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Thread: Epoxy blistering

  1. #1
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    Default Epoxy blistering

    I crawled under the sharpy look for any rough spots before painting applying the bottom paint. the outside of the boat is xynol cloth layed with epoxy and another coat of epoxy Then it was painted with porch and deck latex paint. That was at least two years ago.

    I got a nasty surprise. There are blisters, not many and the largest is about the area of my hand. I can peal these blisters off with a dull chisel. The blisters are soft and sticky, and the epoxy surface underneath is sticky but hard.

    What can I do to make this area cured and hard? Epoxy hardliner, acetone, heat?

  2. #2
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    Default Re: Epoxy blistering

    Bummer.

    Read this thread over on the CLC Builder's Forum.

    What brand of epoxy?
    You careful about hardener:epoxy ratio when mixing?
    Thorough mixing?

    Just the last coat of epoxy over the xynol?

    Or is the cloth blistering too, from underneath?

    Hull's inside also epoxy-sealed even without any cloth?

    After this long a time I'd venture your best recourse is to scrape as much of the bad epoxy off, including the xynol if that's lifting, then scrub with soap & water, rinse thoroughly, let dry, then sand, then remove every trace of sanding residue & dust. Then apply fresh epoxy, mixed according to manufacturer's instructions, along with patches of xynol where you'd removed the original sheathing layer. Allow thorough cure as instructed.
    Last edited by sp_clark; 08-14-2021 at 02:32 PM.

  3. #3
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    Default Re: Epoxy blistering

    reads to me that an acetone party is on your horizon once you get the blisters removed

    sw
    "we are the people, our parents warned us about" (jb)

    steve

  4. #4
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    Default Re: Epoxy blistering

    You need not use toxic acetone. White vinegar will do the same thing.

  5. #5
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    Default Re: Epoxy blistering

    Quote Originally Posted by willin woodworks View Post
    You need not use toxic acetone. White vinegar will do the same thing.
    True enough, also much less costly for the quantity needed and not flammable.

  6. #6
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    Default Re: Epoxy blistering

    What is blistering? The epoxy from the wood? The flaketex paint?Who did the job?

  7. #7
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    Default Re: Epoxy blistering

    I did the job. The xynol cloth was laid with epoxy, System Three general purpose resin and activator, two to one ratio per instructions. Then another layer of epoxy was applied. That was at least two years ago. It was painted with latex porch and deck paint, also a long time ago. The paint and the last layer of epoxy raised and formed blisters. The xynol and epoxy below that seem smooth and tight under the blister. There are just a few blister and the side of the sharpie are smooth, and were done at the same time.

  8. #8
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    Default Re: Epoxy blistering

    OK so I'm going to go with the 'insufficient preparation' theory as to why you've seen blistering/delamination of that last coat of epoxy. Took the paint with it, the paint likely as not had nothing to do with the bond failure.

    What may also have contributed might have been some degree of epoxy film failure leading to water ingress between the last coat and the xynol+epoxy matrix underneath. This also could have been from contamination of some sort, leading to a failure in the epoxy film even if imperceptible to the naked eye.

    I'd simply remove any paint-bearing epoxy that's suspect, feather-sand the boundaries around these areas as well as proper sanding of the exposed surfaces underneath, then wash with water. Let dry, patch as needed, paint when epoxy's fully cured after washing that last repair coat.

  9. #9
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    Default Re: Epoxy blistering

    Sounds like blush between the 2 coats of epoxy.

  10. #10
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    Default Re: Epoxy blistering

    Quote Originally Posted by wizbang 13 View Post
    Sounds like blush between the 2 coats of epoxy.
    Agreed.

    System Three has a thorough discussion of the chemistry behind epoxy on their website.

    Near the end there's a paragraph dealing with amine blush and why it can form. Some formulations are less prone to it than others. It's easily removed if you suspect it's there and I guarantee you it will be a real PITA if overlooked or ignored.

  11. #11
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    Default Re: Epoxy blistering

    Quote Originally Posted by wizbang 13 View Post
    Sounds like blush between the 2 coats of epoxy.
    X2, but I wasn't there.

  12. #12
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    Default Re: Epoxy blistering

    blushing...

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