There's a real mix-match of what trim pieces are made out of what type of metel. Chrome is virtually non-existant other than bumpers, the header panel trim on my Malibu below the lights is chrome. Most rocker moldings are stainless as well as most wheelwell moldings. There are also aluminum wheelwell moldings. Window trim is all aluminum.
The neverdull polish and others like it will work on raw, non-anodized aluminum. That's why at the demonstrations they use pop can bottoms.
Chances are you'll have to either strip it with the oven cleaner trick, or the best way would be to send it off to a place that will re-do it the correct way by stripping, repairing, polishing, and re-anodizing it.
I have tried striping it and polishing it, but it doesn't hold the shine, and is very sensitive to scratches, even from your fingers.
I've been collecting pieces that are as nice as I can find, and when I paint my car a few years down the road, I'll send them off to be redone the right way.