Subject: how are metals plated?

I put some soder on the negitive termanal and a piece of steel on the other 
postive termainal.  this was in a salt water solution.  when i checked back 
in a hour white stuff deposited on the soder and a grey spongy looking 
stuff depostied on the steel.  i whiped a little of the stuff of the steel 
and soder and found that the soder had been reduced in size an the steel 
just turned a dull grey. what happed?
also sence soder is a lead and tin mixture i understand that it might not 
work to as a plateing.  so, how would I plate steel with zinc then copper?\
thanks -kyle
p.s.  I have knowlege of oxidation redution reations.

Re: how are metals plated?