The Stovebolt Site Forums The Shop Area Paint and Body Shop epoxy primer over 2k urethane primer?

Im having some issues with my priming process on my cab, doors and front end sheet metal parts. My cab was blasted with walnut shells and the fenders with copper slag. Etching primer was then sprayed over the bare metal, filler work was done after scuffing the etch primer, then re-etch primed over filler and spots that were sanded to bare metal from sanding the filler. I then sprayed 3 coats of 2k high build urethane primer but it did not fill the scratches and pits left from the copper slag. My body man told me it would fill them but i should have sanded the parts first so they were smooth before priming. wondering if i should wet sand or scuff the urethane primer with 400 then spray epoxy primer over to fill the scratches and pits? maybe this is a no-no. looking for some opinions of what my best option would be. Might just have to sand everything off and start over?

I'd dry block sand with 180 and re-prime. Regardless of how shallow a scratch is primer is not going to settle into it and level itself.

Isn't that the idea behind high build primer?
You spray it on to fill the scratches,etc. and then you sand it between coats to level it out?
Thats how I thought it was supposed to work ?

yes, that is how it is supposed to work. This is my first complete paint job from bare steel, so I was following what the tech sheet said and it said to wet sand the 2k with 400 grit prior to sealing or 600 prior to top coat. I was hoping not to have to re-apply the 2k primer but with my deep pits i have to. Thanks czechman for the info, i sanded with 180 dry today and it leveled things up nicely. I'll spray more tomorrow then wet sand with 400 or maybe 600 if there are still scratches.

I have been an automotive painter for well over 15 years. Alex63, you did every thing correct as far as using etching primer over steel, then performing the filler work and re etching. The main thing to keep in mind is the 2K is a high build, it is not sprayable bondo. If there are pits or deep scratches, you will need to either apply filler or prime, block and reprime. The 2K primers are so much better than the lacquer primers we had before but there are still some limitations. I know of guys that would use 2K over 40 or 60 grit scratches, for me I would not 2K over anything more than 80 grit.