Hey guys, so I primed my car about a month ago, using Dupont 2K urethane primer. I've been reading some paint threads and it seems like some use a sealer before paint, is this necessary? Do I need to sand the current primer before sealer? Also, im deciding between using a single stage acrylic or going 2-stage, for durability and cost-effectiveness, so any advice would be greatly appreciated. Thanks

Good shops use a sealer to hopefully give another layer to prevent any thing from showing up under the primer later and to give a even surface of the same color to make the top coat color to be even overall. Yes the primer must be scuffed so the next coat will adhear. Only with nonsanding primers and only usually within about 12-24 hours will you not need to scuff the existing primer. You can go online and get the tech sheets for any good brand paint.

done this a couple of times--haven't used a sealer on primer.
sand the primer with 400 wet-dry before paint. I've painted the base coat clear coat (malaga red) and it cost quite a bit more than the acyrlic. the metallic alaska blue was about a gallon at $160. the base coat clear coat was about $500+.
I guess from my experience-dangerous amateur- a couple of gallons of acylic to get good coverage and lasting would do it.
and the clear coat is quite potent unless you have good ventilation to clear the area quick---

The sealer goes on and then the paint comes right after. Don't apply the sealer one day and then paint another

NEED ? NO

Recommended ? YES

Charlie hit it on the head. If you have additional body work to do then hell yes, apply a sealer coat on top of it.

Primer offers little rust protection. Sealer and top coats do.

Sealers do a couple things. First the solvents in them are usually hot enough to etch into the harder primers creating an adhesion promotion layer. They usually skin over fast and create a barrier to prevent bleeding of the products they are covering. Some fillers and primers will sponge in your color coat and bleed through slightly causing the top coat to change in spots. And sealers often provide a soft enough skin for the top coat to bite into without sanding. ( caution, they have a window for this) Early on in the development of base coat finishes there was a problem with adhesion. HTLA steel in the new cars required a 36 grit scratch to allow adhesion. Hence the development of acid based primers, as a self etching first surface and two part surfacers to allow for hard but flexible chemical bond.

Some of this may be B.S. I was making it up as I typed.. or was I.....

I call BS....get back to work.

Rich

I needed a mental break. This place is such a distraction...

All the above and not much bs. Sometimes a top coat because it has hot thinners or reducers will penetrate to the fillers either bondo or the primers and soften them and the outline or scratch line of the filler might lift or later shrink and show through to the top. Sometimes you can buff it out and sometimes it will look smooth and about a month later it will show up again. This can go on for a couple of years or until you cut through the top coat and get to put more on and try somemore. Sealer coats are cheap insurance. The sealer is a barrier between the filler and the top coat, to prevent all the screwing around and wasted top coat costs and additional labor. This is similiar to putting gel coat over a fg repair to stop the print through from the strands about a year later after the shrinkage.

The top coat choice will determine what sealer you will want to use. It's really better to have all the paint stuff planned before the filler ever goes on. Try to stay with the same paint mfg.

It's all about money and time I guess.