i think Rich Brooks is able to have these coated (paint or Powder).. He has the codes.
I went the same route as Andy. Polished the aluminum(removed the machining) and sealed it. When I first got these from John, I asked what he did to seal the raw aluminum. He stated he use a produce call ZoopSeal. Zoop Seal had become ShineSeal and that is the product I used.
I did the top vents about 8+ years ago, the vents dont see a lot of the elements except for water from a wash. They still look very good.
Easy to clean off and reapply the product. The product does have a shelf life ( 1 year i think) , but I would probably still try it again if needed.
My kit didnt have the polish, just the sealant. Think the results would have been even better with the polish.
This product claims resistance to 700 degrees. I've seen no indication of heat affect from a hot engine, unlike the plastic parts.