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 diλlectricum to the discussion.
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
But at least ThanX for confirming my statement and not saying its not true
without giving a reason as someone else did.
Look up Galvanic reaction in ship hulls, and you will find that all
Navy ships have provisions to reduce it.
Note again that my reference is to the effect, not the remarks about
specific elements. Learn to read.
But that wasn't the question. You were responding to a comment made
in the specific context of gold-on-copper, to the effect that "galvanic
reaction" was the reason that such a combination wasn't a good idea.
Sorry, but the "galvanic reaction" of dissimilar metals has absolutely
nothing to do with the subject at hand.
There actually very often IS another layer (commonly, nickel) placed
between a copper conductor and a top protective layer of gold, but
this has nothing whatsoever to do with a "galvanic reaction" between
these two metals. (If it did, following the original incorrect response
on this subject, the problem would then become WORSE due to the
fact that there would now be two such interfaces rather than one.
Remember, if you can, that the original comment along these lines said
that a "galvanic reaction" was a problem between ANY two metals.)
The reason that an intermediate layer of nickel is often used in this
case has to do with the fact that, left to themselves, gold and copper
will tend to diffuse into one another. This causes a problem in
electrical applications (where gold-plating copper conductors is being
done to prevent corrosion) primarily on the gold side of things, as
the copper diffusing up through the gold layer will eventually reach
the surface and create the very same corrosion problem that the gold
was supposed to be preventing. Nickel doesn't diffuse into gold
like copper does, hence its use here.
My, again with the personal attacks; I suppose in the absence of
practical knowledge, that's about all one is left with.
The Navy knows it's a problem, but then naval ships are in seawater. One
must have an electrolyte to complete the 'circuit'. This is one reason why
commercial work with Al conductors often requires the application of special
'grease' to seal the connection from moisture intrusion.
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