I have never seen it, but have heard about it during investigation of 'Green
Plague'.  The electronics industry term is "Red Plague" not Plaque, and is
corrosion associated with the use of silver-plated copper wire.  Red Plague,
named for it's color, (as opposed to Green Plague) is the cuprous oxide
(possibly with some black cupric oxide)corrosion product that forms when a
galvanic cell is formed between copper and silver.  This was first studied
in the sixties when it was established that 'red plague' originates at
breaks in the silver plating of copper wire strands in the presence of
moisture and oxygen.  Although 'red plague' corrosion of silver plated wire
in service is extremely rare, for high-rel space applications, it is
necessary to control all steps in the handling and processing of the wire.
Control seems to be mainly by the wire manufacturer to provide a quality,
uniform plated thickness (at least 2 um and preferably 4 um) of silver
without imperfections such as scrapes or porosity.  It is important that
manufacturers ensure they do not damage the continuity of the silver
plating.  In addition, humidity controls can be implemented (dry-nitrogen
backfill or desiccant) for dry packaging to keep wire reels or spools below
50% RH.

More information is available and can be found in this book:
Metallurgical Assessment of Spacecraft Parts, Materials and Processes
(Second Edition)
Barrie D. Dunn
Praxis Publishing Ltd.
(See http://www.praxis-publishing.co.uk/space/metal.htm)

> Rainer G. Blomberg
> Honeywell -Space Systems Clearwater
Staff Production Engineer
> 13350 US Hwy 19 N MS 802-3
> Clearwater, FL 33764-7290
(727) 539-5534 Phone
(727) 790-8738 Pager
(727) 539-4469 Fax
e-mail: [log in to unmask]



-----Original Message-----
From: Kasprzak, Bill (sys) USX [mailto:[log in to unmask]]
Sent: Friday, November 30, 2001 3:08 PM
To: [log in to unmask]
Subject: [TN] Red plaque on Silver plated wire?


Anybody out there ever hear about having to control red plaque on silver
plated wire?

This showed up on a spec for a job we're contemplating.

Any and all ('cept wisecracks) responses appreciated. Thanks.

Bill Kasprzak
Moog Inc., Electronic Assembly Engineering

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