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Post by PowderMarket on Apr 3, 2014 23:37:07 GMT
Hey everyone!
This forum is for all of you powder coaters out there! Does anybody have any questions for me? I'd be happy to answer them for you
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Post by innovativecoatings on Apr 10, 2014 15:50:07 GMT
What is the best way to clean an existing coat of cured powder prior to applying a second coat? Say for example, a piece that was powder coated a few years back and a customer wants a fresh coat applied.
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Post by PowderMarket on Apr 10, 2014 16:12:39 GMT
Hey there!
To answer your question, phosphating is not an option! The chemicals will actually burn "water spots" into the finish and offer no positives.
Solvents are also out. They will damage the existing finishing.
Best case scenario is probably going to be a really good degreaser such as Simple Green. You are wanting to remove any oils and dirt from the surface. My preference would also be to, at a minimum, scotch-brite or lightly sand the part prior to the 2nd coat. Intercoat adhesion may be an issue.
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Post by innovativecoatings on Apr 10, 2014 16:25:14 GMT
Would de-natured alcohol be a good candidate?
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Post by PowderMarket on Apr 10, 2014 16:30:11 GMT
I have used it before. I would cut it about 30% with water though. The alcohol alone can be a little strong and may start to burn into the powder (depending on the powder).
Also, make sure to use a lint free rag.
Great Suggestion!!
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Post by innovativecoatings on Apr 10, 2014 19:47:24 GMT
Thank You.
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Post by prmarkets on May 1, 2014 19:10:19 GMT
We are having a major problem getting black speckles whenever we coat. I have a parker ionics gun with a box vibrating machine and as you taught us in class i have new hoses for every color. I take the gun apart as far as i can and i even take the wand apart as far as i can, and i blow them both out for a good 10 to 20 minutes, but yet i still have black speckles whenever i do color. They are hard to see, yet they are still there. is this normal, or should i shoot myself?
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Post by PowderMarket on May 1, 2014 19:14:41 GMT
prmarkets,
I'd ask you how it's been going, but I think you've already answered that question . Let's see if we can talk you down off the cliff and solve the problem.
Black specs in your powder? I'm assuming it's showing up in all colors since you mention that you are changing hose. Although it could be particles flying around in your oven, those most often appear as "trash" and not "specks".
I'm going to assume as well that the part is clean. Unclean parts are going to have more problems than simply specks.
Even though I haven't been to your shop, I'm gonna take a stab in the dark here. I want you to take a very close look at your compressed air supply. Do you have an air dryer located very close to the gun? Is it working properly? Are you 100% sure? If very small particulates of oil are getting through your air line, they will cause very small, dark colored specks throughout your powder. I've seen people chase that problem for months only to find out it's the air. Clean your gun VERY well, put on a new hose, and attach to a small portable compressor and see if the problem disappears. Just remember to REALLY - REALLY - REALLY clean ALL your gun parts if you do determine this to be your problem.
Let me know if my crystal ball worked or if we need to go back to the drawing board!
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