From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Newsgroups: rec.crafts.metalworking
Subject: Re: Chrome plating plastic?
Date: Sat, 09 Jan 1999 01:47:08 GMT

On Fri, 08 Jan 1999 08:35:34 -0600, Don Stauffer
<stauffer@htc.honeywell.com> wrote:

>Spehro Pefhany wrote:
>>
>> the renowned PLAlbrecht <plalbrecht@aol.com> wrote:
>> > >Scientific American recently had several Amateur Scientist articles on
>> > >amateur vacuum work.  They were getting surprisingly good vacuums with
>> > >low-cost homemade equipment.
>>
>> > A lot of info on home-made vacuum and vapor deposition equipment can be found
>> > in the old Scientific American "Amateur Telescope Making" series of books.
>> > They've recently been reprinted and "improved" by leaving out stuff, I don't
>> > know if the vacuum stuff made the cut or not. Book 3 of my old set has it.
>>
>> You can use sputtering at a much softer vacuum than vacuum evaporation,
>> IIRC. Scientific American had an article on coating telescope mirrors with
>> aluminum by sputtering, but I don't think they used the RF fields used in
>> commercial sputtering equipment. Then again it has been 15+ years since I
>> read the article and I can't remember where I left my glass 3 minutes ago.
>>
>> --
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>> Spehro Pefhany                                    "The Journey is the reward"
>> speff@interlog.com
>> Fax:(905) 271-9838                      (small micro system devt hw/sw + mfg)
>> =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
>
>I asked one of our vacuum techs yesterday about vacuum aluminum
>plating.  He said you DO need a pretty good vacuum, or else the aluminum
>molecules will oxidize before they hit the target.  Also, he said they
>use even more current than someone suggested several days ago.  He said
>once the aluminum is melted, they hit it with 50 amps!  This is to
>complete the process in a hurry to minimize any oxidation from residual
>oxygen atoms.

Many of these systems are set up so the piece to be coated is
protected so it doesn't "see" the aluminum. Once a decent vacuum is
attained sputtering is started and this pretty well cleans out the
residual oxygen in the system.

Now the piece is uncovered and sputtered.