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Thread: Steel CB protection

  1. #36
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    Sound Beach, NY
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    Default Re: Steel CB protection

    I've had two boats with iron keels. Both were primed and painted originally and held up well. On one I scraped scaled and sanded it by hand, primed with zinc paint, and copper bottom painted. That was over 20 years ago, it still looks good. I have no doubt that galvanizing is best, but many thousands of steel ships travel the world with no more than paint and primer on the hull. Many many classic boats have iron keels that are just painted too.

  2. #37
    Join Date
    Oct 2008
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    Walney, near Cumbria UK
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    Default Re: Steel CB protection

    Quote Originally Posted by johngsandusky View Post
    I have no doubt that galvanizing is best, but many thousands of steel ships travel the world with no more than paint and primer on the hull. Many many classic boats have iron keels that are just painted too.


    Cast iron ballast keels and mild steel corrode at vastly different rates.
    It really is quite difficult to build an ugly wooden boat.

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  3. #38
    Join Date
    Jul 2011
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    Lindstrom, MN
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    1,915

    Default Re: Steel CB protection

    Don't forget the zinc anodes or impressed current systems on those thousands of ships:
    Quote Originally Posted by johngsandusky View Post
    I have no doubt that galvanizing is best, but many thousands of steel ships travel the world with no more than paint and primer on the hull. Many many classic boats have iron keels that are just painted too.
    Quote Originally Posted by Peerie Maa View Post


    Cast iron ballast keels and mild steel corrode at vastly different rates.
    This links to a pdf that has the results of testing done on zinc rich primers, followed by tests on rust converters.

    Zinc rich paints:
    1. Zinga Organic epoxy primer 96% Zn
    2. Zinc Clad IV Solvent-based 85% Zn
    3. Zinc Clad XI Water-based inorganic Zn silicate with no VOC and 90% Zn
    4. N-5751M2 Solvent-based moisture cure 90% Zn
    5. Intershield 300V Aluminum-rich epoxy
    6. Epoxzen Organic epoxy with 90% Zn

    Rust converters:
    1. Gempler’s (water-based, tannic acid)
    2. Loctite rust treatment (polymeric-based, barium sulfate)
    3. Total Solutions (water-based, tannic acid)
    4. Phoscote (phosphoric acid – current USMC product) <>>
    5. VpCI CorrVerter (combined rust converter and primer)
    6. Corroseal (water-based, tannic acid with primer)
    7. Gem Rust Killer (under test)
    The rust converters were coated with a non-corrosion inhibiting epoxy primer and a polyurethane topcoat. While they are good paints, there was no chance that the rust converters would look good in these tests. It is unfortunate that they didn't compare to a sample without a converter. All I can say is that none of the rust converters looks bad, since all they do is help the paint stick to the metal.
    Last edited by MN Dave; 04-16-2018 at 11:52 AM.
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  4. #39
    Join Date
    Jun 2006
    Location
    Blacksburg, VA
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    391

    Default Re: Steel CB protection

    Quote Originally Posted by ahp View Post
    Idle curiosity. US submarines are black.. What do they use, or are they telling?
    Secret submarine stuff aside, hot-dip galvanizing an entire steel ship is not possible. Instead, they are protected with zincs that work on the same principle.

    I wonder if you could design a steel centerboard with a protective zinc?
    I will beg you for advice, your reply will be concise, and I will listen very nicely and then go out and do exactly what I want! (Apologies to Lerner and Lowe.)

  5. #40
    Join Date
    Oct 2008
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    Default Re: Steel CB protection

    Quote Originally Posted by alkorn View Post
    Secret submarine stuff aside, hot-dip galvanizing an entire steel ship is not possible. Instead, they are protected with zincs that work on the same principle.

    I wonder if you could design a steel centerboard with a protective zinc?
    The bilges of warships used to be flame sprayed with zinc, nearly as good as hot dip.
    As to you question about designing a cb with a protective zinc, That is what we have been recommending - hot dipped.
    It really is quite difficult to build an ugly wooden boat.

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