I am fixing up an old Nishiki for a friend of mine, and today was using my rotary tool with a soft brass brush fixing to remove some of the tougher crud on the chainrings. That seemed to work pretty well, so I used the same method to remove some rust and crud on the seat post where it had been clamped in the frame for years. Once again, that seemed to work pretty well and also left a nice polish behind. I thought that looked pretty nice, so I polished the whole seat post followed by the stem. They both look nice, but now I'm pretty sure that I should have learned something about polishing metals before I went that far. From a Google and BF search it appears that I may have just made those parts more prone to tarnish in the future. Is that so? If it is, is there anything I can do short of replacing the parts? The brush didn't leave any noticeable scratches on the metal.