Fusionfire
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Gallium + water vs. iron
Hello folks,
It is known that gallium can attack aluminium and chemically activate it to produce hydrogen gas with water.
Iron normally produces hydrogen gas from steam. If exposed to gallium, can it react with water at room temperature to release hydrogen gas? How fast
is the reaction? Does it work against all steels?
Thanks & have a great weekend!
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LanthanumK
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Iron does not have a significant passivation coating like aluminium that can be removed by gallium. The gallium alloy may increase the rate of attack
of ordinary rusting process, but it shouldn't react with water. I can try it though with a bit of galinstan on iron wire. The most likely result will
be gallium embrittlement.
hibernating...
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Adas
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Fe + H2O ----> FeO + H2
This reaction proceeds slowly at RT even without catalyst.
Rest In Pieces!
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Endimion17
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Gallium is not a catalyst in the reaction of aluminium with water. It merely serves as a very tiny obstacle to the formation of aluminium oxide layer.
Catalysts enter the reaction. Gallium does not, just like mercury when rubbed into aluminium.
The iron situation is different. Neither can gallium/mercury penetrate it, or anything happens in particular. It just turns to iron(II) oxide
extremely slowly at standard conditions, and quite quickly at several hundred °C, which is how Antoine Lavoisier made hydrogen after Henry Cavendish
recognized it for the first time. It's not rusting in a usual meaning of the word. Rusting requires oxygen, too.
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weiming1998
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Trying to remove the iron oxide layer via a strong acid gives the same results as gallium rubbed onto the iron. Even if the iron doesn't have the iron
oxide layer, the reaction with water is extremely, extremely slow at room temperature. It might rust in water, but that is because the O2 and CO2
gases in there are oxidizing the iron, forming Fe2O3 and FeCO3. You can try completely submerging it in a saturated salt solution ( to remove the
oxygen, which might react with the iron first.} for a long time.
I remember that in my primary school, we did an experiment on submerging an iron nail completely in salt solution (not even saturated). Absolutely
nothing happened after a week, so that in order to see any visible results, you'll have to leave it there for months or years. Boiling salt water
might be faster, but who has the fuel to keep something heating for days and days (unless solar-powered)?
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Fusionfire
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Thanks guys. I found this article after searching for "gallium steel" instead of "gallium iron"
http://www.springerlink.com/content/v54362923t017768/
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We have investigated the effect of liquid gallium on type 316L stainless steel (as a candidate for the P–V–T pressure vessel), and four
thermoplastics: two semicrystalline (high-density polyethylene and polypropylene) and two amorphous (polystyrene and poly(methyl methacrylate)).
Specimens were coated with gallium and held at elevated temperatures and reduced pressure for extended periods. Measurements conducted on the plastics
include weight change analyses, tensile tests and particle diffusion analysis using dispersion X-ray spectroscopy. For the stainless steel specimens,
tensile and corrosion tests were conducted. Scanning electron microscopy was used to determine the level of corrosion. The results are compared with
specimens heat treated identically but without gallium contact. After 3 months, the gallium corroded the surface of the steel to a depth of only 12
mgrm. No penetration path of the gallium into the steel has been observed. The gallium was also found to cause no change in the mechanical properties
of the polymers tested, nor was it found to have caused any weight change in the specimens. |
[Edited on 25-2-2012 by Fusionfire]
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Endimion17
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If you submerge clean iron unexposed to oxygen in an oxygen-purged water and seal that under argon, nothing visible will happen at standard
temperature probably for thousands of years, maybe even a lot more. That is the reaction of iron with water.
The rate of:
Fe + H<sub>2</sub>O -> FeO + H<sub>2</sub>
is extremely slow.
Rusting, however, is a completely different reaction and involves the formation of local electrochemical cell using areas more or less
saturated with oxygen. Pure iron rusts like hell in those conditions. Pile of powdered iron can even ignite if wet.
The rate of aluminium+water reaction is very quick, but the oxide layer comes into way. Gallium/mercury merely disrupts that layer. If the layer was
not forming, we would keep aluminium in argon, much like rubidium/caesium.
Regarding gallium and iron, I doubt gallium does anything to iron.
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LanthanumK
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Quote from Wikipedia: "Gallium, for example, diffuses into the grain boundaries of Al/Zn alloys[1] or steel,[2] making them very brittle." So it
should make iron (steel) brittle.
hibernating...
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Bot0nist
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That seems in contradiction with fusionfires source...
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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bahamuth
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It appears to be several iron alloys that exibit embrittlement by action of gallium, though I find mixed statements about the embrittlement of pure
iron or steels. It may be that gallium only diffuses into ferrous alloys that contain metals with which gallium can embrittle.
Embrittlement of Ferrous Metals and Alloys (Page 52)
Though I can't find much of the chemical resistance of iron/gallium alloys it is clear that it would not release hydrogen by reacting with water in
such a fashion as the Al/Ga alloys does.
I would not store gallium in metal/iron containers, not just because the potential alloying that can occur but also since the freeze/thaw cycles would
expand and eventually break the metal container due to the increase in volum of the gallium going from from liq. to solid.
Any sufficiently advanced technology is indistinguishable from magic.
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