OT/OFT Batteries and Pennies

[ggehrke at gmail.com (GGehrke)]

I was going to go to my chem books and look it up exactly, but it's
been pretty well explained.  It's all just about the interface between
the two metals and which is higher in the activity series than the
other.  The reactivity of the metals compared to each other (zinc,
copper, whatever's in the terminal, etc) will determine which gives
electrons to the other and where deposits and such form.  Either way,
corrosion will take place, and often placing two dissimilar metals
together will accelerate corrosion, so whether you're getting the
typical blue crusty junk in the same place or not, metal is being
attacked and corroded away.  Copper is pretty high in the series, so
it will usually take electrons, which confused me for a bit, but I
think the zinc in pennies, as someone else already pointed out, is the
key.  The navy uses zinc sacrificial anodes on our ships for that
reason, but they have to be replaced periodically because they get
used up, so I wonder too if the penny would disappear after a while.
For that reason, I'd rather just cover it with a plastic cap or
dielectric grease.  Remember, too, that corrosion will not take place
if there isn't air/moisture reacting as well.  If you can seal them
off, no corrosion.  The hydrogen gasses released from the battery
itself when it charges are not particularly helpful either, so sealing
the terminals off from the gas would seem to me a much more
appropriate solution.

-Grant-