Piece of T&E behind a hardboard facing on a damp wall of an oldstone-built ex-barn, socket slightly damp too. Lots of green stuff allover the Copper. Obviously the screw terminations are a bit iffy so thefaceplate gets replaced, but what about the cable? Insulation tests L-Nare fine, N-E is ok, L-E is slightly lower than expected.The green stuff is only on the bare ends of the L & N wires - i.e. onlyas far as the insulation, but tracks about 2ft up the bare earth (I tookout a 4ft section to see).So for the chemists here (I'm sure there must be some) what is happeningto the Copper? What is the green stuff? How does green stuff manage toreduce the insulation test readings? On a similar bit of cable withoutthe reduction in insulation resistance readings would sandpapering thegreen stuff off and re-terminating be ok?This green stuff seems very similar to the usual sort of thing whichhappens to Copper if left outside / in the damp, but its electricalproperties don't really matter on water pipes or roof ornaments :-)Oh, and as to the original cause, stopping the damp is going to bemighty difficult - the wall in question is stone/rubble-built,questionable mortar, and underground :-)Hwyl!M.

All metals when exposed to the atmosphere react and start to corode. Alliminiumreacts almost instantly and over time a white dust appears and this isalliminum hydroxide. copper reacts the same but turns green, cant rememberwether the green stuff is copper oxide ot hydroxide. the insulation test youdid , did you put put 500V through the conductors ? On a digital ohm meter youshould expect a reading of greater than 999 Mohms or infinity on an analouguemeter. yes , emery cloth and clean and re terminate. I work on the 400KV gridOHLines and when we get hot joints ( high resistance , which is what your greenterminations are ) we break the joints , file them shiny clean apply a thinlayer of grease and re make the joints then mega them again.

What happens when Copper gets damp?

Apr 29, 2004 21 Replies

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Wheelbarrowbob 22 years ago

Dont worry, its not the falling off that kills you its the sudden stop at the end ! ( old linesmans joke ) I have just come back from London and looking at the high rise buildings and tower blocks wondering how they fix satellite dishes 5 ,6 ,7 , 8 floors up the side of building intrigues me. i dont think the windows open enough to dangle out so wether the fitters abseil down I dont know. Any one else know ?

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Lurch 22 years ago

On 04 May 2004 18:52:42 GMT, in uk.d-i-y snipped-for-privacy@aol.com (Wheelbarrowbob) strung together this:

The same way the window cleaners get down the side of the building.

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