I have one small spot of rust. This summer I sanded and painted the surface over--but it is right back. It is the tailgate sill where the metal has a seam on the driver side right in front of the plastic plate that lies on top of the bumper. I am assuming that the seam is the issue--but how to treat it? My issue is right on the joint. Any ideas on how to battle the salty Michigan roads' assault on my beloved Rover?

 

put on some rust converter,
prime it,
paint it ,
then use Silicone paste on it

 

The rust may be too deep and need to be cut out. Take it to a body shop and have them do it and while it is there, have them do a full inspection cause you probably have more going on that you haven't seen yet.

 

X2

You probably have a lot more underneath, which would explain the spot popping back up repeatedly. Rust is like an iceberg, I learned that lesson the hard way