Something often neglected with aluminum is preparation.

Start by cleaning it with a good detergent. Get it CLEAN!

Next, clean the aluminum with a ScotchBrite pad and water, nothing else - no soap, detergent or anything - until you get a "water-break-free surface"

What this means is: when you completely wet it down, the water should coat the surface and not "Break" into droplets. It should just stay as a sheet of water over the entire surface (at least until there is so little water that it HAS to break up)

And whatever you do, don't touch it with your hands after it has been cleaned.