Oxidation of Aluminum

  1. mrjeffy321

    mrjeffy321 881
    Science Advisor

    I saw this arcticle on popular science's web site:

    it tells about a way using mercury paste to make aluminum rust, very fast and crumble to dust.

    as you can see in their picture, it apearently is true, and as they explain in the article, the mercury infiltrates the metal and disrupts its protective coating of aluminum oxide, allowing it to oxidize much more compleatly then normal, because its protective barrier is gone.

    if you look at the "rust" around the base of the aluminum bar they destroyed, it looks dark brown or black, which seems odd to me, considering aluminum oxide is while, mercury is silver, and aluminum is silvery. aluminum oxide is extreamly stable and wouldnt want to normally react with the mercury, so why is all that stuff brown? mercury oxides are that color (HgO is yellow or red and Hg2O is black) but why would the mercury be reacting with anything in this instance?
  2. jcsd
  3. chem_tr

    chem_tr 613
    Science Advisor
    Gold Member

    Mercury is greyish black, and amalgams may differ in color. In here, I think the mercury-aluminum alloy (an aluminum amalgam) is quickly oxidized. It "separates" some of the aluminum to react, I think.
  4. mrjeffy321

    mrjeffy321 881
    Science Advisor

    but the paste you put on the surfave of the aluminum can only be put on so thick, and then once it is used up (fairly quickly I would think if the mercury goes directly into the aluminum-mercury allow) then it should stop, fairly quickly. but this seems to go on for hours, or longer it didnt say, and keeps going, I would think the mercury would have long been used up if that is the case.
  5. I'm pretty sure mercury is just acting as a catalyst and remains free after the reaction.
  6. mrjeffy321

    mrjeffy321 881
    Science Advisor

    O, but that doesnt explain the weird color of the "rust" shown in the picture anyway.

    O well, that would be a cool reaction to test if, at least, mercury wasnt so blooming deadly.
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