There are two ways of removing aluminum corrosion that I've used:
1. For really serious corrosion/pitting, get an aluminum etching cleaner. the name says it all. The cleaner will chemically combine with the corrosion, loosen it and allow you to wash it off the wheel. It usually produces a foam that cleans off easily. The downside is that you will actually be removing aluminum from the surface of the wheel. Also, you'll need to polish the rim when done.
2. The best way to remove the corrosion is to use an alloy mag wheel polish, a high grade polish like Mothers. Leave the Mothers polish on the rim for 10-15 minutes, then get a hand drill and a mag wheel polishing/buffing wheel. The buffing wheel will clean the rims nicely, and also your wire spokes, and nipples. Buffing does remove a bit of aluminum from the surface, but less than an etching cleaner. Letting the drill do the work, you won't have carpel tunnel syndrome afterwards. Another plus to this method, you get to use a power tool.
If you polish the wheel periodically, each polishing session will be quick and easy.