Find an HVAC supply store and buy aluminum coil cleaner or A/C coil cleaner. It is pink, it will eat the skin off your hands - so wear good rubber gloves and a pair of chemical goggles. Follow the directions and you will have shiny aluminum - just like the day it came from the foundry. if you dont follow the directions you will have black aluminum.

hose it on, wait a short period of time (I think it is either 30 seconds or 1 minute (on the directions), and rinse with plenty of water. Then coat with something - paint, clearcoat, etc.

Also, if you just want to paint, PPG has an aluminum cleaner that is used when they repaint tractor trailers. Contact your local PPG / Ditzler paint supplier.

Scott

The problems we face today can not be addressed at the same level of intelligence we were at when we created them - Albert Einstein Or with the same level of $ - Me