One thing I wanna comment on is you may not necessarily remove the oxidized aluminum. Alumina (Al2O3), as it's referred to, is actually one of the hardest natural materials, second only to Diamond. Removing this Alumina actually weakens the piece, and could potentially result in structural weakening.
My team always used to make our aluminum look shmexy with different ways. We simply used a wire brush and brushed patterns into the metal, tedious, but well worth it in my mind.
http://www.team811.com/photo/main.ph...g2_itemId=6739
The benefit of this was the aluminum could still oxidize and have its strength, as well as looking real good!