Steel lifespan

Discussion in 'Metal Boat Building' started by SChow, Oct 2, 2010.

  1. SChow
    Joined: Oct 2010
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    SChow New Member

    I hope this is the right forum; I do not plan on building a steel boat, but I do plan on repairing it should the need arise. I also hope it's not too dumb of a question.

    I've heard steel boats have a lifespan in the 25-35yr year range, and after that the cost / maintenance just skyrocket. Is there any truth to this? Hypothetical sailboat in question is 40ft give or take and has been reasonably maintained and is about that age.

    If so:

    Could a skilled welder / dedicated DIYer keep it from becoming cost prohibitive or is it fate?
  2. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    I'd say it's not the age so much as the condition and maintenance level that will limit the economically useful age of a steel boat.

    What kills steel, of course, is rust. A meticulously maintained hull with a good coating system can last almost indefinitely, as long as it's kept properly painted and rust free. It's not uncommon to see steel boats from the '50s and '60s still in service, if they've been kept in good condition and regularly repainted.

    It's probably fair to say, though, that most boats don't get the level of maintenance required to keep them in pristine condition for many decades. At 25 to 35 years or so, there's a good chance that a lot of the harder-to-reach areas will have suffered dangerous levels of corrosion, and of course the engine, tanks and electrics are dying at around this age.

    The way to decide, IMHO, is to find a really, really good metal boat surveyor- fly him in from halfway across the country, if you have to. Spend a full day with him at the boat, poking around in all the hard-to-reach areas, measuring the plating thickness, etc. If it's structurally sound and you're OK with the state of the powerplant and systems, good. If the plating's rusted too thin, the structural grid is starting to deteriorate, etc. then you know you're looking at enormous, ongoing repair bills.
  3. SChow
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    SChow New Member

    Is the situation generally any better with older aluminium boats? Does your average alum boat last much longer?

    I know their main issue is galvanic corrosion, I'm just wondering if it's as bad as the rust issues steel faces, and if fixing up an older alum boat is about the same endeavour is steel.
  4. wardd
    Joined: Apr 2009
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    wardd Senior Member

    steel rusts on contact with oxygen, eliminate oxygen contact eliminate rust

    sealed steel spaces will rust until all the oxygen has been used and the rusting process stops
  5. gonzo
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    gonzo Senior Member

    With proper maintainance any material will last forever. I think that zinc spraying is one way to lengthen the life of your boat.
  6. welder/fitter
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    welder/fitter Senior Member

    Not a dumb question at all. While there are a fair number of very old steel, even iron, boats/ships/marine vessels in our local waters, I would agree with the statement that after 25 to 35 years, the cost of refit goes up significantly. You'll hear some people state that you should carefully inspect the interior of a steel boat well, because steel boats rust from the inside out. While you should certainly inspect inner shell plating, frames, stringers, and other unseen metal components well for results of trapped moisture, not properly primed/painted steel, etc., this isn't the full story. Steel rusts from the inside-out. Not from the inside of the boat-outward, but from the inside of the plate to it's surface layers. "Ad Hoc", "Mike Johns", "Lyndon" and others will be better equipped to explain why, I can only tell you from a shipyard steelworker's perspective that it's a royal pita! The plate can look normal at it's surfaces, but when you cut into it with a torch, you see the metal bubble up & when you hit on the oxygen, molten metal comes back in your face like a shower from hell! When we were re-fitting the ferries, as well as other old marine vessels, you never knew when "the gods would bless you" with such a surprise!(lol)

    You still have to consider fatigue life, of course. All of that twisting & bending for all of those years. less ductility would be worthy of consideration, I'd think moreso with Al, though I'll leave that consideration to the engineers, as well. Mind you, I've seen two late 60s/early 70s steel and one mid-60s aluminum sailboats that "seemed" in pretty good shape. The problem, again, is that one can't always "see" the issues without calling in a tehnician.
    Hope this helps!
  7. Wavewacker
    Joined: Aug 2010
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    Wavewacker Senior Member

    Long ago, I was a mill engineer for a large builder of off shore oil platforms. The legs of the platforms use A-31 grade steel. They are still down there without paint.
  8. Brent Swain
    Joined: Mar 2002
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    Brent Swain Member

    My 31 is 26 years old. Maintenance is about an hour a year.
    The trick is wheelabraded and primed steel , primed with zinc rich primer from the outset, no wood outside, 30 gallons of epoxy tar and many of enamel inside and out, and stainless trim on all outside corners.
    Follow the above and you'll have minimal maintenance , screw up on any one , and it will become a problem.
    On an older boat, where it becomes a problem, sandblast and give her many coats of epoxy tar, eliminate any outside wood and weld stainless on any outside corner, and your problems will be minimized for the next 25 years.
  9. dskira

    dskira Previous Member

    The coal tar epoxy can be a real problem to coat due to the temperature and humidity on steel depending where you are. The anticorrosive effect is between three to five years. Some anticorrosive coat are better suited, like the product from Amercoat here in the US.
  10. gonzo
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    gonzo Senior Member

    Is chlorinated rubber still in use?
  11. dskira

    dskira Previous Member

    As a matter of fact yes. And with success I heard.I never used myself. A friend of mine did it and was please.
    I put the description:
    Chlorinated rubber is a nonrubbery, incombustible rubber derivative produced by the action of chlorine on rubber in solution; used in corrosion-resistant paints and varnishes.

  12. tpierce
    Joined: Feb 2006
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    tpierce Junior Member

    My steel houseboat was built launched in 1963. When I bought it, it was my first "big boat"-40'. I hired a surveyor prior to purchase, and he gave me written report on the overall condition of the boat. I trusted him, as he had been in the business for many years. After buying the boat, I subsequently discovered that it was going to soon need extensive replating throughout an area where most of the plumbing runs were located.

    As stated above, a steel boat will rust from the inside. It's important to have access for inspecting the inside of the hull at regular intervals.

    I started re-plating my boat this summer. It's a dirty, difficult job, but very doable if one has welding and fabrication skills, and the necessary equipment.
    After replacing 4 through-hulls for water intakes, 56 sqft plate, and 36 lf stringers, I have less than 500.00 in materials. It'll cost me 800.00 for complete sandblast of the bottom, and 600.00 for the coal tar epoxy to recoat 2 coats. When done the boat will be good for many years to come. Oh, I also cut out and replaced the entire keel with 1/4" plate.
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