A good metal polish thats non abrasive but a chemical cleaner is Blue Magic Metal Polish..it does a nice job on oxidation and tarnished metals..I got a few samples from the car show and sent one to Sparkie and kept 2 for my self..I did some polishingon my Son's Motorcycle and it cleaned the aluminum up real nice
here is some info on it....stuff does work..and is paint safe also....
CarGo Blue Magic
and best part its not expensive for a product that works..
AL