I picked up a used stainless steel sink for the garage off craigslist. It's a high quality piece and looks great. However there is a stubborn stain on it from what looks to be a water valve leaking over time. It had slight surface rust over the stain that came off easily.

Anyhow, I've tried everything short of sandpaper to remove this mark (Bar Keepers Friend, metal polish, mothers metal polish etc.). You can't feel it on the surface whatsoever.
Got any suggestions on what to try?

Anyhow, I've tried everything short of sandpaper to remove this mark (Bar Keepers Friend, metal polish, mothers metal polish etc.). You can't feel it on the surface whatsoever.
Got any suggestions on what to try?


