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Copper Discoloration
3

Copper Discoloration

Copper Discoloration

(OP)
When copper conductors or wire overheat slowly due to slightly excessive current flow, the color of the copper first takes on a deeper reddish color.  If the overheating is continuous that color tends to stabilize and remain constant.  If the circuit is disconnected and allowed to remain unused for a period of time, the copper takes on the usual green color for copper oxide.

What causes that reddish color?
Is that a different oxide?
Any other potentially useful information would be appreciated.

Thank You.

PUMPDESIGNER

RE: Copper Discoloration

Yes, it is a different oxide. Much like heat tinting steel the oxide layer changes color as it thickens. The green is copper carbonate..

look here:
http://www.corrosion-doctors.org/Artifacts/Patina.htm

(just so you know I searched: {Color of copper oxide} on google to find that website.)

Nick
I love materials science!

RE: Copper Discoloration

If I am reading this Wikipedia stuff right, the green stuff is copper (II) carbonate and the red stuff is copper (I) oxide.

See the bottom of this page and referenced pages:

http://www.answers.com/topic/copper-3

Mike Halloran
Pembroke Pines, FL, USA

RE: Copper Discoloration

Ha, Ha, Mike.. I hit enter before you!

RE: Copper Discoloration

Some days just go that way.  

Mike Halloran
Pembroke Pines, FL, USA

RE: Copper Discoloration

As the oxide sits in air it absorbs moisture, reacts, and hence the color change.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm

RE: Copper Discoloration

(OP)
Thank you guys.
Sorry it took so long to get back to you, I was at a conference and then got sick.
Hello Mike, I spoke with you once on the telephone, forgot about what though.  Tarry Baker had me speak at some inspectors thingy about 10-12 years ago, perhaps it was then.
I am analyzing electrical transient failures.  Normally transient failures (usually from lightning), are easily discernable from long term overheating problems.   But at this moment I am working on discerning Short Circuit/Ground Fault from lightning.

You guys have any information on that topic?

PUMPDESIGNER

RE: Copper Discoloration

Ten years ago I was working on blood cell counters and plastic micro- manifolds by day, and hanging out in Compuserve's LEAP forum at night.  I didn't get out much; I'm the kind of guy you keep in the room _behind_ the back room.  Which is sort of where I was; in a mezzanine office in a dark corner of an underused factory, right next to a CNC punch press.

Might have been a different MH; there are at least ten on AOL.

Mike Halloran
Pembroke Pines, FL, USA

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