Small rust spots that emerge in chrome bumpers and other brightwork can sometimes be removed with a good polish and lots of elbow grease to buff up the exterior. Quite a few general metal polishes, such as Brasso, are effective, whereas some car metal polishes include a sealant to help protect the exterior.
Excessive corrosion on a car’s brightwork probably cannot be removed just by using polish. Instead, try soaking some fine wire wool in paint thinner, then gently rubbing it over the corrosion. Keep the wool soaked in thinner and don’t rub too hard.
Use a clean cloth to wipe off the dirt, rust residue and remains of the paint thinner to see if the corrosion has been removed. This method may not restore the brightwork, but it will hopefully remove the unsightly corrosion.