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PVC Wire Insulation

  1. Aug 30, 2013 #1

    jim hardy

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    Over about the last decade I have encountered with increasing frequency a black corrosion on the strands of copper wire.
    When you strip the wire it'll be jet black instead of old copper brown.
    It cannot be soldered.
    It is a real nuisance when trying to repair something like an automobile headlamp socket or an extension cord that needs a new end.

    It used to be somewhat unusual, then it seemed to be most frequent on particular colored wires, nowadays it's prevalent.

    Three questions:

    1. Might this coating be copper sulfate ?

    2. Might it be caused by sulfur bearing organotin stabilizers in the PVC insulation, as metal based ones are phased out?? (##&I@#!@&^ that 9** partiple EPA )

    3. What will dissolve it and leave me with shiny copper that I can solder?
    I've tried MEK, alcohol, acetone, paint stripper, salt & vinegar to no avail. Scraping gets only one face of outside strands leaving me a joint that I don't trust for high current.

    This is aggravating handymen worldwide, just try a search.
    Sure would appreciate some education here as well as practical advice .

    This is a business opportunity - bottle a cure .
    It's about the only product i'd order from those annoying TV ads.

    Thanks for any help at any level .

    old jim himself
  2. jcsd
  3. Aug 30, 2013 #2


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    I would guess copper(II) sulfide (not sulfate, which is blue) or copper(II) oxide.

    If it is sulfide, try cleaning with ammonia solution. Otherwise, I think this is going to a tough one to remove chemically. The oxide dissolves in potassium cyanide :eek: - but anything that reacts chemically with the oxide or sulfide will probably react with metallic copper as well.

  4. Aug 30, 2013 #3

    jim hardy

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    I might have arrived at a partial answer by blind luck.

    After more reading, the black stuff is more likely copper sulfide(? .. chemistry is not my strength. )

    EDIT oops Aleph posted while I was typing THANKS !!!

    Adding just a few crystals of copper sulfate biocide from the farm supply store to my salt&vinegar solution turned the black stuff to a copper color, albeit a dull one.
    Rinsed it in baking soda then applied flux and it readily took solder .

    That has rescued a hundred dollar extension cord (200 ft #12) that only needed a new receptacle end.
    Total expenditure:
    $0.59 for receptacle
    $0.19 for outlet box
    had everything else on hand.

    I hope this helps somebody with a car , boat or household repair.

    Industry needs to know if PVC stabilizers are corroding the wires they insulate - it could cause something that's important to fail.

    old jim
  5. Aug 30, 2013 #4

    jim hardy

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    Thank you Aleph I didn't think of ammonia and don't know why

    will try that too. Makes perfect sense.
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