Re: anodized aluminum for high vacuum?

Am Sun, 26 Oct 2003 12:36:50 GMT, Grant Kiehne postete:

> I've done some preliminary investigation into this method.  A start-up U.S.
>company called Microplasmic (www.microplasmic.com) has a patent on such a
>process (I found it on www.uspto.gov).  

Great patent strategy. That method is much older than the german
reunification. My former collegue worked during his PhD thesis on that
Method and that was at the beginning of the 80'ies (in the former GDR)
;-)

>the trade name CeraFuse from Ceramic Coatings Technologies
>(www.cerafuse.com).  

Good name, ANOF coated aluminum feels and looks like ceramic. Even if
it is not of your special interest, it can be quite colorful i.e. with
small amounts of Co salts used in the electrolyte.

>The process yields a hard, dense alpha-alumina layer
>covered by a gamma-alumina layer that is buffed off.  With buffing only, the
>surface of the alpha-alumina is quite rough (~120 microinch), but it can be
>diamond grit polished like a piece of sapphire down to the desired
>roughness.  I am interested in ~32 microinch or better.  Reportedly, there
>are some pores due to the micrplasmic discharge (sparks).

Yes, there are a few pores and no, they do not make trouble. I've
never experienced a better protective coating for Al than this. 

>Might
>there be non-U.S. vendors who can apply a similar process?  I wonder if the
>Microplasmic process is patent-protected outside the U.S.?

Yes, there is a scientific life even outside the US and sometimes they
hold patents. As far as I heard it is patent protected in Germany by a
company making coatings for Titanium implantates. If you already have
a company on hand to coat your material, I'd really go for this
coating. 

Btw, it is not really difficult to build your own coating machine. All
you need is a receipe for an electrolyte, a single 400-2000V DC
sawtooth generator having some power and a stainless steel or glass
vessel having a steel-ring electrode. If you switch the lab lights
off, the sparking vessel looks really great ;-)

Kind regards,

Ansgar Kursawe

-- 
The two most common things in universe are hydrogen and bureaucracy.