I did once. I had nothing else and wanted to see how a heavy link
chain would look oxidized. I had bleached a pair of denim jeans a
long while ago, and I remembered that the bleach I diluted in a
bathtub full of water had turned my silver ring black. ( At the
time, I was not amused.) The chain I oxidized is still black, but I
had to polish the outside of the chain that comes in contact with my
skin, because my skin turned black too. I don’t know if I "oxidized"
the chain, but some kind of chemical reaction definitely took place.