Subject: Re: Looking for info on Ti anodizing

From: [email-masked] (Paul Amaranth)
Date: 13 Feb 1995 20:07:20 GMT

In article <[email-masked]> THREATCON WHITE <[email-masked]> writes:
>As the subject says, I am looking for hints, comments, reference
>sources, e.t.c.  I am an absolute novice, and as such you might have
>to "keep it simple".  What I seek most, is a set-up that I can 
>create in my home to experiment with this process.  If someone knows
>how to make a "backyard" Ti anodizing lab out of a model train
>transformer, a six-pack of Coke, and a lenth of wire ;-), please
>drop me a line.
>

I did a little bit of this some time ago to make a couple of pieces
of jewelry, let me see if I can recall any of the details.

The colors on anodized Ti or Niobium are the result of an interference
filter formed by the clear oxide layer.  The particular color you get
depends on the thickness of the layer. 

You can anodize this stuff by putting it in a dilute sulfuric acid
solution (very dilute, a couple percent will work fine), hooking it
up to a regulated power supply and then turning it on.  The thickness
of the oxide layer is dependant on the voltage, therefore the color
you get depends on the voltage as well.  I had a list of color vs
voltages somewhere, but the range I recall is 30-80V.  The color
spectrum repeats two or three times in that range.  As you would
expect, surface prep is pretty critical to the final appearance.  For
obvious reasons, you can't buff the thing once it's anodized.

I borrowed the use of an electrophoresis power supply from a biologist
friend, but any power supply covering that range will do.  Current needs
are pretty modest, a few tens of ma will work fine.

It's possible that there might be enough phosphoric acid in Coke to
serve as an eletrolyte, but I never tried it :-)

-- 
Paul Amaranth  Manager User Services - office: (810) 370 4541 (also voicemail)
               (e-mail)     [email-masked]    [Rochester, Michigan  USA]
   Mosaic page: http://www.acs.oakland.edu/links/amaranth/amaranth.html