I've been trying to clean up 50+ year old Westwood rims. At this point, I'm not even certain if they're stainless steel or chrome plated. In the "valley" where the brake pads contact the rim, there is this blackish deposit that I'd like to remove (I think). I've tried a brass brush, steel wool, the steel brush on my power drill, navel jelly, various solvents and nothing seems to take this crud off! All my efforts just seem to shine it up. Is the chrome worn away! Is this some special coating that I don't know about? Should I leave well enough alone?