Oxidation of Aluminum

  • Thread starter mrjeffy321
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  • #1
mrjeffy321
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I saw this arcticle on popular science's web site:
http://www.popsci.com/popsci/how2/article/0,20967,693558,00.html

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?
 
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  • #2
chem_tr
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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.
 
  • #3
mrjeffy321
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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.
 
  • #4
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I'm pretty sure mercury is just acting as a catalyst and remains free after the reaction.
 
  • #5
mrjeffy321
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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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