I bought powder coat from eastwood before. It was for my one of my HS metal shop projects, but I gave what was left to the metal shop because I don't have a powder coater myself.
I've used the Dupont(?) "aluminium" 1200 degree paint on my exhaust. I go over the welds every 3-4 months. It at least slowed the rust.
I'll have to try the black on the drums when I order them.
