?? Anodizing is beyond the scope of my basement experiments, and I don't think I'm going to spend hundreds to send it off somewhere... or maybe you were just thinking that the manufacturer should anodize it?

Actually, the order card/form that was shipped with it said something about a black finish, but it was marked off, as though it was available once, but no longer.

The only part that needs blackening is the inside of the chimney, of course. Birchwood Casey Aluminum Black would probably be fine, but it's hard to be certain about fumes and using it indoors. Stove paint works. Some high-heat enamels, like engine enamel or even some exhaust paints don't work, they actually insulate.

I'm sure once it's been used with a dozen fires or so, the inside is going to be naturally pretty black- anything else is just a stopgap.