You can use an eraser to rub off the oxidation. It is cheap, safe, and leaves no chemical. You should use the one for removing ink from ballpoint pen, not the one for removing pencil marks.
Best way of removing rust from silver or other
I have a pair of Audioquest cables with silver banana plugs that have tarnished due to humidity and time. I wonder which is the best way of removing this tarning without damaging the plugs permanently....Btw, is this sort of tarnishing detrimental to sound or just something that is not aesthetically pleasant?