I can't recommend this stuff enough for use on bare cast aluminum. Amongst my car buddies, we like to call it "magic juice" and we use it on everything from aluminum heads, blocks, intakes, timing covers and anything else that needs a good scrubbing. Spray it on and let it sit for a few minutes then scrub with a brass brush or red scotchbrite pad. It is acidic so latex gloves are a plus.
O'Reilly's and Advance Auto carries it in my neck of the woods for about $7 a spray bottle.
Funny thing is I've never tried it on a set of wheels.
Amazon.com: Eagle One Etching Mag Wheel Cleaner...