I wouldn't suggest painting anything on the area you just got done
scuffing with 180.
Reason?
You have just covered up the "tooth" you just gave the metal to bind to
the Seam sealer.
As I stated in my prior message, the sealer displaces water and if you
take the time to spray some bed liner material, or tar or anything
behind the seam it should remain rust free for a long time.
Also, this process is recommended prior to painting the whole van, or
you could, very easily just paint the seam with lacquer, or acrylic
enamel, or paint of your choice.
Just be sure to scuff up the surface prior to applying any paint, so it
will stay put.

Later,

Terry