Roy,
For really neat coatings for aluminum do a search on " home anodizing of aluminum " . The info is astounding and the process simple and cheap . I don't know if you saw the latest wild child offering on 6mmbr , a really cool space gun that has some anodized aluminum parts and the inventor of this rig ( it has a magnetic tuner no less ) anodized the parts himself .
The best search provided article I read was by a Brit and he was thorough . If you do it let me know . I'm still playing with aluminum myself .
Jim B