I have a license plate holder/gas access door that bolts to the rear bumper of a 60 s era muscle car. The door is in excellent shape. It looks like it was originally galvanized. The only rust is surface rust where it appears water leached on to the surface, and one 4″ line that appears to have had something lie directly against the galvanized that iteracted with the galvanized and allowed surface rust to take hold. Two questions. 1. what do you reccommend to remove the rust without removing the galvanized? 2. Any suggestions for refinishing the galvanized?