uh-oh. here we go again.

> What's you chemistry cut on bi-metallic corrosion, electrolyte, zinc, time,
> and what ever....

corrosion has to do with how easy (or hard) some metal (or alloy) will
give up (or receive) an electron. But it is relative to something... So
copper will deteriate in the presence of iron (hence you can't have copper
to iron connections in plumbing without brass in between).  Some solutions
will speed up or slow down the process.  Like Iron and Salt Water. Bad
combination. This 'solution' part (aka 'electrolyte' - something that will
transport electrons in solution, like salt water ).

So with the addition of zinc to an iron system (say a hot water heater
where the water is the electrolyte ). The zinc has a larger desire to
loose the electron as compared to iron, so the zinc will win and loose
it's electron.... (more happens, but that is enough for today)

This stuff is pretty rusty to me, so give me a break... But the idea and
chemistry of a sacrificial electrode is very real and can be useful.  Now
will one chunk of zinc be enough to keep your bus from rusting??? I don't
know.  What i'd do is set up the experiment... Get some zinc, some power
and see which one corrodes faster. Should be pretty easy to set up. Take a
bar of zinc and a bar of iron, put say 3V DC across them and suspend them
in a slution of table salt and water. See what happens. Then reverse the
leads and try again.  Hmmm, science fair project for some kiddies on
the list????

Well, that is about it for me for right now... why don't we get questions
about optics, lasers and molecular dynamics. Things i can answer without
having to open a dusty text book!?
Cheers
Matthew