1) There was the
standard black rubberized undercoating that comes
off easily with automotive paint stripper, and
under this was a white / yellow undercoating that was very tough,
yet pliable and required considerable effort to remove with a
flat-tip screwdriver using a scraping motion.
2) After the
undercoating was removed, I scraped, dug, and pried as much loose
rust as possible off. I then used a stiff wire brush to remove any
loose rust I had missed. I did this to both the inside and outside
of the holes. When I was done, it looked like this:
3) I then used Mar-Hyde
One-Step (just like EXTEND),
a water-based rust stabilizer/sealer, to prevent any
residual rust from causing future problems. I used 4 thin coats,
about 3 minutes between coats (as it recommends) and then allowed
it to dry overnight. It looked like this:
4) To patch the
holes, I placed aluminum foil on the other side (inside car) of
the wheel well to prevent too much filler going inside. I then
used Bond-O polyester filler to fill in
the holes. There was a lot to patch, so it took 4 batches of
filler to finish. It was quite hot outside, and the filler was
hardening unusually fast. After patching it looked like this:
5) At this point
you should paint the area with a good enamel paint (NOT a
water-based paint.) A can of Dupli-Color
automotive paint could be used, or even a standard enamel like Rustoleum.
Once again, use 2 - 3 coats. This will seal the rust inhibitor and
bondo from water IN CASE water gets by the next step...
6) The final steps
are to apply Paintable Rubber Undercoat (not yer
standard "rubberized" undercoat). I STRONGLY suggest
using Blue Magic rubber coating; it's a marine
/ automotive wheel well / house gutter flexible paintable
sealant that, though ~$8 / bottle, is vastly superior to other
standard paintable rubber undercoatings I've seen. I mean, it
really SEALS and feels like a coat of solid rubber. Spray it over
the entire area and give it a ~3 - 4 coats. In order to camouflage
the repair area, give it 2 coats of your standard Rubberized
Automotive Undercoat.