On 27 Mar 2005 18:41:57 -0800, "Mark" wrote:
Investigation revealed the 60 foot sensor wire had a break
in it somewhere. Connections looked OK. No visual sign of damage, but
cutting it in about the middle revealed black crumbs instead of copper
wire. Turns out entire lengths of the wire had corroded to dust.
Probably had worked so long because it was only handling a half volt or
so AC signal. It was non-tinned and had lousy insulation, sort of like
extension cord wire.

So it can happen, at least in small gage wire.

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And larger at times. I once had a similar condition with the shield
braid on a coax cable. Apparently the outer insulation had developed
a pin hole leak allowing moisture to enter. The copper braid in that
section had turned to green powder and was totally non-conductive.

I'd vote for tinned wire if longevity, reliability and low maintenance
are a future concern.