Chemical equation of a rusting piece of iron in salt water?

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Offline cableguy

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Hi, I've been smashing my head against the desk trying to figure this out, but to no avail. What is the equation of iron rusting in tap water against salt water?

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Offline Supercryptid

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Here's a link you might find interesting: http://corrosion-doctors.org/Experiments/rust-chemistry.htm

And this: http://www.madsci.org/posts/archives/2005-12/1134348446.Ch.r.html

Dissolved salt would act as an electrolyte, the net effect being to speed up the reaction because of the increase in electrical conductivity of the solution.
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Offline cableguy

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Thank you, mate. Got another question, how about if I wrap piece of copper wire around the iron? My experience is the iron would rust faster and I assume that's because iron is more reactive than copper, so it will release electrons easier:
Fe -> Fe2+ + 2e-
But where do the electrons go? Usually, I'd say:
Cu2+ + 2e- -> Cu
That would bring me to the copper's involvement in all of this, but where did the copper ions come from?
« Last Edit: 03/12/2012 23:55:19 by cableguy »

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Offline Supercryptid

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According to the first link, the electrons released by the iron would be consumed by the hydrogen ions and oxygen in solution to produce water.

You may also be interested in this: http://en.wikipedia.org/wiki/Galvanic_corrosion
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