From: REMOVE_THISdwilkins@means.net (Don Wilkins)
Subject: Re: Coloured metals.
Date: Wed, 21 Apr 1999 12:36:43 GMT
On 20 Apr 1999 21:45:44 -0400, <firstname.lastname@example.org> wrote:
>DoN. Nichols <email@example.com> wrote:
>: In article <371A58F5.2E8C934D@bcstec.ca.boeing.com>,
>: G. Louis Roberts <firstname.lastname@example.org> wrote:
>:>gold and (believe it or not) _aluminum_ yield a bright purple alloy,
>: Yes -- infamous as the "Purple Plague" in semiconductor
>: manufacturing. They used to use ultrasonically welded gold wire on
>: aluminum metalization. The result was eventually the purple color and
>: failing ICs. :-)
>Now, the only question is, is the colour due to an oxide film, or is
>One way to find out I gues..
Roberts-Austen's purple gold. 79%Au-21%Al. Melting point ~750 C.
We used to make purple pennies by forming a Sb-Cu inter metallic
compound on the surface.
The original question was colored (spelling corrected ;-)) metals so
these might be considered cheating.