On my 1990, the fuel filler is starting to rust on the wheel well side.
This filler, has the filler metal (with the flap, etc) bonded somehow to the plastic pipe.
Inside, under the cap, appears to be inbperfect shape.
I'm planning to wire wheel the metal, but I'm not sure what paint to use.   In other projects, tremclad paint, for example, did not survive contact with gasoline at all.