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  1. #1
    ozhunter's Avatar
    ozhunter is offline Quantum materiae materietur marmota monax si marmo
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    Default Odd (to me) ocurrance with Citric Acid

    Hello all

    I have used citric acid quite a bit to remove rust etc from steel, without problems.

    The two attached pictures are of two hand wheels that I've had laying about that were chromed and I wanted to get rid of the chrome, so I put it in citric acid.

    At about the same time, I put some big green shed hinges and steel wheeled castors in a separate container with citric acid. They were both left in the citric longer than I intended.

    Both containers have formed a yellow scale on the steel and yellow sludge in the bucket. The hand wheel bucket is worse than the hinges etc.

    The scale is VERY hard on the hinges and difficult, but not impossible, to remove, with no apparent damage to the steel underneath.

    Any idea what the scale is and is it harmful to me? Suggestions on the best way to remove it and stop it from occurring again?

    Thanks in advance.
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    If you find you have dug yourself a hole, the first thing to do is stop digging.
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  2. #2
    BobL is offline Member: Blue and white apron brigade
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    I'm guessing if the coating was chrome then its Chromium citrate. A lot of what passes for chrome, especially on vehicles is nickel so in that case it would be Nickel Citrate.

    There does not appear to be a lot know about Chromium citrate except that it has been found to have a 50% oral death rate of 15g/kg in rats. In that case and 80kg person would need to eat 1.2kg for a 50% chance of death. 0.25-0.75 mg Cr/kg body weight has been found to be a potentially effect anti diabetic medication.

    I'd say you have no way of preventing that happening.

  3. #3
    ozhunter's Avatar
    ozhunter is offline Quantum materiae materietur marmota monax si marmo
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    Thanks Bob

    It seems to disappear again when you put the items in a fresh batch of citric and give them a scrub with a wire brush. Definitely won't be eating any.

    The hinges would have a coating of a chrome like substance (that's why I put them in the acid, to get rid of it) much like the hand wheels.

    The hand wheels seem to have a layer of copper under the chrome, I discovered today.

    Note to self: Don't leave things in the bath too long.
    If you find you have dug yourself a hole, the first thing to do is stop digging.
    I just finished child-proofing our house - but they still get inside.

  4. #4
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by ozhunter View Post
    Thanks Bob
    It seems to disappear again when you put the items in a fresh batch of citric and give them a scrub with a wire brush.
    Thats handy.

    Definitely won't be eating any.
    The hinges would have a coating of a chrome like substance (that's why I put them in the acid, to get rid of it) much like the hand wheels.
    The hand wheels seem to have a layer of copper under the chrome, I discovered today.
    Note to self: Don't leave things in the bath too long.
    Copper is a common under plate on both copper and Ni.
    Did the copper come off?

  5. #5
    ozhunter's Avatar
    ozhunter is offline Quantum materiae materietur marmota monax si marmo
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    It doesn't look like the copper shifted. I'll know for sure once they are cleaned up. The hinges etc didn't have anything under the zinc coating.
    If you find you have dug yourself a hole, the first thing to do is stop digging.
    I just finished child-proofing our house - but they still get inside.

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