just started working on project car again . car was in primer when i bought it , surface rust was starting to show through the 1/4 panels so i D a sanded it with 80 grit and it all came rite off down to bare metal . The metal has lots of scratches looks like they striped it with 50 grit . I was able to sand most out with the 80 grit.. What primer self etching or epoxy or just a 2K urethane. I was gona hit the bare metal with 180 and the paint store guy said no just use the urethane , don't sound rite . I did body work in the late 70s to early 90s so all this is new !! to me . Im old school putting filler on top of primer makes me wonder ? I did the fendrs and doors , bodywork over bare metal then urethane hs 2k on top of the filler . so which is better to start with self etching or epoxy ? I got 2 quarts of sem self etching that epoxy is expensive !!! then a good sand able filler primer for all those scratches whats a good affordable one ? thanks

Epoxy all the way. Follow the manufacturers reccomendations about prep.

Etch primer is used in collision shops where speed is a priority. It does okay.

Epoxy primer is used by restoration shops as they are not in a hurry. Epoxy is best.

2k primer filler is used on bare metal by monte carlo driving mullet heads who don't know any better! J/K!

I agree with Darrin,
Epoxy is what I have use the past 34 years with out any problems. My brother worked for PPG for years and the original DP epoxy was fantastic.. then they removed the lead from the epoxy..now it is called PDLF (lead free)..I don't like it and I talked to the Rep about this... he told me on a brake that he couldn't tell me this in the class..but anyway..he told me not to use the DPLF..he told me to use the Omni Epoxy, it was closer to the original epoxy. So I have been using it for years..and I have had no problems.
You have a 3 day window with it to apply body filler, primers or top coat with out sanding.

for bare metal, epoxy is the best thing you can do for adhesion and corrosion resistance. I used a 2k urethane surfacer on top of the epoxy, then paint.

the etch prmer will give a better bond on smoother metal. the epoxy needs a better profile as it requires it to properly adhere . the epoxy is harder but , they make it with a 7 day re-coat window. just be sure that you use a zinc rich style primer [direct to metal] and rust will be controlled with either one..

All very good replies. I agree epoxy is way to go BUTT. Watch how smooth you get it and keep your paper changed out. If you try to save $ by using paper a long time you actually will get to a point that you are not cutting the metal just more or less polishing it. Epoxy is a strange animal. It's more a chemical bonding product but still needs that mechanical bond you get with a sand scratch profile. Really watch your top coat times. Epoxys are a very slow drying product which is the reason why they (in PPG Products) have 3,5 and 7 day top coat windows depending on not only product but catylist too. I would agree on the Omni/Shopline Epoxy being close to the original DP. Naturally it is lead free too. I have been told the shopline epoxys are a 3 day top coat where as the DPLF 401 is a 5 day but the 402 is an 8 hour window. I have been using the DPLV series recently. Not totally a true surfacer product that's direct to metal but not a true epoxy either. Will actually powder up like a surfacer and not gum up like an epoxy if you have to sand it. Say priming something and getting back on it after the 7 day top coat window. It isn't designed to replace a surfacer but can and does do some filling. It may be worth looking into if you are spreading a project out over months or years. It's not a cheap product but if you figure you put epoxy down then month later sand it all or partially off to continue where you left off its cheaper cause you can hand sand it to prep it for surfacer.

The roof on my '69 Coronet 500 had surface rust, and after sanding, and acid cleaning, prep wiping... I used a thin coat of the PPG etching primer? Not even sure it was a primer, maybe an adheasion promoter, it was really thin and almost clear/yellow color (this was 20-years ago.) I then used the Epoxy primer over that.

You will want to use Epoxy primer. I use MetalPrep before I spray the epoxy when I can't sandblast the surface as there are always pits. If this is old metal, sanding will not clean the pits out. Follow instructions carefully as you must clean the surface and neutralize before the epoxy.

Do note that you must paint the epoxy within a week with primer etc, else you will need to scuff the surface when you shoot next.

Astrobuf