Do I need a sealer?, Some paint help please Options

[jonferns]

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

[rick 918-S]

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.. (IMG:style_emoticons/default/biggrin.gif) or was I..... (IMG:style_emoticons/default/idea.gif)

[r_towle]

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.. (IMG:style_emoticons/default/biggrin.gif) or was I..... (IMG:style_emoticons/default/idea.gif)

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

Rich