Epoxy Etching Products?

Discussion in 'Boatbuilding' started by jahmes143, Mar 31, 2019.

  1. jahmes143
    Joined: Dec 2018
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    Location: Florida

    jahmes143 Junior Member

    I just put new glass over the majority of my hull interior (bulkheads, stringers, etc). Now I'm prepping that glass for paint. I can scuff sand a lot of the large surfaces, but there are many areas that are impossible to completely sand dull. For example, lots of little corners, and also I would be sanding through the weave to get down into the weave valleys, thus compromising the glass.

    I could sandblast to the tune of big $$$.

    Are there any roll/brush on products that would sufficiently etch/abrade the glossy finish of the epoxy to promote paint adhesion?

    I am painting with Rustoleum Enamel with Valspar hardener additive.
     
  2. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    jahmes143

    Having decades of professional experience in industrial painting and fiberglass; My advice is to relax and don't worry so much about the preparation for painting. Don't bother with sandblasting.

    Rustoliem has tremendous adhesive properties. It will bridge the minute gloss points left in the weave. They will not cause adhesion failure.

    Cosmetically:
    Any weave pits will definitely telegraph thru and appear in final finish. Only you can determine the cosmetic quality you will accept.

    I don't wish to dwell on mistakes you might have made. If you are sanding into the fibers, then there was not enough resin applied. If you desire a completely smooth finish, then now is the time to use fairing compound.

    Good luck
    I'm curious as to how it comes out. Keep us apprised with lots of pictures.
     
    philSweet likes this.
  3. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    If you have weave pits and want a smooth surface, fill them with epoxy or epoxy/ filler.
    Sanding thru the peaks causes an immediate loss of strength - you might as well not have applied new cloth if you sand much.

    I see I said the same thing as Blueknarr.
     
  4. Ilan Voyager
    Joined: May 2004
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    Location: Cancun Mexico

    Ilan Voyager Senior Member

    I do agree with Blueknarr. I'll just add; wash the surfaces with water and soap. Rince well and dry. That cleans the carbamate residues on the resin.
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Cutting into a biax thread with sandpaper does little to affect the strength of glass.

    If you mean cutting below two stands of woven; that is a big no-no. But typically; you would either neat coat the woven or fair and neat coat, etc.

    If you neat coat 2-3 layers wet on green and sand at the end; you'll be well above the woven.
     
  6. jahmes143
    Joined: Dec 2018
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    Location: Florida

    jahmes143 Junior Member

    Thanks for the advice, folks. Cosmetics are of no concern, as most of these areas are below deck and out of sight. Just trying to coat the epoxy to prevent UV degradation and make it look halfway decent if ever someone pops their head down there.

    Currently testing paint adhesion on areas of varying texture. Impressive results after 72 hours. Even on a high gloss epoxy substrate the rustoleum adheres very well and takes a really hard fingernail to scrape it off.
     
  7. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Fingernail scrape off at 72 hours is low for Rustoliem. What is your temperature and ventilation? How thick of a coat? Did you scrub away the surface amines? As epoxy cures, amines rise to the surface, they will interfere with adhesion.
    Thick coats in low temperatures and poor ventilation will take longer to cure.

    IMO bilges should be smooth. I want to be able to clean them with paper towels. Dirt, grease and grime will collect in pits, causing problems for future painting.
     

  8. fallguy
    Joined: Dec 2016
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    Location: usa

    fallguy Senior Member

    You generally sand for adhesion.

    What is the glass weight?
     
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