Brett wrote:
>
> I have a 90 Vanagon and it has seam rust at the drivers
side just below the back of the door.  The rust has not
broke through but has bubbled up some.  Should I grind it
out putty and paint? What is the prognosis on stopping it
and having my van live on rust free for year to come?

Hi Brett,

The first thing to learn is that Vanagon seam rust almost
always starts on the inside and works its way outwards.
This means that you cannot kill seam rust from the outside.
You must treat it on the inside if you are to have any hope
of stopping it in its tracks.

I had rust in several seams around my Vanagon and therefore
decided to remove the whole interior.  I spent several days
treating the rust with a phosphoric acid based rust killer
(UK brand "Kurust") and applying a corrosion preventing
liquid wax (UK brand "Waxoyl") which inhibits further
rusting by excluding oxygen.

Several weeks later, after allowing the wax to dry, I
treated the exterior rust by picking out the mastic sealant,
sanding away rust, applying "Kurust" and finally applying
new mastic and paint.

It's worth using a top quality non-shrink mastic that
remains flexible for years.  Cheap mastic tends to shrink
and crack, allowing water (and salt) ingress that starts the
rusting all over again.

I have used this approach on several vehicles over the years
and it seems to stop the progress of all but
well-established heavy corrosion, which obviously needs
panels cut out and replaced.

If you only treat the outside the rust will return within
weeks or months.  Treat the inside and the outside and your
repair should last years.

HTH,

Tony