Just like what drives pretty much everything in this universe, entropy.
The copper ions in solution are more electronegative than aluminum
metal. As a result electrons are transfered from aluminum to the copper
ions. The copper atoms become neutral (metal) and the aluminum atoms
become ions (dissolved in solution).
Why is your experiment be a failure?. You clearly determined the answer
to your question if ferric chloride can turn an aluminum surface black.
lcdpublishing wrote:
> Hi guys,
>
> Perhaps one of you chemistry guys knows what happened here. While
> etching a board, I got to thinking about how the Ferric Chloride
> stains some metals (and wood, and other things) black. Always one to
> try things, I dipped an aluminum bar in the stuff for a few seconds.
>
> When I pulled it out, it had what appears to be rust scale on it like
> crazy! I assume this to be bits of Copper and not rust, but I was
> wondering if someone could explain what happened there? I don't think
> it was electrolysis - no electricty going through the mess.
>
> Yet, somehow, the copper seemed to attract to the aluminum - it didn't
> stick though. A rinse in water removed it quickly. The aluminum did
> turn gray in color and not black like i had hoped - so it was a failed
> experiment. But, it sure was interesting and raised a few questions!
>
> Chris
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