I'm not sure how UV stability pertains to raw aluminum, but with a bright dip process, you should see the exact same performance as raw aluminum. Esentially, you are polishing or brightening the metal, which does not really affect its properties. In fact, you may make it worse, from a visual standpoint, because you would be able to see small spots of oxidation easier on a bright, reflective surface.
When most people talk about UV stability, they are talking about paints, powdercoatings, dyes, etc although I have also seen a normal nickel acetate seal for anodize turn yellowing over time when left to exposure. And dyed anodizing can be very hit or miss, depending upon the type of dye used. Colorfastness is key for outdoor use.
-Dustin Gebhardt, CEF
Advanced Manufacturing/Finishing Engineer
Moen
Sanford, NC