I'd try 0000 steel wool. I can vouch that it works wonders on aluminum parts as I have been wet sanding with various grades grit with a 0000 steel wool finish on old Kawasaki H2 alum motor parts I'm restoring. Gives good results.
I had what looked like rust on the spokes of my wheel, but it comes off without using an abrasive. I might have done a better job with a mild abrasive, or used less "elbow grease", but I got the brown stains off with a soft cloth, and some Windex. Used the old Michael Jackson "rub-a-dub".
I cleaned a few GN steering wheels up that had this problem.. This is easy and works awesome with hardly any elbo grease. Takes it right off and makes the metal look new. Almost any automotive store sells it. :yup: :6: