[NewCandle] Anodizable metals and essential conditions forglowdischarge?

[Keith Nagel]

Hi Horace,

You write:
>It still seems to me possible a significant glow occurs within the  
>electrolyte near the surface.

If that is true then in the porous film the glow region
would tend to extend thoughout the entire pore, rather
than being concentrated at the surface of the inner barrier layer. 

I expect that the glow phenomena matches that seen in ordinary glow
discharges on electrodes in air/vacuum. That is to say, there is
ignition and a glow discharge, then an anomalous glow discharge
after the entire active surface area is glowing and more voltage
is applied, then finally a breakdown to a spark. The pores would
affect the anomalous glow region, and the eventual spark
breakthough would be channeled by the pores.

A crude graph of the discharge regime can be found here.

http://www.mksinst.com/docs/R/eni-SYE-TN.aspx

( as an aside, I suggested this power supply combo to Ed Storms for his
recent work on glow discharge. It's just the thing for working the AGD
region ).
 
you also wrote:	
>I had no luck with magnesium when I tried it.  It may well work with  
>the right electrolyte.  I would guess acetic acid would have the best  
>chance of working.

There are commercial processes for anodizing magnesium, so there is 
place to start. This page has a roundup of some of them.

http://www.finishing.com/faqs/magnesium.html

I wasn't sure from a quick search whether the resulting anodized layer
could be pure magnesium oxide or just a chromate or phosphate.

K.