The copper wire is black, so it is because of this?

We often find that in the process of installing and using wire and cable, there is a problem of oxidation and discolouration (blackening) of the conductor copper wire, many people feel that the blackening of the copper wire is poor quality, why is it blackened? What are the causes of blackening?

Wire and cable copper conductor blackening of the main reasons for the general cable copper conductor oxidation discoloration (blackening) because of product production, transportation, storage, laying, use of the process by the humid environment or rainwater into the cable conductor, so that the copper conductor and oxygen, water chemical reaction and discoloration (blackening).

Wire and cable copper conductor blackened parts and circumstances also vary: cable conductor end black or both ends intact, the middle black.

In short, there are three general causes of oxidation discolouration (blackening) of the copper conductors of cables: "water, moisture, air immersion".
Several situations lead to blackening:

Improper sealing of cable joints

Improper sealing of cable glands leads to blackening of copper conductors due to air intrusion. When packaging cable heads, most masters will use insulating tape to seal directly, in fact, insulating tape is not waterproof and there is a layer of glue on it, which will also make the cable black over time.

Damp insulation

This is very common and usually occurs at the joints of cables in direct burial or drainage pipes. If the cable joints are not made properly and the joints are made in humid climatic conditions, water or water vapour will enter the joints and the cables will blacken over time. This phenomenon is more common in the hot summer months when the humidity in the air is higher and the temperature accelerates the oxidation reaction of the copper conductors.

Irregular use

Customers laying installation process, cutting the cable without cable head sealing or non-standard construction operations lead to water into the occurrence of oxygen, will also be very easy to cause the cable black.
Several cases of black in the middle and good at both ends:

Transport environment

Finished products in the transportation process of the journey bumpy, cable insulation layer by extrusion, bump, scratching and other damage, when the cable copper conductor local damage to the place and the air in long-term contact with oxygen and moisture, it is possible to be oxidation discoloration (blackening).

Copper rod wire drawing process

Copper rods are made into various sizes of copper wire through the wire drawing process. For large drawing machine, medium drawing machine, fine wire machine process, are required to add wire drawing emulsion (lubricant), if the emulsion (lubricant) residue on the surface of the copper wire is not handled, long-term contact with the air copper wire surface will be oxidation discolouration (black).

Construction and installation

Some users do not standardize construction when laying and installing cables, which can easily cause mechanical damage; civil construction on directly buried cables is also very easy to run the cable damage, etc.. If the cable copper conductor local damage place long-term underground moisture or bare surface will produce oxidation discoloration (blackening).