You might check into black chrome, black nickel, and ebonol. Not sure how conductive they are and if they are appropriate for aluminum, they just came to mind.
Also, check out the excellent site www.finishing.com
I think there may be a few misconceptions in the above thread...so here are a few thoughts. I work with aluminum enclosures in the aviation world and have often been bit by aluminum interfaces. In short, bare aluminum or chemical conversion coated films both stink as conductors!!
1)chemical...
