Hardy Landskov wrote:
> Thought I would jump in and tell you my tale of woe about using THHN
> insulated wire.
> I bought a 1000 ft roll of #12 copper from Home Depot to make some 160
> meter radials. After about 2 years, the insulation had turned hard and was
> cracking. When I peeled back some of the insulation from one of the wire
> ends, the wire had a greenish sticky substance all over it. I asked N7IR
> who is fairly knowledgable in chemistry and he said the insulation
> outgasses a substance that attacks the copper. Wish I could remember
> exactly what he said it was.
Probably Chlorine (as in Poly Vinyl Chloride?) which forms a nice green
Copper Chloride (aka verdigris)
I've only seen it when there was moisture involved (e.g. wire that had
sat in a flooded conduit AND had cracks in the insulation)
> With that info, I immediately took down all the radials and stripped off
> all the insulation. They were a real mess. The wire cleaned up nicely using
> a soapy type of brillo pad and a garden hose.
> Out here in AZ practically nothing lasts in the heat and ultra violet we
> have. I was happy to catch the problem before it got worse. Of course, YMMV.
I don't know that it would be a significant long term problem. It might
form the surface layer and then stop. I don't think it's like rust,
where it keeps on eating away (after all, there's only a limited amount
of Chlorine there to do the mischief.. unlike rust, where there's the
whole atmosphere to provide oxygen in unlimited quantities)
Don't know for sure, though.
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