Hmm aluminum etching is a no brainer.   What the heck is a conversion
   coating?  I thought it might be a neutralizer.  Sounds like I am wrong.
   Perhaps a chemical reaction with the aluminum to create a coating onto
   which the epoxy could stick to? ?

Dupont 226S conversion coating it is an alodine. $50.00 a gallon goes on
after the $50.00 a gallon acid etching and must go on emmidiately. I
have it in gallons if you cannot find it in Japan. You will only need a
very small amount. I can put some in a small container for you.

Dan