On Fri, 30 Sep 1994, Roland Dudley wrote:
> > they immediately painted the shell with Ditzler DP40 primer. This is a rust
> > inhibiting primer that seals out moisture.
> >
>
> If you read the instructions for DP40 you will find that a top coat
> should be applied within 7 days. Supposedly DP40 can be scuff sanded
> after this time for good adhesion but this could be a problem in
> hard to get to areas.
>
> Roland
This worried me when I did the interior and bottom of my car. It seemed a
bad idea to let the bare metal sit and rust until I was ready for final
paint, and I worried the finish paint would not stick well if I left the
primer too long (it gets *exceedingly* hard as it ages, and sanding it is
like sanding porcelain). I compromised.
I put a thin coat of DP40 on the bare metal immediately after sandblasting
or sanding to protect the bare metal. This coat was thin enough that the
roughened texture of the metal (from sand blasting) was not fully covered,
and the paint had some surface roughness. When I was almost ready for the
finish paint, I scuffed the primer with a scotchbrite pad anywhere this
was easy to do. I did not mess with scuffing complex areas. Instead,
reasoning that a strong suit of primers like DP40 is their ability to
adhere under adverse conditions, I put another coat of DP40 on, then
followed that within 7 days by the final paint. So far, so good.
On outer surfaces of the body shell, I applied DP40, then any bondo
immediately over the DP40 within 7 days. I did all my bondo work, then
applied DP40 over any bare metal and bondo, followed by primer surfacer of
a contrasting color. I block sanded the primer surfacer, applied stopper
and sanded as necessary, then as a last step applied a coat of thinned
DP40 as a sealer. I let this cure a week or so, and sanded it
thoroughly with 500 paper before the final paint. (Once the DP40 has
cured, it is pretty easy to sand it with 500 paper without going through
to previous layers.)
If there are any pros on the group, I would be interested in the steps
they follow.
Ray Gibbons Dept. of Molecular Physiology & Biophysics
Univ. of Vermont College of Medicine, Burlington, VT
gibbons@northpole.med.uvm.edu (802) 656-8910
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