the plating may have been damaged by the leaking cell(s) but Deoxit can help.
Try Deoxit brand cleaner,
litle expensive at first glance but only the
smallest drop is needed.
Great on older tube style radios and the bandswitches too.http://www.deoxit.com/
MCM p/n 200-195
Deoxit p/n DP5S-6
this is the pump spray version, so no
hazmat ship fees.
Fry's also carry it in the stores.