In article ,
Stealth Pilot wrote:

On Fri, 2 Jan 2004 07:38:53 -0500, "Larry Smith"
wrote:

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.

the standard alodine etch is a dilute phosphoric acid.
dont know what else is in the mix to moderate its action though.
Stealth Pilot

You can set up an alodine tank and an etch tank. The steps a

1. Thoroughly degrease the aluminum (acetone, MEK, lacquer thinner)

2. Dip etch in a room temperature lye solution for about 3-4 minutes.
You can buy Lewis Lye at a supermarket.

3. Rinse the aluminum.

4. Dip the aluminum in a warm (120 deg F) alodine solution about 10
minutes, or until it gets a light gold color. You do NOT want it to turn
brown! Just a very light gold color is all you need.

5. Rinse the metal.

You MAY be able to get alodine powder from a plating shop -- that's
where I got some a number of years ago.

Always wear rubber (or vinyl) gloves when working with this system.