I stripped down my truck to bare steel and applied self Etching primer and allowed it to dry for about 3 days now. And it's about 70° for drying temp. And I am sanding it at 400 grit. And as It sand it is rolling up. Like eras

er off of a pencil?

 

Etching primer is for a base or foundation for regular primer. It etches into the steel to give the sand-able primer better adhesion. Plus help seal the steel and help protect it. Shouldn't be sanded, not what it's for.

Your going to have to rough it up, sand it. Especially after 3 days to allow the primer to stick. Then apply a regular primer over the top designed for filling, sanding. Assuming your trying to get a nice smooth surface for paint. Don't sand through the etch primer.

 

Well said. There are several types of primers, Etching, which is used to cover bare metal, Epoxy primer which is a 2K based, also to cover bare metal or used as a topping primer before base, and high build, which is the sandable primer used to fill low areas. There is also Sealer primer which is also used as a final prep to base coat.

Wen through a gallon of high build when I did my truck bed after welding new wheel arches in place. Block sanding is the worst, but the results can be well worth the effort.

 

Do some research about primers. I sanded some rust spots to bare metal and applied an etching primer and let it dry for a couple of days before applying a top coat. The rust returned. I learned that I should have applied the top coat within hours of applying the primer.