IBM uses a dilute phosphoric acid solution, as does HP.
Good old Navel Jelly, orthophosphoric acid, seems to be at the heart of a
LOT of products. Nasty stuff if you get it on the wrong thing, but in
general it works great on corrosion.
Personally I still have RED and Blue cans of Cramolin, and a few other
contact specific cleaners and restorers.