# PVC Wire Insulation

by jim hardy
Tags: insulation, wire
 Sci Advisor P: 3,003 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
 Engineering Sci Advisor Thanks P: 6,041 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 - but anything that reacts chemically with the oxide or sulfide will probably react with metallic copper as well. http://en.wikipedia.org/wiki/Copper_monosulfide http://en.wikipedia.org/wiki/Copper(II)_oxide
 Sci Advisor P: 3,003 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