Naca5

Mike, in some cases, under the high load of some mechanical contacts (such as the end pressure of a screw fixing), microscopic galling can occur due to expansion and contraction due to thermal cycling. Typically, this is worst for soft metal against hard metals, moderate for hard metals against hard metals and of least concern for soft metals against soft metals (but results can vary enormously and can sometimes, for some specific combinations, be very different form this general principle).

But yes, this is typically much less of a problem than electrolytic and crevice corrosion.

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I’ve no wish to turn this into a physics lecture, but contact emfs and galvanic corrosion aren’t the same thing. If they were, thermocouples would need an electrolyte to work.

In the unlikely event of anyone being interested, here’s a good explanation of the physics:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/tcoup.html

Mark

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See my answer to Mike above for other reasons why screw contacts may not be as good as they appear, particularly with rhodium as, although inert (a ‘noble’ metal), it’s quite a hard metal.

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I am just trying to keep this on track in practical terms as applied to speaker cable connections.

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