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Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
Since I have not able to do a decent days work lately, I have taken to teaching a small class of TOPS students.
These people had to pass a Basic Electrical Certificate, to pass the course.
Most of these people would not get employed in any Industry, let alone the Electrical one.
Most of them were 25-30 and still had never been employed.
But there was a young girl that had just came out of school and while the others struggled with the wires, she was asking me questions about the conductivity of a given size of copper wire.
But, one question that she did ask me that struck me around the face like a wet fish, was this:
Why are Brass terminals still used with Copper wires, considering the Galvanic reaction between the two?.
Now, before you call me a crack-pot, consider this.
In a flushbox in a wall, there is always a chance of moisture getting into the box.
I'd like to argue this one!. [Linked Image]

Joined: May 2004
Posts: 697
What a wonderful question to come from a student!!!

You're going to make me shake a little rust off my brain on this one, Mike. It's been 25 years since welding school. First, isn't brass a mixture of zinc and copper? I'm assuming it's used where you want copper, but need some additional strength. I think copper screws in the small sizes would be useless. I wasn't aware that there was any reaction between copper and brass. If there is, I'd assume it's less than the reaction of other metals. If I was concerned about it I'd use some anti-oxidant compound.


Joined: Dec 2001
Posts: 2,492
Real switches from Austria used to have copper terminal screws.
Dave, I think you're right about brass.

Joined: Apr 2002
Posts: 2,527
I believe that in general for the subject dissimilar-alloy electrically-conductive components, that two considerations are:

1.) The relaitive electronegativities of copper versus brass {zinc/copper} and bronze {tin/copper} are not far enough apart to cause significant ‘electrochemical cells’ to, over time, foster deterioration of the metallic interface.

2.) Coefficients of expansion of copper versus brass and bronze are close enough to preserve electromechanical integrity of the metallic interface.

Joined: May 2002
Posts: 381
Bjarney, going back to my school physics and chemistry I feel you are right on the nail here with your explanation.

I have just had a very enjoyable evening teaching my 11 year old daughter to solder wires – great fun had by all and great bonding both electrically and metaphysically. Could well be that she’ll be the next one to ask Mike some awkward questions.

Teaching kids has to be one of the most satisfying things a person can do. To see the lights turn on in their eyes has to be the most wonderful experiences one can have.

Joined: Jul 2002
Posts: 8,407
Trumpy Offline OP
One thing I said to myself guys, when I saw this lot was, why bother?. [Linked Image]
Nice to see some sort of thinking within a bunch of egg-heads!
Bring it on Hutch, we could all do with working over the Grey matter.
The questions from younger people, are the most trialling.
Good Lord, I sound like my father!. [Linked Image]

Joined: Apr 2002
Posts: 2,527

"...bonding both electrically and metaphysically." is a wonderful description. The world could use a lot more of that.

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