Reworking an old steel barge

Discussion in 'Metal Boat Building' started by sisotowbel, Oct 30, 2011.

  1. sisotowbel
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    sisotowbel New Member

    I'm about to commence work removing rust from a heavily corroded dutch barge.
    I want some advice concerning methods...

    First, I'm working on the outer hull above the water line.
    I plan to use a needle scaler on scaly rust under the scuppers and flat surfaces,
    also a cup brush/wire wheel on an angle grinder for the flat surface.

    I then plan to use rust-con, before coating with red oxide, and finally top-coat.

    Does anyone have any alternate methods to suggest, or views on mine?

    Thanks,
    Will.
     
  2. Nick.K
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    Nick.K Senior Member

    If the corrosion is wide spread and the barge is as large as some I´ve seen then your method sounds like a huge ammount of work.
    Sandblasting followed by epoxy (jotamastic?) would be far quicker with better results...but I guess you are in a residential area?
    All the best
    Nick.
     
  3. MikeJohns
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    MikeJohns Senior Member

    Read this thread and particularly my comments here:

    http://www.boatdesign.net/forums/me...erior-rust-steel-hull-35236-6.html#post475125

    Good quality Pneumatic Needle-Guns/descalers are good but they don't work very well on thinner plate (LT 6mm) away from frames. De-scale grind and then more selectively de-scale, or sand blast and get it over with. It depends on the pattern of corrosion, it could be anything from light scale and surface rust that cleans off with a grinding disk to heavy pitting and entrapped scale.
     
  4. michael pierzga
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    michael pierzga Senior Member

    Yup...just as MJ states , mechanical preparation...needle guns, brushes, grinders... are effective and logical is you dont have access to a sandblaster. For paint Ive had good luck with Devo Bar Rust...its a surface tolerant paint. Be sure that your steel surface is completely grease oil free before beginning any surface preparation

    http://www.international-pc.com/PDS/4321 P eng-usa LTR.pdf

    By all means investigate the possibilities of blasting. It is the most effective.

    Locally blasting is prohibited unless the boat is completely tented, hence its expensive for normal folks.
     
  5. gonzo
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    gonzo Senior Member

    A needle gun followed by a sand blaster would be the standard method.
     
  6. rsimon
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    rsimon Junior Member

  7. rsimon
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    rsimon Junior Member

  8. welder/fitter
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    welder/fitter Senior Member

    You didn't mention size of barge or amount of corrosion, although you did mention "heavily". As previously mentioned - several times - sandblast it. needle-guns are great for tight spots & grinders will cover areas more easily, but better to strip it right down with a blaster for large areas. put a coat of red oxide primer on before you start your cut-outs, but check carefully for pinholes & thin material before laying on the primer.
     
  9. gonzo
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    gonzo Senior Member

    If the corrosion is very heavy, there will be structural damage. Also, there will probably be pinholes that leak.
     
  10. Yobarnacle
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    Yobarnacle Senior Member

    Needle gun, haha. Only good for tight crevices and hard to reach areas. This is a F**Koff tool for lazy deckhands. They can sit on a bucket in one spot and mindlessly rattle all day. A rotary scaler is 10 times faster, but heavier and you need to pay attention using it. Waterblasting is best and is used in shipyards. Epoxy bonds very well with the thin film rust that forms afterward. Grit can be added to the water medium if necessary.
     
  11. MikeJohns
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    MikeJohns Senior Member

    For sure a needle gun is not the tool for stripping large areas of deck, but a good random needle gun driven by a large enough compressor is a very useful tool.

    Rotary scalers usefulness is limited to flat surfaces and they cannot access the corners, nooks and crannies that a needle gun can. Usually the worst pitting is where the paint film changed direction by 90 degrees and cracked.
     
  12. Nick.K
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    Nick.K Senior Member

    Mike. From interest. What is your view of epoxy bonding to flash rust after warte blasting?
     
  13. MikeJohns
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    MikeJohns Senior Member

    How much rust?

    Usually after the waterblasting rust bloom it's worth lightly sanding and wiping the area with any evaporating thinners, even a kitchen scouring pad will largely remove it .
    rust powder doesn't have a high bond strength and even powdery rust reduces the epoxy bond to the surface, rollers and spray don't disrupt the small rust particles but mild mechanical scrubbing does aka work :).

    when you apply the epoxy the hull must be absolutely dry and as a rule of thumb if you dampen part of the hull with a cloth or sponge the water should all evaporate within 1 minute. Do it where you have integral tanks and large masses of material like ballast. These are where light condensation really wrecks the epoxy bond. Otherwise hire a big LPG heater !
     
  14. Yobarnacle
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    Yobarnacle Senior Member

    UNFORTUNATELY, your remarks run counter to marine coating manufacturers recommendations. All I queried over the years recommended allowing a light rust to form before applying the epoxy. It's a better tooth they say. I'm referring to very expensive large paint jobs on vessels hundreds of feet long.
     

  15. Yobarnacle
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    Yobarnacle Senior Member

    to explain further, of my 43 years plus at sea, I sailed as captain more than 30 years. Companies with fleets don't buy paint for a single project. They contract with a coating manufacturer for the whole fleet. The manufacturer always sends a representative to oversee the application because there are guarantees in the contract as to longevity of the coating, and because a disatisfied customer is losing an entire fleet and big bucks. I always conferred with these company reps, as to maintenance and coating repair, as well as application. Hence, my comment that epoxy primer likes lightrust. Something else to think about regardind tightness of rust films. Gun bluing is a controlled rusting process. Imagine that!
     
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