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Thread: Epoxy question

  1. #1
    Join Date
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    Default Epoxy question

    We about to copper coat in a few weeks , I ask copper coat UK advise on the keel Which is steel and they suggest if I didn't know if it's been epoxy to strip it back to bare metal and give it two coats of epoxy ,
    My concern is exposing the bare metal to the air and end up given me more problems at a later date with rust .
    One question is I would had thought the keels would had some kind of epoxy from new ? in which case would it be obvious when I reached that far sanding ?
    Question two .
    What the advance/ disadvantage of using a solvent or non solvent epoxy ? I understand a non solvent has to be overcoated once it's gone tacky ( 24 hours ) and a solvent can be over coated at a later date .
    Boat is a 2001 Moody 42 .
    Last edited by sailaboutvic; 20-09-19 at 07:19.
    Warning forumite dyslexia near by
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  2. #2
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    Oct 2012
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    Default Re: Epoxy question

    When I coppercoated my keel I had it shot blasted & I primed it with an epoxy primer supplied by the coppercoat people. They do not supply it anymore so one has to source a primer one's self.
    Most industrial specs for blasting & painting steel, state that steel should be painted within 20 minutes of blasting. I did do this, but made the mistake of not putting enough epoxy on the keel. As a result I have had to re coppercoat the keel this year. I had to grind out a considerable number of areas & re prime then coat the entire keel.
    I used a Sika epoxy product for the primer as I had it from my contact in the roofing industry, where it is used for coating steel prior to overcoating with liquid plastics. Plus it is thick so it built up the level with the areas of the existing coppercoat to give me a smooth surface. The problem with patching is that one has to fair in the edges & this can expose more steel which has to be primed again & then if not enough primer goes on, one is back to square one.

    However, the point of this post is to forewarn you to paint the surface immediately you expose the steel & make sure you put several coats of epoxy on. If not, you may find, like me, that you are doing it again in 4 years time. 2 coats is not enough- in my opinion.
    Last edited by Daydream believer; 20-09-19 at 07:56.
    It is all down to the fact that my wife does not understand me !!

  3. #3
    Join Date
    Jan 2017
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    21

    Default Re: Epoxy question

    I've completed a full strip back on hull and keel on my 1998 Dufour.

    I had both slurry blasted. In the case of the keel, the 'blasters' left the keel to go rusty for 48hours then dry-blasted the rust/salts etc off leaving clean & dry keel.
    We may have applied overkill on process but we coated with an adhesive promoter, a coat of high-build filler and then five coats of epoxy before applying anti-foul.

    My original hope in blasting was that we could stop at the 'epoxy' layer, supposedly five coats applied from new. Although epoxy layers are thin....we assessed it might have had two coats but certainly not any more so we couldnt save it.
    Five coats is the recommendation and if you're copper-coating i might suggest it would be unwise to skimp.
    Give me a shout if you want to know any more detail about our process.
    Cheers
    John

  4. #4
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    Me: Johannesburg South Africa Yacht: Richards Bay East Coast Africa
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    Default Re: Epoxy question

    I have a teel boat, I grit blasted the whole boat than painted it with epoxy primer whithin an hour. Thi was in a very low humidity area. The quicker then better.

    I then painted below the waterline with 4 / 5 coats of epoxy tar overcoating within 24/48 hours.

    If the time gose longer than 48 hours you need to sand to create a mechanical key for overcoating.
    Life is too short not to have a sea view
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  5. #5
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    Default Re: Epoxy question

    Thanks for all the reply so far .
    We in Sicily and it's impossible to get it blasted here , so the yard is going to sand it .
    As I said , two folds
    A I not sure what the advantage or disadvantages of solvent epoxy?
    B if the keel as already got some kind of epoxy covering , it be great to leave that on so not to go down to the steel .
    What do I need to look for .
    We scraped and copper coat our last boat but it was almost new at the time , I sword if I had to copper coat again I let someone else do the dirty work .
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  6. #6
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    Winter in Falmouth, summer on board Rampage.
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    Default Re: Epoxy question

    I’d operate on the principle that the keel hasn’t been epoxied. Even if it has getting back to just the epoxy having removed the antifoul will be next to impossible. Get the yard to take it back to bare metal and then follow it with an epoxy primer. IIRC AMC recommend International Interprotect (https://seamarknunn.com/acatalog/Int...AF5_60882.html) as a coating to go under the CC. When I was talking to them, they recommended as many coats as I could afford from a money and time perspective but at least 2 and preferably 5 coats. Didn’t actually do the keel, too many other things for in the way.....

  7. #7
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    Feb 2013
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    Default Re: Epoxy question

    Sounds like you have two choices..
    A) Take a chance and not take it back to bare metal with the possibility the coppercoat might fail on the keel or B) Strip it back, apply interprotect or similar and then coppercoat which MAY still fail..

    We just did our boat earlier this year, we have a lead keel so had to take it back to bare metal and VERY quickly apply interprotect with coppercoat on top of that.. Guess we will find out at the next lift if it has stuck..

  8. #8
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    Default Re: Epoxy question

    Is it rusting in large areas? If so, whatever coating it may have has already failed and needs redoing anyways, even if it was epoxy. Easy decision then.

    If it's not rusting in large areas (I expect it will be in some spots at least), you will still need to strip off the old antifoul, and with sanding it will be very difficult to do this without harming any epoxy undercoating, which isn't that thick. It may be doable with careful sanding though, and immediately patching up any damage done or small rust spots.

    Definitely can't leave iron exposed for very long at all, I've seen rust spots grow on a freshly blasted hull for the time it took me to drink a cup of tea. This was on a steel trawler done by (very very expensive) "professionals" and even so it took too long between blasting and primer and the next year there were rust bubbles all over the hull and the owner very disappointed. Unfortunately Sicily this time of year will be rather humid :-/

    Interprotect is probably the right product and does cure hard. I don't think Coppercoat is compatible with polyester gelcoat or similar resins that stay tacky unless mixed with wax (flowcoat) or covered up and so there is no reason to consider products like that.

    Good luck Which yard are you in?

  9. #9
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    Default Re: Epoxy question

    Quote Originally Posted by Yngmar View Post
    Is it rusting in large areas? If so, whatever coating it may have has already failed and needs redoing anyways, even if it was epoxy. Easy decision then.

    If it's not rusting in large areas (I expect it will be in some spots at least), you will still need to strip off the old antifoul, and with sanding it will be very difficult to do this without harming any epoxy undercoating, which isn't that thick. It may be doable with careful sanding though, and immediately patching up any damage done or small rust spots.

    Definitely can't leave iron exposed for very long at all, I've seen rust spots grow on a freshly blasted hull for the time it took me to drink a cup of tea. This was on a steel trawler done by (very very expensive) "professionals" and even so it took too long between blasting and primer and the next year there were rust bubbles all over the hull and the owner very disappointed. Unfortunately Sicily this time of year will be rather humid :-/

    Interprotect is probably the right product and does cure hard. I don't think Coppercoat is compatible with polyester gelcoat or similar resins that stay tacky unless mixed with wax (flowcoat) or covered up and so there is no reason to consider products like that.

    Good luck Which yard are you in?
    We just been lift out to day , we in the small yard near where the police and customs boats are moored in Siracusa,
    where there are what looks like steel piling for a breakwater of some kind .
    Look like we be here for some weeks , considering the cc need 5 days then everything as to be moved to do the bits where the stands are , could be here for a month or so if all goes to plain ,
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  10. #10
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    Default Re: Epoxy question

    pressure washing have sorted the problem with the keel , its taken a lot of the paint off to the bare metal so it's going to have to be epoxy
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    www.bluewatersailorcroatia.webs.com

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