Aluminum won't rust, and the paint will add unnecessary weight. Entering a beauty contest are you? <img src="/forums/images/graemlins/smile.gif" alt="" />
Actually aluminum DOES rust, it just takes 20 years. We had some collapsible aluminum tent poles which, after about 20 years, got bubbly white spots on them and the surface got more rough. We actually had to sand them down once to make them work as the aluminum oxide got in the way of the poles sliding.
It won't rust through but it does get surface oxides on it.