Check the forum for how to prepare an aluminium pot. I think that boiling water in it before using it the first time is advised.
Before I used my immersion chiller for the first time, I put it in my brewpot (SS) in a mild vinegar solution. It cleaned off all of the oxidization and other dirty bits. It'll oxidize after every use, but as long as it's cleaned and emptied after each use, it'll be fine.