Re: anodized aluminum for high vacuum?

"Josh Halpern" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]
> Grant Kiehne wrote:
> >Does anyone have experience using anodized aluminum parts in a high
> >vacuum or ultra-high vacuumm (UHV) system?  I am investigating using
> >some relatively large-area anodized aluminum parts in a system that
> >must achieve ~5x10^-8 Torr (cool) after baking at 135 deg. C for ~12
> >hrs.  The alloys are 6061-T4 and 6063-T5.   This yields a
> >fresh native oxide on the aluminum surface.  My application requires a
> >thicker oxide layer (microns).
> >Grant
> >
> Generally one uses stainless steel for high vacuum.  
> Al might be ok for 10-8
> josh halpern
> 
Yo, Josh, old bud,
Easy on the that "generally". I think that all non-load bearing,
non-ablating space vehicle skins are made from Aluminum, 
2024, 6061 or 7075, about the thickness of a beer can.
Most of it is not even anodized, but bare, maybe CrO4/SiF6 treated.
The pressure in space at 130 - 140 miles up is about 10e-6 torr.
250 miles up at MIR we have a vacuum of about 10e-8 torr, and
at the Hubble Space Telescope at about 370 miles up the pressure 
is near 10e-9 torr. Alu appears to serve quite well.
Have fun, Josh,
hanson