-- The Home Page of the Finishing Industry
23+ years of serious education, promoting Aloha,
& the most fun you can have in metal finishing smiley
    no popups, no spam
on this site
current topics
topic 6024

Preventing Copper From Discoloration Inside PVC Cable.

A discussion started in 2000 but continuing through 2017


Q. Hi,

I have a cable plant, the problem I am facing is that in spite of using bright annealed copper the color turns black or green after the P.V.C coating within 20 to 25 days.Can you suggest any chemical that may be used during the copper drawing or annealing process which can protect the copper from oxidation inside the P.V.C and also does not effect the current carrying capacity.

Any person who can rectify this problem may please help.

Vaibhav Sondhi
cables - Delhi, India.

Wire Technology
from Abe Books



A. Dear Vaibhav Sondhi,

Would you please tell me detailed process of P.V.C coating; does it need high temperature? If it does, how high?

I just want to know about the current discoloration-proof treatment that is used. You know BTA (benzotriazole) is always used for copper anti-discoloration, but sometimes it is not good enough to prevent discoloration for a longer time. I have been studying copper discoloration-proof for many years, and there are several kinds of anti-discoloration products, please tell us your present problem as detailed as possible.


Ruifeng Bai
- P.R.China


A. Please add copper passivator to solve this problem.

- Tirunelveli, Tamilnadu, South India

February 9, 2009

Q. Mr. Bai,
Can you please explain in details about discoloration phenomenon during & after insulation of copper conductors.

Anil Kapoor
copper cables - India

July 20, 2016

Q. Hello!

I am facing the similar problem of getting copper black while coating PVC. Have you people already discussing the same problem get any solution so far? If anyone knows please help me I will be grateful.


Iqra Ayoub
- Lahore, Pakistan

Hi Anil; hi Igra. The black is certainly an oxide or sulfide; sulfur certainly turns copper black, as has been reported thousands of times in the Chinese wallboard scandal. If there is a way to limit exposure to sulfur and high temperatures, that probably would help. Ruifeng probably can't condense his "many years of study of this subject" into a paragraph of two that covers all situations and which will turn us all into experts able to deal with a general issue that he has spent years on, so ...

As he requested of Vaibhav, please tell us the details of your own particular situation. What are you presently putting on the copper as corrosion inhibitor, benzotriazole? Any other tarnish inhibitor, like a chromate? Does this happen on every meter of cable, or only occasionally. How big is the cable? What temperature is the PVC. What does the installation look like -- is it a continuous wire drawing and PVC coating line? I am fairly confident that someone with years of experience can be helpful to us towards solving a carefully detailed highly specific problem, even though unable to educate us into being experts ourselves. Thanks, and get back to us with details please!


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

This public forum has 60,000 threads. If you have a question in mind which seems off topic to this thread, you might prefer to Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.