bingo.

oven cleaner in a bucket to strip the anodization, then sand down. I usually do 200/400/600/800/1200/1500 and if I've got some time to kill, I'll keep going to 2400 or 3200. Then finish it with some polish. With most aluminum, it will oxidize (as mentioned above) unless you seal it with something like zoopseal... if unsealed, you'll have to polish it every now and then to keep it looking good.