Ferocement soaked with diesel

Discussion in 'Boat Design' started by Chuck Losness, Jun 24, 2011.

  1. Chuck Losness
    Joined: Apr 2008
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    Chuck Losness Senior Member

    Hi all,
    A friend just hauled his ferocement sailboat and discovered that his diesel tank had been leaking and a small portion of his hull is saturated with diesel. It is saturated all the way through the cement and diesel is dripping off the bottom. The primary solution being proposed by yard is to saturate the affected area with acetone. The thought being that the acetone will displace the diesel and then evaporate leaving clean cement that could be sealed with epoxy.
    Anybody have any ideas on how to solve this problem.
    Thanks for your help.
    Chuck
     
  2. CDK
    Joined: Aug 2007
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    CDK retired engineer

    That will not work!
    Acetone doesn't displace diesel fuel but mixes with it in any ratio. If the cement is porous (that seems to be the case) the acetone will evaporate at the surface but the heavier fractions of the fuel will stay there.

    Soak the inside area with engine cleaner, that is white spirit with a detergent, then flush with lots of water until all milky traces have gone. Then brush or pour waterglass (sodium silicate) over it and let it dry. Repeat the waterglass treatment until the surface doesn't absorb more fluid.
     
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  3. Poida
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    Poida Senior Member

    In my humble opinion if dieseline was a problem with concrete, every workshop around the world would have a problem.

    In my simple mind, I would assume that ordinary workshop degreaser would be the answer.
     
  4. CDK
    Joined: Aug 2007
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    CDK retired engineer

    The problem is not the diesel fuel itself but the fact that it reaches the outside surface, so the hull is porous and probably always has been. You could use degreaser to remove the fuel, but that would also migrate through the concrete so you'd need a lot of it to remove the greasy fuel before you can seal the ferrocement.
     
  5. Chuck Losness
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    Chuck Losness Senior Member

    Thanks for the suggestions. I will pass them on to my friend.
    chuck
     
  6. MikeJohns
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    MikeJohns Senior Member

    Light oil does soak through the plaster over time.

    It is actually considered a serious issue with ferro cemnt hulls. When the wire mesh is zinc coated the zinc quickly reacts with diesel oil and turns into a grey sludge. The bond between the mesh and the plaster is destroyed and the hull become a lot weaker in that area. Once the cement is saturated it's very hard to get it out.

    Diesel fuel has always been a problem with ferro-cement hulls and they should be well epoxied inside integral fuel tanks.
     
  7. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    How big is the saturated area?,(you said a small portion of hull) i have encounted the same issue with a wood Grand Banks trawler and just replaced the saturated planks. It would not be a real big deal to knock out the saturated plaster, leaving the mesh intact and then re plaster it. I dont see much sucess with solvents or detergents. Either way is going to take a fair bit of elapsed time but re plastering is going to have a known outcome, the other, not so much.
    Steve.
     
  8. Chuck Losness
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    Chuck Losness Senior Member

    The saturated area is along the front edge of the keel. I don't think that re-plastering the effected area is a viable option. The yard has no experience with that and neither does the owner. Trying to get the diesel out and then epoxy sealing the area appears to be the only option.
     
  9. Mckruger
    Joined: Jun 2011
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    Location: South Africa

    Mckruger Junior Member

    Diesel saturated area

    Hi Guys, I have been involved with the brewing of bio-diesel from sunflower oil and foune that sunflower bio-diesel is a very good solvent for mineral diesel. If you could getr some and use that to remove the mineral diesel first, the biodiesel is easy to remove with a soap mased solvent.
     
  10. Ilan Voyager
    Joined: May 2004
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    Ilan Voyager Senior Member

    The ferro-cement looks very porous or worst cracked. It will be impossible to remove the soaked diesel, and soon or late the remaining diesel will come to he surface again, peeling out any surface treatment.

    Plus the affected zone -"The saturated area is along the front edge of the keel"- may have some structural importance. There are stresses concentration in this place, with a sharp variation of surface geometry and mechanical inertia.

    I would make a very serious survey of that to be sure that the boat is not affected structurally by the "porous" cement impregnated of diesel. I'm not convinced that the cement is adhering now to the mesh, and probably there are hairline stress cracks (that would explain the diesel appearing on the outer surface, I can't imagine that a correctly made ferro-cement is so porous...).
     
  11. tunnels

    tunnels Previous Member

    Important to seal only one side of the concrete (Outside)and dont cover the inside with anything what so ever . !!
     
  12. sdowney717
    Joined: Nov 2010
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    sdowney717 Senior Member

    is there any hope of smashing out the oil soaked and cracked concrete and replacing with new cement?
     
  13. Frosty

    Frosty Previous Member

    So you being advised by some one that does not know the answer.

    I would cure the leak, clean it up, check for cracks, if none found, paint the underneath with the appropriate sealer and antifoul and leave it.
     
  14. Chuck Losness
    Joined: Apr 2008
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    Chuck Losness Senior Member

    Here's what they did to supposedly solve this problem according to the owner.
    The outside was cleaned several times with acetone. When the diesel finally stopped dripping (I don't know for how long) and they got hull dry (I don't know how they determined this) the exterior plaster was coated with epoxy and bottom paint and the boat is now back in the water. The owner is satisfied with the repair. He intends to "watch it" to see if anything adverse develops.
    So that's where it stands at this point. Thanks to everyone for their suggestions which were passed on to the owner.

    Chuck
     

  15. Ilan Voyager
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    Ilan Voyager Senior Member

    It's just a cosmetic work made after a bet on the future of the boat.
    The problem has not been solved as there is diesel remaining in the cement, probably making now its way along the mesh.
    So nobody has an idea of the structural integrity of the boat just in front of the keel, one of the most stressed parts of a sail boat.
    I won't make further comments about this way of thinking and working...
     
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