I too heard the same thing as UKLuge66 from the paint store.
My scenario is that I just got a complete body acid-dipped. I want to seal the metal from further corrosion as the body will be sitting in my backyard under a canopy while I work on the frame and suspension. I am holding off on doing the body work (removing dents, welding in patch panels, etc.) until I finish with the chassis.
I was told by friends that an epoxy primer would be the best for rust prevention while it is outside and not garaged. But the guy at the paint store told me that since I will be doing body work AFTER applying the epoxy primer, I should not go with epoxy because I would have to completely strip it off and reapply it if I wanted to spray real paint on a year or so later. He also said you can't do patch work with epoxy primer (i.e. sand down a dented section to bare metal, repair dent, then respray epoxy on that bare patch). He recommended (and sold me) this Xtreme High-Build Primer/Sealer (http://www.autobodybrands.com/primers/fliers/5425.pdf)
. It claims to be an epoxy hybrid with good sealing qualities. Although, I just found out, after already spraying some fenders and the hood, that you must add urethane reducer for the sealing qualities, which I did not do. As I was spraying, the stuff just seemed too porous, and I really wonder whether it will actually seal against dew and moisture or rather absorb it.
Now I've come across threads that say you can paint over old epoxy primer by just scuffing it up. My question is whether you can do body work with epoxy primer (not bondo work) and apply surface fillers over it to get the body perfect before doing a topcoat.
Any advice? I'm scheduled to get the doors back from the dipper this Saturday and the main body the following week. I'd like to know if I should be switching to something like the SPI epoxy primer or stick with what I've got.