Solving the Mystery of PVC Wire Insulation Corrosion

In summary, there has been a noticeable increase in black corrosion on copper wire over the past decade. This corrosion prevents soldering and causes difficulty in repairing objects like headlamp sockets and extension cords. It used to be uncommon, then became more frequent on certain colored wires, and now it is prevalent worldwide. This issue has prompted questions such as whether the coating is copper sulfate and if it is caused by sulfur-bearing organotin stabilizers in PVC insulation. Some have attempted to remove the corrosion with various chemicals, but with little success. However, it has been found that adding copper sulfate biocide to a salt and vinegar solution can turn the black corrosion into a dull copper color, making it possible to solder. This has successfully rescued expensive items like
  • #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
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  • #2
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.
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  • #3
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
  • #4
Thank you Aleph I didn't think of ammonia and don't know why

will try that too. Makes perfect sense.

1. What is PVC wire insulation corrosion?

PVC wire insulation corrosion is a process in which the protective PVC coating on electrical wires degrades and breaks down, leaving the conductive metal underneath exposed to the elements. This can lead to electrical malfunctions, fire hazards, and other safety issues.

2. What causes PVC wire insulation corrosion?

PVC wire insulation corrosion can be caused by a variety of factors, including exposure to moisture, chemicals, high temperatures, and UV radiation. It can also be accelerated by mechanical stress, such as bending or twisting of the wire.

3. How can PVC wire insulation corrosion be prevented?

To prevent PVC wire insulation corrosion, it is important to choose high-quality PVC coatings that are resistant to the specific environmental conditions in which the wires will be used. Proper installation techniques, such as avoiding sharp bends and using appropriate connectors, can also help prevent corrosion.

4. How can PVC wire insulation corrosion be detected?

PVC wire insulation corrosion can be detected through visual inspection, as the PVC coating will appear cracked, brittle, or discolored. Electrical testing can also be used to detect any changes in the wire's conductivity, which may indicate corrosion.

5. Can PVC wire insulation corrosion be repaired?

In most cases, PVC wire insulation corrosion cannot be repaired. Once the PVC coating has degraded, it is necessary to replace the affected wires to ensure safety and proper functioning. Regular maintenance and proper installation techniques can help prevent corrosion and the need for costly replacements.

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