Do I need to prime the trim molding before painting?

[peller]

I took off the side molding and the shadowline trim today so I can paint them black, but the side molding seems like it's a plastic of some sort. Do I need to prime this first? I'm painting with Rustoleum Flat Black.
thanks!

[AlarmedBread]

It won't hurt to prime it.

I didn't use any primer, just soap + scotchbrite pad, but I used sem trim black on all my stuff.

[AndrewBird]

Your going to have trouble getting standard Rustoleum to stick to the plastic side molding. You'd be better off getting paint made for plastic and trim, like SEM trim paint, or even Krylon Fusion or something.

Do you have chrome window trim and are painting it black, or do you have factory black trim? If you have the chrome trim (actually, anodized aluminum), they you are going to want to sand it with sand paper first or else the paint won't stick to it either. I would also suggest using an etching primer first, then paint.