epoxy on a steel boat hull

Discussion in 'Materials' started by mikewade, Jun 9, 2010.

  1. mikewade
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    mikewade Junior Member

    I have been searching the net & back issues of boat design to try & find the answer to a question giving me some food for thought.
    My steel van de stadt is on the hard and I am about to have her blasted clean then epoxy coated.
    My question really relates to film thickness to be applied. The epoxy I am looking at is 3M 152 LV and the manufacturer suggests that this gives a film thickness of 500microns per coat. At this thickness, is 1 coat enough or are 2 or three really the best.Does the panel feel that there is a better epoxy I should use given that 152LV has a touch dry time of 12 hours which here in the North of the UK is not really the best for our inclement weather. I struggle to find a definitive answer. Any guidance you can give me will be gratefully received :?: .
     
  2. kyle@raka.com
    Joined: May 2010
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    kyle@raka.com Junior Member

    Have you ever thought of using coal tar epoxy? I found a great link I can share on here that had alot of helpful information. We just got a bunch of it in to start selling at my company but if what I am reading is correct it was designed and made for bonding to metal.
    The link is http://www.flatsafe.com/LinkClick.aspx?fileticket=8s8bmxMRmJE=&tabid=71
    We haven't had a chance to play with it ourselves yet we were thinking of using it on a boat trailer that is a little rusty.
    If you need more information you can visit my website we should have the coal tar info up by the end of the weak.

    Kyle Dunn
    Raka Inc
    www.raka.com
     
  3. Landlubber
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    Landlubber Senior Member

    ...may I suggest that at least 300 microns is the minimum thickness that needs to be applied for steel seawater protection....read up on the subject, there are many epoxy manufacturers on the web, and they have sonme good detailed info.

    My favourites are the Altex/Devoe range of products, they make protective coatings for the protection of offshore marine structures, and boats come in nicely when you think about it....
     
  4. M&M Ovenden
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    M&M Ovenden Senior Member

    I use Amercoat products (the famous Devoe 235 is exactly same as Amercoat 235). Amercoat has a very good web site with all the info about there paints, great product data sheets. I like companies that give such access to specs of there products. Surf threw there products and case histories:

    http://ppgamercoatus.ppgpmc.com/products/
     
  5. M&M Ovenden
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    M&M Ovenden Senior Member

    The thickness per coat can greatly vary with your application process, brush, roll, air less and depending on your spray equipment and paint thinning. The best to guaranty you get the coverage you want is to measure it. Most paint distributors will give you thickness gage if you ask for one. Saying that I don't think, even if I did measure 500 microns in one coat I would be satisfied with one coat application. I'll leave that to pros painting ships and platforms. You are obviously not a professional painter and will most likely not get a uniform coverage, it would be unfortunate to not get enough paint in some places end end up with some badly covered steel. By applying multiple coats you get better chance to obtain a uniform high build paint coverage.
     
  6. MikeJohns
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    MikeJohns Senior Member


    As you are paying a painter they will reduce your cost with fewer coats. However I think as the others have said you are better putting several coats on. Often a 50 micron quick post blasting coat followed by a high build in one or two coats.

    We have used some high build that can be applied up to 3000 microns in one coat ! Tricky to apply.

    The chemistry of the different types of epoxy curing mechanism are the same regarldless of manufacturer, you pay for quality control and sometimes just marketing.
    Look at the thinners content, some of the high build have no thinners. Some of the expensive brands have close to 20% thinners for an inferior but easier to apply paint.

    I don't think You should use mastic paints like epoxy tar externally for immersion, they are generally unavailable in Australia now since they are a potent health hazard apparently. On the topsides from the sheer down a foot it's a good idea to use a zinc rich epoxy primer but keep it well above the waterline.

    Nearly all polyamide cured epoxies need 10 hours above 10 degrees to properly cure. After this they harden further but the temperature can rise and fall. If the weather is cold use heaters and canvas covers.

    Always watch the dew point as a guide a damp rag when wiped on the hull should evaporate quickly say all gone in a minute. if it beads and remains don't apply epoxy, it'll fall off. Empty any tanks in contact with the hull as that will often casue condensation if its a humid day and the tanks are cold. Then the paint falls off there later on.

    Paint manufacturers and distributors are all in the marketing game, they target their products at certain industries. For example if you go to a Dulux distributor in Australia they'll tell you they have no marine paints! However the chemistry is identical and a very good epoxy is the Dulux polyamide cured epoxy. I've specified it for commercial vessels no problems at all and cheap in large quantities.

    Epoxies don't have a shelf life excet when the thinners evaporate ( easily re-added) if the pot crystalises just heat it like you would with honey and it's fine to use.
    We rescued some Devoe epoxy tinted pink and mauve in a ships store cleanout it was at least 12 years old. I gave it to a friend who painted the inside of her hull with it and it's perfect.

    That's all I've got to say about that:)
     
  7. CDK
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    CDK retired engineer

    In my opinion, one coat is never enough. A hull is a large surface, there are bound to be some flaws that will be covered by the 2nd layer.

    Anything containing solvents will have pores. otherwise the solvent under the touch dry skin would stay there forever. The 2nd layer will have these too, but probably not in the exact same spot.
     
  8. Landlubber
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    Landlubber Senior Member

    ...I did not mention in ONE COAT.....I was referring to the minimum amount required...and yes, a wet paint gauge is what is normally used.
     
  9. CDK
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    CDK retired engineer

    I know that Landlubber, but I answered part of the original question from MikeWade.
     
  10. rugludallur
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    rugludallur Rugludallur

    Your paint supplier should give you all the numbers

    Any proper distributor who supplies marine epoxy paint for steel should provide you with all the numbers as a consistent system, there are so many factors to consider.

    Professional marine epoxies are applied with airless sprayers, these allow you to spray very thick paint with up to 90% dry content up to 500 microns thick. Any other type of sprayer will need copious amounts of thinner and around 10 passes to achieve that film thickness.

    You should also be thinking in paint systems, not a single type of epoxy and the layers of the system all need to be compatible, for example.

    Above the waterline you might very well want a zinc-epoxy based primer followed by a thick epoxy intermediary layer and finalized with a polyurethane coat.

    Below the waterline you don't want zinc primers so a regular epoxy primer followed by a thick primary layer, a boundary layer so that the anti-fouling sticks and finally the anti-fouling.

    For the deck you might also want to mix some anti-skid silicone dust into the paint or alternatively you can put some high quality garnet/silica sand into the final wet layer of paint.

    I put a few more pointers along with some sample paint systems on my website where you can check it out, it's in the lower part of the page:

    http://dallur.com/index.php?id=16

    Jarl
     
  11. Herman
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    Herman Senior Member

    As a complete side step, as you are in the UK, for deck anti-skid I would suggest using Sicomin / Map Yachting Deck Line paint. This is a rubbery material once cured, nice for (bare) feet and clothing. I believe it is marketed by grptools.co.uk
     
  12. MikeJohns
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    MikeJohns Senior Member

    The non-skid poolside paints are very good on a deck. Galv rich primer then epoxy top coats then the rubberised non skid works very well and I've used it for my own boats for decades. Most of the paints marketed for swimming pools work well in a marine environment.
     
  13. Landlubber
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    Landlubber Senior Member

    Clorinated rubber are the products being referred to above....but we are off topic...
     
  14. GlenM
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    GlenM New Member

    This article/spec sheet will give you an estimate on film thickness for under the water line. I used this system on my Goderich 37 four years ago.
    I would imagine that they want to pull these things out for repairs as little as possible. I also found that a lot of barges, and tugboats use this same system.
    It would probably be best to contact your coating mfg. to get specifics on the coating you are going to use.

    ftp://ftp.dot.state.tx.us/pub/txdot-info/cmd/cserve/specs/1993/spec/es7207.pdf


    Glen
     

  15. bleasdale
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    bleasdale New Member

    epoxy coatings

    this is very simple two coats of epoxy anti corrosive each at 150 microns dft total 300 microns dft followed by 100 microns dft epoxy tie coat followed by three coats of anti fouling each at 100 microns dft on the vertical sides and two coats on the flat bottom this for a five year guarantee,make sure the blasting is good preferably with steel grit and that the climatic conditions are checked according to the paint makers data sheets.
     
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