I have a set of Mini Monti's in Blue Steel. IT is not immune to corrosion occasional cleaning with flitz will keep them nice.
Like guns, even other cups, copper, brass, bronze the metal needs to be maintained. I have the first set of BGS Phoenix cups from
about a year ago and with about 5 applications of flitz they look as good as the first day I flitzed them.
BGS is prone to some rusting, the same way a gun is, but maintaining them with either flitz or wax will protect them quite well.
Jake