Walt:
I am not an expert body man, but here are some of the things I've heard, seen,
and tried.
1) The usual method used by body shops is to grind the rust out if the material
is thick enough. This is no guarantee as sometimes clean metal is pushed over
some small rust pit and it rusts again. I read in some book that you actually
need to look at every inch of the metal with a jewels loop/magnifying glasses
and check for the little rust pits.
2) Cut out the rusted metal in the thin spots.
3) Sand blast the area if it is only small spots using a spot type sand
blaster. I have heard that sandblasting also isn't 100% as sometimes good metal
is peened over small rust spots jus as using method 1.
4) Using Duro's Extend or similar product, or using a product called POR (Paint
Over Rust). I used Extend and it helps alot. Some places on my old pickup were
done about eight years ago and haven't come back yet.
Someone with more knowledge can probably add or change this proceedure, but here
is what I've done:
1) Clean thoroughly with a wax and silcone remover such as Prepsol.
2) Grind/sand/sandblast depending on the thickness of the material.
3) If you can't grind out all of the rust, clean up what you can.
4) Etch with a metal conditioner. I have used Dupont's Metal Conditioner in the
past but an now using Kwick Prep as it is easier.
5) Apply Extend, POR, etc.
4) Dry sand again with 120 or 180 grit.
5) Etch bare spots again with a metal conditional.
6) Wipe down with a reducer for the primer you're using.
7) Tack off.
8) Fill low spots, etc with body filler, etc.
9) Go back to step 5.
10) Prime using an overall body primer, not a spot primer.
11) Prime using a primer/surfacer or apply a sanding surfacer.
12) Wet sand.
13) Fill slight imperfections with the appropriate filler.
14) If you sand through to bare metal, go back to step 5.
15) Let it thoroughly dry several days.
16) Wipe down with (enamel) reducer for the paint system you're using.
17) Tack off.
18) Spray color and watch it run, fish eye, get dust in it, orange peel, bleed,
lift the under coat edges, etc.
19) Wait a week
20) GO BACK TO STEP TWO.
21) After a year or two start over, just kidding.
Right now I am doing mechanical work on a car that I painted 25 years ago which
included some rust. So far I haven't seen any rust and I didn't use all of the
steps above. Of course the car hasn't been in the rain much, is garaged all the
time, and not driven in the winters.
Blake
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