On Tue, 2 Aug 2005 18:59:37 +0200, "Alexander"
wrote:

Op [GMT+1=CET], hakte DBLEXPOSURE op ons in met:

"John Fields" wrote in message
...
On Tue, 2 Aug 2005 06:42:29 +0200, "Alexander"
wrote:


If you connect Au to Cu and put a Current through it, for best
results AC, the Cu starts corroding at the transistion from Cu to
Au. This is always the
case when putting to metals together, the greater the difference
between the
metals the faster the corroding will be.

---
That's not true.

--
John Fields
Professional Circuit Designer

Firstly, Aluminium is Al not Au. Au is gold. You are speaking of
aluminium and coper?

Galvanic Corrosion Is possible when Al and Cu are in contact with one
and other. If I recal correctly a dialectric such as water needs to
be present. Cathodic protection, (electric current) can be used to
slow or stop this proccess. I Imagine reversing the polarity may
speed it up. Aluminium is the "Less Nobel" of the two metals so I
would imagine that it would be the one to corrode.

Correct I also added the remark of the diëlectricum to the discussion.

---
No you added the remark about the _electrolyte_, which was correct.
---

And your remark about Aluminium is correct, however as stated in some
applications I have seen an Copper core and an Gold (aurum) shell. And since
the combination gold-copper is worse then the well known combination
aluminium-copper.

---
In what way is it worse?

Looking at:

http://www.ocean.udel.edu/seagrant/p...corrosion.html

It seems that the distance between gold and copper (0.52V) is the
same as the distance between copper and aluminum, so why would the
rate of corrosion be worse for a gold-copper couple than for
copper-aluminum?
---

But at least ThanX for confirming my statement and not saying its not true
without giving a reason as someone else did.

---
Whether I gave a reason or not is unimportant, what matters is that
a factual error got corrected.


--
John Fields
Professional Circuit Designer