Homebrew PCBs

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