Self Eching Primer in spray cans
 

Just my FYI from many years of learning from complete paint jobs and paint repairs.

Self etching primer in spray cans is ok at best for small projects up to wheel size.

Car bodies and convertible top frames and big sheet metal panels need the two part formula from the paint store and sprayed with a gun.
This must always be covered with a 2 part epoxy primer such as DP-90 or the like.
Then you would scuff the DP and apply high build primer.

Anything in a spray can will give you limited results and adhesion problems.

Just my 2 cents.

Idk why you say this I’ve used spray cans of self etching with great results. All self etching means is that it’s bites into the metal , usually a form of acidity

2 part give off isocyanates which no respirator stops so use an air fed.

I also always wipe down anything I’m spraying with vinegar it gives it a great tooth to grab onto it. This does the same as a self etching primer . Epoxy encapsulates and to some extent bonds

1K Spray cans have their place, but Im generally with you.

The asterisk being if you have to sand them. For small projects If I choose to use a rattle primer for convenience I apply the color to it in a wet on wet application.

Ive NEVER encountered 1K rattle can primer that didn't clog the heck out of sandpaper when dry sanded compared to even cheap 2 part automotive primers.

I did recently have adhesion issues with the ceramic engine primer. I cleaned all the bare metal then primed it. Painted it with color (also ceramic rattle can) then used a 2K clear over the top for chemical resistance. Looked great. But I put a little tape down like a month later, and it pulled it all up off the bare metal. Should have used a proper epoxy primer, or an adhesion promotor over the bare metal.

How are you neutralizing the vinegar before the next coat?

Vinegar....LMAO