PVC Insulation Coating Discolors Copper Wire & Cable

A. Hi Rakesh. If a problem happens sometimes but not all the time it means one of two things: either something is varying which is causing the problem, which you ought to be able to track down (size of cable, color of insulation, degree of draw, time of day, etc.), or the process is not robust such that tiny, nearly imperceptible, variations cause problems to come & go.

Question #1: are you reliably treating the copper with benzotriazole [on eBay or Amazon] , or chromate, or other anti-oxidant? Question #2: what are the details of your situation? The idea that there is some simple step that you can take which will solve the problem irrespective of any variations in the PVC coating formulation and application method, and which will solve the problem in all circumstances, probably isn't realistic as Ruifeng Bai has noted. Sorry.

Luck & Regards,

A. Dear Vaibhav Sondhi,

Would you please tell me your 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 resistance for many years, and there are several kinds of anti-discoloration products, please tell us your present problem as detailed as possible.

Thanks,

A. Please add copper passivator to solve this problem.

Hi Anil; hi Igra. The black is certainly an oxide or sulfide; sulfur [affil links] 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 will help. Ruifeng has said that he can't condense his "many years of study of this subject" into a paragraph of two that covers all situations , 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 confident that someone with years of experience can be helpful to us towards solving a carefully detailed problem, even though unable to educate us into being experts ourselves. Thanks, and get back to us with your details please!

Thanks & Regards,