yes, it will oxidize aluminum, but that oxide layer is good... it just looks ugly.
i've used oxiclean for many kegs when i first get them (all used), and it works quite well to clean them up.
Walk-In Serving(14): Oatmeal Stout, Hard Cider, Belgian Tripel, Liquid Stupid, Belgian Dark Strong, Red Bull, Rye IPA, Double IPA, Imperial Stout, Irish Red, Scottish 70/-, Belgian Wit, Nut Brown, Traditional Mead
Walk-In Cold Storage(~50): Cysers, Braggot, Melomels, Ciders, Traditional Meads, Persimmon wines, Dry Stout, barleywine, cream ale, sodas, Chocolate stout, milk stout, and others I can't recall.
Fermenters (0): Nothing current.