I've been noticing increasing rust on the gas filler tube metal collar (?)
whenever I remove the gas cap to fuel up my '87 Westfalia. Upon closer
inspection, I found that the flange portion of the gas filler tube wasn't tight
flush against the round, black plastic trim cup allowing water and road crud
from under the wheel well to enter the area around the gas cap. Today, I removed
the gas cap and the black, plastic trim, exposing the end portion of the gas
filler tube. I sanded away the rust until shiny metal appeared. There is
moderate pitting on the surface of the metal but at least its rust free. Now,
I'm at a loss as to how to treat the metal to impede/prevent rust from
reappearing. I suppose I could paint the metal portion of the gas filler tube
with primer or leave it bare and simply saturate the metal with a rust inhibitor
such as Rust Check.

Anyone have a suggestion or had this problem as well?

Roy O.
'87 Westfalia
('till death us do part)