Surprisingly interesting thread.
I'm building a cooling system for my car which is going to use lots of 6061 and 6063. What treatments offer the best ultimate corrosion protection, most visually appealing corrosion protection, and most economical corrosion protection? The primary areas of corrosion protection were on the exterior of the original aluminum and mild tubing, where the overlapping hoses would trap what I assumed was splashed water during driving. The interior of the original tubing showed zero corrosion after 28 years.