I'm sure there are products out there but I can't make a specific reference.
Maybe Lime-away. W/O reading the label, I don't know if it's OK to use on aluminum. Do check it out. That is, assuming, the problem you have is a small build up of lime. Also, you can ask someone in the Plumbing Dept. in the Home Center for a recommended cleaner. Maybe, at worst, you can try an Auto Supply store and see if there's some sort of cleaning compound and waxing compound for aluminum.