Painting over a painted surface...

[SpecialFX]

I painted my grills to match my paint last week, and since then I have decided to go for a green and white color scheme, and want to paint them white now. Can I just Primer-Paint-Clear Coat just like I did to paint the black pastic? Or do I need to do something else to make it look right? I tried to get spare grills from the junk (excuse me, SALVAGE) yard, but there weren't many GAs with a front end.

[ccarr8705]

Primer should work. I couldnt sand my grills without having a hell of a time. So I put on two coats of primer then painted the grill then clear coat.

[matts]

yeah, just rough it up a little, then it's like any other paint job :)

[SpecialFX]

Would a wire brush work? I'm thinking that'd get into the inside of the honeycomb pattern easiest.

[tenspeed]

The easiest thing is to get a product called San Ban. It comes in a spray can and prepares the surface for painting. It works good on dashboards and door panels where the vinyl has that crinkled surface.

I got some at a place where they mix paint for collision shops. I used it when I repainted a Cadillac dashboard.

[SpecialFX]

Originally posted by tenspeed
The easiest thing is to get a product called San Ban. It comes in a spray can and prepares the surface for painting. It works good on dashboards and door panels where the vinyl has that crinkled surface.

I got some at a place where they mix paint for collision shops. I used it when I repainted a Cadillac dashboard.

Will that take the plce of primer or will I still need primer, too?

[JoeyK]

Haha, "Sanban" funny you should mention that. it works, don't get me wrong but the active componet in that stuff is good ole Enamel reducer. Anytime you want to paint plastic wash it down w/ enamel reducer before hand. What it does is soften the plastic to allow the paint to "bite in" to the plastic & hold. Otherwise, most primers, sealers & paints will not hold to plastics. (Some of you might have heard of "adhesion promoters"/ same thing, just reducer softening the substrate.)
Just don't go useing Lacquer thinner, it's way to strong for most plastics & will cause some major problems. enamel reducer is just the right strength to do the trick w/out distorting the plastic.

Anyways, to answer your question/ if you already have a painted surface, just sand it down to give your new layer of paint someting to bite into. Primers are for bare metal & or plastics & fillers, etc.

[SpecialFX]

Sanding isn't especially practical inside the honeycomb pattern of the grills though.

[JoeyK]

NOt much you can do if you want it to hold. It's either sand em or watch the paint flake off after a while.:( I have sanded some very tedious things over the years/ I am an automotive painter. it's just something you have to do if you want your work to last. An adhesion promoter or reducer won't solely do the job on a prepainted part. You can spray a sealer on it before paint & hope that'll do it, some epoxy sealers are great at biteing in & taking hold to almost anything but w/out any sanding it's a gamble.

I'd use a 3M scratch pad. It's not that hard to do.

[JoeyK]

Just read you origional post again. If you didn't sand it before your 1st paint application, it will come off. Go to a jet wash & hit it hard w/ the power washer. You'll see what I mean. it'll flake off here & there. I'd do that & then sand it all smooth, then prime & paint. Prime/ because you'll have bare plastic exposed after the jet wash.

[T3rry]

instead of sanding you could just get a wire pipe cleaner and run that through each of the holes to rough em up a bit