Corrosion

@koestner Is ljgerens really Walter White?

No, but I have been known to go by the pseudonym Heisenberg.

Is ljgerens really Walter White?

Here's one explanation...

https://www.audioasylum.com/audio/cables/messages/10/108143.html

DeKay

The green color is not an oxide of Cu. There are 2 oxides of Cu, Cu2O and CuO. CuO is black and Cu2O is a reddish brown color.

Copper sulfate (CuSO4) typically does not form on audio cables. It needs the presence of sulfuric acid and an aqueous environment to form. Actually CuSO4 is white in its anhydrous form but turns blue when hydrated.

The green color on Cu is due to either the formation of hydrated Copper Carbonate Cu2CO3(OH)2 or the hydrated form of Copper Chloride CuCl2(2H2O). These would typically not form on audio cables because they require the presence of an acid. However Copper Chloride can form on cables that have PVC as their insulating jacket. PVC degrades on exposure to UV and/or heat and undergoes an autocatalytic dehydrohalogenation degradation process which produces hydrochloric acid (HCl). The HCl can react with CuO on the surface of the Cu conductor forming copper chloride (CuCl2). In the presence of moisture (H2O), the CuCl2 becomes hydrated to CuCl2 (2H2O) and produces the green color.

This green color was widely seen on Monster Cable back in the day and was due to a problem in their manufacturing process. Monster Cable used a PVC jacket and If the PVC jacket did not have the proper stabilizers, it can start to degrade quickly.

 Ive noticed the same on a couple of ads for Analysis Plus Oval 9. I didn't purchase for that reason. For as much as I (we) obsess over the slightest things in our systems seeing a green copper wire just wouldn't work for me.

I spoke to Gabriel at Shunyata 10 years ago about this and was told there is nothing to worry about.  10 years later. they still are fine.

Black and or Green.

"Both colors are caused by oxidation as the copper reacts to elements in the environment. The green oxidation is commonly seen when pool chlorine is stored in the same room with electrical equipment and minimal ventilation, producing copper sulfide or hydrated copper sulfate. Jun 16, 2018."

Where you live and the environment is the biggest contributor to "GREEN". A product called NoCo is used on battery terminals, with great success for over 75 years. If you can minimize the O2 on the copper you can control the oxidation. The product is also conductive and semi-dries. It will last around acid battery terminals as long as you keep them treated. I've seen soft top batteries that were 50 years old.. No GREEN..

I'm with jasonbourne52, green is no good, I tossed a bunch of wire through the year because of "Green". I'm a mechanic, I see it all the time. I do a lot of rewiring because of aluminum wire with copper clad. The insulation is a problem too. Air tight is suppose to be air tight. That goop they use on connections works too.. No green in tractor trailer rigs when I'm done. I hate the ones that work on the coast and around salt...  

Stereo cable, I use what ever the club is using. OCC weaves and ribbons seem to be the big thing now. They sure sound good. NO Green so far. I paid 39 or 59.00 dollars for the PCs

@corelli :+1! Green oxidation was a problem with the old clear Monster Cable speaker wire! I had to throw away a bunch of it! No good! It didn't affect sound quality though! Not acceptable for the high-price Sunyata power cords! 

I would love to hear what the manufacturer has to say on this.  High purity copper, even when exposed in the average climate controlled home, should not suffer the fate you are describing.  Either the quality of the copper is in question or there is an abnormal reaction occurring with the insulation.  In either case, not normal and not acceptable.

Thanks!

Green on copper is never good but just call it patina and all will be well.

No, mine are like that, no worries.