I'm using DuPont's Aluminum Conversion but it doesn't work as well as some
I've seen. I want a little better etch. Also it is too expensive. Who
has a better source? The old literature speaks of a powder form chromic
acid etch. Anybody know where to find it at a good price? Thanks.

"Chromic acid etch" doesn't quite sound right. IIRC, chromic acid is the
alodine part, and phosphoric acid is the etch done to prepare the metal,
after surface oils are removed with a solvent.

Ed Wischmeyer