For the OP: with aluminum parts, you need to smooth them out progressively. Work out the worst nicks with 600-grit wet sandpaper, then red rubbing compound, then white polishing compound, then finish with Mother's Mag polish. They'll look amazing.

For chrome-plated parts that aren't pitted to the base metal, I use Quick-Glo chrome polish: http://www.quick-glo.com/ . It removes rust and corrosion without any chemicals and very little effort. If the parts are pitted to the point where the plating is flaking off, re-plating is possible, but can be expensive. Replacement is often cheaper.