I used to use this years ago to clean beer cans for my collection. It won't work on the heavier stuff (well, maybe with enough time), but it will clean them up. I never had any issues with the paint, but I was warned to try an inconspicuous spot to make sure. After I was done I would clean it off with a solution to neutralize the oxalic acid, then rinse and dry. I can't remember what the solution to neutralize it was, but it was a common kitchen item.