How to prevent rust from spreading on trailer

Discussion in 'Boat Design' started by LAURASDAD, Apr 28, 2008.

    Joined: Feb 2007
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    Location: St. Lous, MO

    LAURASDAD New Member


    I apologize if this is not the correct forum for this question. I have a square tube painted trailer with some rust issues.

    I understand the correct treatment is to cut out the rust and weld some iron.

    However, I can't right now.

    Is there a product that will encapsulate the rust to prevent it from spreading? I have also heard of a product that "converts" the rust to metal.

    Any ideas?


  2. dragonjbynight
    Joined: Apr 2008
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    Location: Indiana

    dragonjbynight Senior Member

    I don't know of any product that can reconvert rust to iron, strengthen it temporarily maybe, but would still be eating away at your trailer. How deep is the rust? all the way through? I would say your best bet would be to grind/sand your way through as much as you can then use a rustoleum or similar type pain to cover the area and prevent any more problems. If the rust is deep and the section needs to be welded, I would do it as soon as possible as that will affect the structural integrity of your trailer.
  3. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    At a certain point, new tubing is cheaper than grinding. Sometimes the rust is only surface rust and sometimes it's deep corrosion and the question is whether you own a sand-blaster or a welder because the sandblaster is better if it's surface rust and the welder's better if it's gotta be replaced.
    Maybe you own neither.
    No matter what the condition, if you pay to have the whole thing sand-blasted, you can better assess what has to be built back up when the surface is clean and free of rust.
    At that point, what is okay should be primed immediately and well, and the bad (thin or holed) areas should be replaced. Cut those out with a sawzall or rotary cutter and weld new sections in (or have it welded).
    I highly recommend a Lincoln 135-T mig welder at about $425.00, but there are also some good wire-feed flux-core welders available for half that (you will have to chip away the burnt flux, but the weld is as strong).
    A new trailer would be a lot more and the welder is still as good as new when the job's done.

  4. charmc
    Joined: Jan 2007
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    Location: FL, USA

    charmc Senior Member


    Since you said you can't have a proper cut, weld, and grind done "now", here's a temporary solution. Just understand that it's temporary. The legitimate products that claim to remove rust actually do stop the chemical process that causes the corrosion we call rust ... for a while. At the molecular level there is usually something ongoing, albeit more slowly, so eventually you'll have to do a proper repair. Remember also that chemical coatings do absolutely nothing to strengthen damaged metal.

    You can do a fish plate repair on square tube to strengthen an area (2 steel flat pieces longer and wider than the damaged area, mounted on opposite sides of the square tube and bolted together). It's almost as much work as welding, and it's ugly, but it's a good temp repair if no welder is available.
  5. Petros
    Joined: Oct 2007
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    Petros Senior Member

    There are some rust primers that work fairly well at stopping the rust. I used one on my car that is clear, but reacts with any rust and turns black. You still have to scrape or grind away the loose surface material, and it does not make it stronger ("turn rust to metal"), it only stops the rust.

    If your trailer has rusted through enough to weaken the structure, it is best to repair it by welding and use rust resistant primer to make it last longer for next time.

    Good luck.
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    There are a few products, some aerosol, that can be applied over rust once the loose stuff is brushed away, that will stop the oxidation process. If given a fair amount of prep and a good paint job soon after, then you increase it's life to a degree.

    As has been mentioned, the only real way to stop rust is to grind back to good metal, then prep for a good paint job, which may include reinforcing weakened areas.

    Box tubing trailers are notorious for rusting and are at the bottom of the list for desirable trailer types. C channel and I beam trailers live much long, mostly because they don't trap moisture inside the tubes.

    But you've got what you got and it is a common material to build trailers from.

    A stop gap measure would be to wire brush the loose rust and spray the area(s) with one of those "plasticize" types of rust stopper paints. Then give it a few coats of good finish paint. It'll get you through a season, if you don't have structural issues, like paper thin tubing walls from rust.

    Most trailers are stout enough to accept a considerable amount of rust. The usual failure points are the bolt on stuff, like hubs, axles, spring shackles, rollers, bunks, bearings, tongue jacks, nuts and bolts, U bolts, etc. You can replace these bits and pieces as time and budget permit.

  7. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    As an owner of a homemade box section trailer, I can vouch for their rusting ways. I had to throw away half the trailer recently.

    The trouble is, you never know how far the rust has gone till it breaks - and that may be at an invconvenient time.

    I "got around" the problem by welding a heavy duty L channel on the bottom outside of the square section. It was strong enough to support the section by itself, so the square section can rust as much as it likes.

    In essence, the square section just acted as a handy *mould* for the L channel, and I will just knock and grind the square section off the L channel when it rusts far enough to justify the effort.

    At least it wont fall in half on the highway.
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