How to scuff up epoxy primer in order to spray the top coat?

[sireland67]

Wet

 

[Furious65]

Dry sand only but that's just my opinion!

 

[mgoblue9798]

I painted the underside of one of my Mopars with Nason Ful-Poxy 491-12 epoxy primer and then, dangit, life intervened and I didn't top coat it in a timely fashion (48 hours)! To make matters worse, the surface of the underside of the body is very irregular, with many flutes and louvers pressed into the body panels, so it will be relatively difficult to sand. The technical data sheet for Ful-Poxy says to sand it with 400 grit and then 600 grit before top coating it at this stage of cure. I have some questions for you body men: how about using Scotchbrite pads instead? Wouldn't that be easier than using sandpaper? What grade of Scotchbrite? Any suggestions about how to sand a highly-irregular surface like this the easiest way? Thanks very much.

I have not used the Nason epoxy primer, but most brands recommend scuffing and shooting with another coat of expoxy primer if you don't get it topcoated within 48-72 hrs, then applying top coat over that to avoid top coat not adhering properly.

I would scuff it with red scotch brite pads, blow off and clean, and spray another epoxy coat then top coat. I cant see sanding a floor pan with 400 and 600 it would take forever.

 

[ir3333]

OK..the underside is painted with epoxy primer.Perfect, it will be protected forever.
If it is a shade of grey just paint the car and let the overspray hit the underside where it will and you
will have a perfect factory finish....but then again maybe you won't like that?

 

[HowelGrace]

has anyone tried using a grey scuff pad instead of red for a smoother finish before topcoat? I’ve been seeing mixed advice on whether red can be too aggressive, especially on smaller panels or tight spots. Curious what’s worked best for you before laying on color or clear.

 

[HowelGrace]

has anyone tried using a grey scuff pad instead of red for a smoother finish before topcoat? I’ve been seeing mixed advice on whether red can be too aggressive, especially on smaller panels or tight spots. Curious what’s worked best for you before laying on color or clear.

I remember used a red Scuff Stuff pad wet and gave it a good once-over, followed by a clean rinse and tack cloth. The topcoat laid down smooth with no issues.

Reminded me a bit of how I prep metal for applying concrete oxide colours, same idea where you're just giving it enough tooth for the next layer to stick without cutting through the base.