How do you remove tarnish without removing the oxidation from a sterling silver piece?

I have a sterling silver charm bracelet that is oxidized (black over parts of the silver charms to make it look old). The entire bracelet tarnished. Does anyone know how to remove the tarnish without removing the black oxidation? I know not to use a silver dip and also not to use the aluminum foil/water method. I read on a few sites that those methods would remove the oxidation but no where did it state how to properly clean this type of piece. Thank you so much in advance!