Aluminum has a higher reflective index (great for polishing) than any other metal ,as long as it's not cast aluminum. If you want them to look like a mirror start with 80 to 120 grit sandpaper and work your way to 2000 grit in intervals of ~approximately 300 grit. You must remove all the pitting. Then get a buffing wheel with a wool pad and start with red rough compound. when mirror like, spray with polyurethane with a very good UV protector. Or after sanding to 2000 grit , take them to be triple chrome plated. plating shops will do all the work for $$$$$ They can dip in copper to fill pits ,then sand and repeat until smooth. Then into to Nickle tank, then chrome. left out a few washings in acid and clean deionized water in between the metal applications. You can polish aluminum to be more reflective than chrome.