I used POR-15 on my rusty gas filler tube. I'm quite happy with the results.

I bought a POR-15 Starter Kit (that's what it's called) for $16 Cdn. It consists
of a 4 oz. bottle of Metal Ready (kind of like a primer for cleaning and etching
the metal surface before painting), a 4 oz. can of POR-15, two brushes and a
pair of rubber gloves. Although even the 4 oz. can was more than I needed it
beats paying $40 for a US quart.

Now, I'm looking for more rusty areas to paint with POR-15.

Thanks to Fred Brittain for the tip!

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