Posted by Sherman in Idaho [24.32.202.166] on Tuesday, April 09, 2013 at 21:43:37 :
In Reply to: Anodizing..... anyone have.. posted by Gary D [50.40.207.124] on Tuesday, April 09, 2013 at 21:08:41 :
If you end up doing it yourself, I'd be curious to know what you came up with. I've played around with electrochemistry since I was a boy (won the science fair by electroplating a bunch of stuff in 7th grade or so), but have not tried anodizing. As a rule, all electrochemical process have a little bit of science and a lot of magic in them. The basic chemistry sounds incredibly simple -- use the aluminum as the anode in an electrolytic cell so the oxygen evolved at the anode reacts with the aluminum and makes a hard oxide (sapphire) coating.
The trick with electrochemistry is that the solution is not just one chemical but it's a "secret sauce" with various additives to give the coating good adhesion, even coverage, the right color, and so on. Preparation is also key, just as with painting. There's also lots of magic in getting the current density (amps per square inch) and the temperature right. What I learned was it's very easy to plate metals out of solution onto other metals, but very hard to make them smooth and have them stick well. I suspect anodizing is similar.
If you just need a corrosion-resistant coating and you don't care what it looks like, and you're not afraid of hexavalent chromium, you might look into a chromate dip with no electricity needed. I used to know a guy who did that as a small shop for other manufacturers and it was really easy and worked well. It gives a slightly golden color that tends to be streaky where the solution runs off of the metal. Of course it could also give you skin cancer and turn your shop into a superfund site.