Chain oil residue should help seal out the elements. I wipe off the excess oil with a rag only, and no soaps or cleaners. Aluminum is slightly pourous, so perhaps my lack of more thorough wheel cleaning methods has saved mine from oxidation so far? I don't know.
The good news is, the rear wheels come off very easily. I watched the pit crew at Dinqua's remove one off Steve's ride at around 30 seconds.
(I kept looking around to see where Junior Johnson was hiding.)
