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Thread: Clear coat cracking problem

  1. #1

    Default Clear coat cracking problem

    Hello,

    I have a sporatic problem with clears applied over other colors of cured powder. Sometime, but not always, I get hairline "spider web" cracks in the clear. Its usually where there is a curve or angle in the part. It doesn't seem to appear right away, but over the next few days after application. Does anyone know what might be causing this? Under cure? Over cure? To much heat? Not enough?

    Thank you......

  2. #2

    Default Clear coat problem

    Hey, I'm having a problem with the clear also. I can apply it over polished aluminum with no problem but get orange peel whenever I apply over cured powder. Are you having this problem as well?

  3. #3

    Default

    Quote Originally Posted by jcolesdad
    Hey, I'm having a problem with the clear also. I can apply it over polished aluminum with no problem but get orange peel whenever I apply over cured powder. Are you having this problem as well?
    No, I do not seem to have a problem with that. Flow out has been good and I get very little if any orange peel. I did have problems with coverage that looked kind of like orange peel, but in reality I was not getting enough clear on in various areas. I curred this by making sure that I was getting good metal to ground clamp contact and by preheating the part for five or ten minutes prior to putting the clear on. I apply the clear while the part and base color are still hot, etc. I make sure I have no bare spots by checking all over with a flashlight before putting it in the oven, etc.

  4. #4

    Default Cracks in Clear Powder

    The cracking is a classic indication of undercure. This could be caused by under time or under temp. I experienced this same problem when we were first getting involved with powder coating. I had coated a piece of chrome and a few days later I noticed the spider web crack pattern. I placed the part back in the oven for another cure cycle and the cracks went away never to return.

    In the interim, Iíve coated numerous parts without a recurrence of the cracking problem. The problem will very likely go away if you increase the cure time.

    You can test to make sure your getting a full cure with an impact test or solvent wipe test. A properly cured Polyester or Polyurethane finish should not leave much color or soften significantly when lightly wiped with a rag with MEK. If you lightly strike the surface with a screwdriver blade there should be no chipping.

  5. #5

    Default

    Thank You GB!!!!! That is exactly the information I was looking for. An under cure is what I suspected, but was not sure. THis really puts my mind at ease. I now know how to prevent it in the future. Thanks again......

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