There seems to be a lot of confusion on just what anodized aluminum is (a layer of aluminum oxide).
"Anodizing will protect the aluminum parts by making the surface much harder than natural aluminum, aluminum oxide is grown out of the surface during anodizing and is extreemly hard. The porous nature of the anodized layer allows it to be dyed any color that is required."
From an artical on D.I.Y. anodizing and reanodizing. Read more at: http://www.focuser.com/atm/anodize/anodize.html