wish i had a kraken!!!
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Does anyone know what type of reaction takes place here ?
Please check the video here : https://www.youtube.com/watch?v=5Qc_Sy6IAlI , (someone dissolve a spoon in a solution and then put his /her hand in the solution without being
harmed !) , some say he used Gallium spoon and its not steel ! the guy himself claims it is an alloy of Aluminium+Gallium but why there is a reaction
which produces bubbels ? and does anyone know what the composition of this alloy might be?
[Edited on 7-2-2015 by wish i had a kraken!!!]
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Zombie
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Gallium... Aluminium
https://www.youtube.com/watch?v=JasZ8V6LpbQ
Or you just saw SuperMan on Ytube.
https://www.youtube.com/watch?v=UN3bHBTSaHQ
[Edited on 7-2-2015 by Zombie]
[Edited on 7-2-2015 by Zombie]
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wish i had a kraken!!!
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Its not Gallium , It produce bubbels , he says it is an alloy of Aluminium and Gallium(I know Aluminium itself reacts with bases like NaOH, KOH , etc
... and produce hydrogen bubbles ) but the guy claims Gallium makes Aluminium to act more reactive with water , is it possible why? how about other
elements ?
[Edited on 7-2-2015 by wish i had a kraken!!!]
[Edited on 7-2-2015 by wish i had a kraken!!!]
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Zombie
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Look back up. Gallium... Aluminium.
The reaction is caused by the Aluminium IN the Gallium. Aluminium will normally react with water when passivization is prevented. That is what the
Gallium does. It prevents passivization of the Aluminium.
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wish i had a kraken!!!
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Do U know any other elements which cause the same effect when they are mixed with Al?
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Zombie
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Lots of elements, and compounds react in combination. Aluminium is a highly reactive element. It is the oxidation layer that prevents it from reacting
most of the time. Remove that layer, and prevent it from reforming, and that is the true nature of the element.
Look on Utube for Aluminium Reaction. There are Lots of cool vids.
The smart fellas here can explain the chemistry behind what happens. I can tell you how to find cool stuff around the net.
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wish i had a kraken!!!
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I know Al is a highly reactive element , but I want to know in which way Gallium changes Al which stops Al from forming its passive layer ? and what
other types of elements can do the same ?
[Edited on 7-2-2015 by wish i had a kraken!!!]
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Zombie
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You'll have to wait for the real chemist kinda guys to answer that. I'm just the pool boy.
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j_sum1
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A similar thing happens with Hg. I am not sure about other alloys.
Two things happen. The Ga or Hg diffuses quickly along the grain boundaries, weakening the structure and leaving individual aluminium grains. One
way of thinking of it is that you effectively get a Ga-Al or Hg/Al alloy in between all of the grains; effectively weakening it.
The second thing is that the Ga or Hg is able to penetrate the Al2O3 coating. It is then able to form a alloy on the surface of the aluminium. That
alloy does not have a passivating oxide** and so effectively the Al is exposed to the full oxidising nature of the atmosphere.
So the combined effect of weakened structure, increased surface area and lack of passivation causes the Al to deteriorate very quickly.
Observe this two hour time lapse of mercury attacking an aluminium i beam.
**
The requirement for passivation is that the oxide formed occupies the exact same surface area as the parent metal when produced in the appropriate
stiochiometric ratio. In other words, the oxide effectively locks onto the parent metal with the same lattice dimensions.
If the oxide lattice is greater than the parent metal then the oxide will flake off. This is true of most forms of rust.
If the oxide lattice is smaller than the parent metal then it fails to cover the surface fully and new metal is continually exposed.
If the oxide lattice is exactly the same, then any damage to the passive layer will self heal. I know of no better passivation than the one that
occurs on aluminium, although titanium is also pretty good.
Certain chemical reactions can attack the passive layer and prevent this self healing. The presence of Cl- ions is the most common of these. Al
will pit in the presence of chlorides. I believe something similar happens in aqua regia to allow the Au or Pt being dissolved to be continually
attacked.
Certain alloys can be devised to allow an otherwise reactive metal to form a compatible oxide layer. Stainless steel with a minimum of 12% Cr is the
classic. The Cr alters the lattice spacing in both the metal and the oxide and the result is a passive layer compatible with the substrate.
The reverse happens when Al is exposed to Ga or Hg. Now you have an alloy that prevents the formation of a compatible passive layer.
In the case of Al, I am not sure what other elements will have the same effect. From a kinetic standpoint, It believe it is significant that both Hg
and Ga have very low melting points. It might be that no other elements are quite as destructive to Al as these two are.
A good experiment would be to mix up an Al-In alloy and see how it behaves when cooled to ambient temperature. It might be quite susceptible to
corrosion.
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