"John Fields" wrote in message
...
On Tue, 2 Aug 2005 10:40:37 -0500, "DBLEXPOSURE"
wrote:


"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.

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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?

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I doesn't make any difference, (but there is no metal named "coper",
so i'll assume you meant "copper") there won't be any corrosion
unless the dissimilar metals are in contact with each other in the
presence of an electrolyte, not a dielectric as you have stated.

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.

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Less "noble", or more anodic.

If he truly meant a gold-copper couple, the copper, being more
anodic than gold, would corrode.

BTW, pure water _is_ a dielectric and dissimilar metals in contact
with each other and pure water would not corrode.\

--
John Fields
Professional Circuit Designer

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Less "noble", or more anodic.
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Same difference
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not a dielectric as you have stated
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With the preface, "If I recal correctly", Correction noted.

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(but there is no metal named "coper",
so i'll assume you meant "copper")
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BFD