If you refinish guns you will eventually run into zinc alloy and/or aluminum parts such as trigger guards and receivers that need to be re-painted. Improper priming or pre-treatment can lead to paint failures. There are specialty primers available for these alloys but I was looking for something reasonably priced yet effective. I have found that Birchwood Casey's Aluminum Black does an outstanding job of creating a paint friendly surface. The phosphate oxide created by the chemical action gives an almost Parkerized surface that is chemically bonded to the metal. The paint readily sticks and stays put. I did a zinc alloy trigger guard today. First I gave it a quick bead blast then immediately coated with the BCAB. The metal turned jet black immediately. I let it work a minute and rinsed with water. Then I dried it and shot two coats of fast dry black enamel on it (Krylon). After a 2 hr dry time I could not scratch the paint off! A very economical and durable finish. Perfect for those Rem 870/1100, Marlin 60, etc. trigger guards. An alternative treatment is to do a flat paint coat followed by a clear enamel clear coat.