Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!decwrl!ucbvax!hplabs!hp-pcd!hplsla!tomb
From: tomb@hplsla.HP.COM (Tom Bruhns)
Newsgroups: sci.electronics
Subject: Re: Do you know me?  Remember when I asked about electroplating?
Message-ID: <5170061@hplsla.HP.COM>
Date: 29 Nov 89 20:36:15 GMT
References: <1989Nov28.025554.25199@ddsw1.MCS.COM>
Organization: HP Lake Stevens, WA
Lines: 28

benfeen@ddsw1.MCS.COM (Ben Feen) writes:
>Ok, I've gotten into a good electronics lab, with a lot of equipment.  
>The question is:
>How do I anodize metal?  Aluminum, bronze, etc?  What voltages correspond to
>what colors?
>Please post, I would like to hear other people comment on proposed
>techniques.

Anodize bronze?  Hahaha.  Only plan to anodize metals that form a good,
solid oxide layer.  Basic chemistry teaches that "oxidation occurs at
the anode".  Anodization simply builds an oxide layer.  Titanium and
aluminum are probably the two most commonly anodized (for the purpose
of forming a protective or decorative coating) metals.

The color you see in commercially anodized aluminum is put in after
the anodizing, before the sealing, when the anodize coating is "porous".
Proprietary dies are used, though I have heard of people trying food
colors, etc.

I did a little anodizing at one point, with poor results.  I used a
sulphuric acid bath.  The other common bath is chromate-based (chromic
acid?  I don't recall for sure).  I think almost all commercial
anodizers use the chromate baths.  From experience, I can tell you
that not all anodizing companies can do a good job on all alloys;
some alloys are rather hard to get a good finish on.

Libraries often have books on metal finishing and/or electroplating.
Look there for more info.


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