I was doing some electrical wiring on a trailer today and was surprised to see black instead of shiny copper when I cut and stripped a section from the middle of a long section of uninterrupted wire. There was literally at least 6m of uninterrupted wire on either end from where I cut!
My question is: can wire oxidize INSIDE the protective rubber? And if so, is the wire still good to use or should I be ripping it out and redoing all the wiring on my trailer?
For context: the wire is 18 AWG copper; it simply used to run current from the vehicle 4-pin connector to the trailer lights.
Here are a few pictures:
You can see two of the oxidized wires at the top; I included a new/fresh wire for comparison.
The oxidation can be rubbed off with the edge of a knife, but it's not ideal - it seems to be really easy to damage/break off the copper strands.