Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Copper Discoloration

Copper Discoloration

Copper Discoloration

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.


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:

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

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:


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.

RE: Copper Discoloration

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?


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

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close