put a nut and bolt onto something or to superglue it if that helps).
    I've found that in preperation for most types of powder coating, a nice degrease,media blast and solvent wash works best. Of course....the solvent wash could be parlayed by a phosphate wash to get you that home run on your parts. This is what I've found best let's say on mild steel that's fresh from tha machine shop or taken off of one of my cars.

    1) Degrease with a nice solvent. Anything that basically takes the grime and process oils off. Mineral Spirits will do just fine. Wipe off excess solvent with a rag and let dry.
    2) Media blasting. While I do prefer a nice black oxide sandblast to either remove old finishes or paints, it's also a good "surface prep" due to the profile that is acheived. Glass bead to heavy rough oxide falls within this category.
    3) Washdown and smut removal. There are a lot of different directions one could go with here. One way is an ultrasonic clean and a dry off stage in a warm oven. Others may just blow off with compressed air and a quick wipe down with denatured alcohol. Still another process is phosphating the part and then coating. All are acceptable means of degreasing in preparation.
    4) masking and blocking parts to not be coated. Caswell here sells some fine tape that you guys should pick up. Great stuff for high-temperature range where you guys are working. Simply lay it on at this stage and peel off after your part has cooled down from cure. Works much the same as masking for wet-spray applications. You may need to "help" the tape off by scoring a line with an X-Acto knife or sharp blade, but the results are fantsatic. Powder where you only need it!

    There it is in a nutshell, folks. It all equals "what can you do before the oven" as far as how good your finished product will look. Take your time. If only degrease is available to you....do it to the best of your ability and be thorough. If only phospahte (which Caswell also now sells) then do a good job of it. It's all in the preperation. I can't say that enough. Show stopping paint jobs on cars don't just "happen" do they? NO way. They go through HOURS upon HOURS of preperation to have that drop dead sexy look about them. The same holds true for your powder coated parts. Take the time and use as many of these steps as necessary to compliment your work. After all....this is where the men and women get seperated from the girls and boys . Aside from that....have fun with it. Take care all......Russ

    Leave a comment:


  • non-stick
    started a topic Tips and Tricks

    Tips and Tricks

    Hello again all,

    In my infinite wisdome (which is wedged soewhere between "slim" and "none" lol) I thought that maybe a tips and tricks thread should be started. I'll occasionally post helpful tidbits in this column from time to time to help you guys out with questions you may have. I fully encourage each of you to do the same! If you've found something that works for you and may help others please,by all means... feel free to share your success (no matter how unconventional it may seem. If it works, it works. plain and simple). Any question in THIS thread will be ignored, I'm sorry to say. That's what the rest of the board is for. I just thought it'd be nice to come onto at least one thread and get nothing but helpful items that apply to what you guys are looking for as opposed to a whole discussion about every nuance there is in each process. Again.... feel free to post your own success stories and back them up with pictures if at all possible. I'll do my best to do the same.

    Again........tips and tricks and helpful hints only please. If you have a question or there is something said that puts the post in dispute...you always have the ability of contacting it's author via many means and asking specifics about what he/she said. The author always has the right to erase the post if a mistake or error was made as well, mind you. Anything goes....powder comments, oven tips, hanging, coating booth solutions, you name it. If it applies to Powder Coatings, it has a home here assuming you've had luck with it or find it helpful to others. As always......have fun with it,folks. Thanks and regards to all.....Russ
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