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Oxalic Acid- rust remover!

vinny Feb 28, 2008

  1. vinny

    vinny Senior Member

    Doing my browsing again!
    Found this tip about cleaning rust from a petrol tank -

    Rust is easily removed with Oxalic acid. It can be found in your local hardware store, labeled as wood bleach. It comes in a plastic tub. You mix the granules with hot water and simply soak the rusted item's in it. I have used it in a fuel tank to remove even thick scaly rust. It seems to only have a harsh reaction with the rust itself. If left on a painted surface it can discolor it. Clean metal seems to be unharmed by the solution. After a couple hours of soaking, I neutralized the surface with a baking soda solution and rinsed with plain water. Remember it is acid, so read the warning label.

    Apart from rinsing with water - may be better to use old petrol to flaush? :detective:
     
  2. tmdoth

    tmdoth Senior Member Supporting Member

    If you plan on using old petrol to flush out the acid, you would have the check the reactivity of alkanes with strong weak acids. From I can figure out, it might be a bit of an issue as gasoline is a non-polar hydrocarbon and oxalic acid is a non polar acid. As like attracts like, there is the potential for a reaction between the two chemicals. It could be as simple as having them combine and both be flushed out, or you could run the risk of forming precipitates inside the gas tank and having a hard time getting them out. More unlikely but possible is that they could, in combination, have a high reactivity and form a noxious gas. As oxalic acid is already an irritant it could be pretty nasty. I would reccommend that if you still plan on going that route, that you do a small test in a slightly rusty cup or something and see what happens. Or just stick with water, with its polarity it shouldn't react very much at all with the acid other than to possibly dilute the solution; either way it should all come out of the tank without any residue being left behind. Plus gasoline is highly combustible in the wrong environment and just adds to the possible dangers.
     
  3. vinny

    vinny Senior Member

    Thanks for the response TMDOTH, I had considered using the old petrol to flush - because i didnt want to have the "flash rust" undoing the cleaning. :blackeye:
    But I am certainly going to use water now - don't want to risk obnoxious gases etc.
    Thanks again. :D
     
  4. Bacchus

    Bacchus Senior Member Supporting Member

    ever try this to clean rust off rims?
     
  5. tmdoth

    tmdoth Senior Member Supporting Member

    Nope, but from what I have read about it it should be fairly effective for that application. There are slightly stronger acids that are available that could do a better job, such as phosphoric acid, but it really depends on how caustic an acid you want to use. Oxalic acid might take a few passes but it will definately get the job done. Just try to stay from any paint or rubber.. not very good for them.
     

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