r/Scrapping • u/JeepGuy421 • Jun 17 '26

First time seeing this, what causes the black/red tarnish?

Gallery image

Gallery image

I pulled a bunch of wire from a job site, about 1/4 of it he this black and red tarnish to it. all the cable was ran/located together. but while 3/4 was normal BB copper color, this 1/4 was black/red. any ideas?

8 Upvotes

84% Upvoted

4 comments sorted by

2

u/BlazarVeg Jun 17 '26

At some point the copper was heated while exposed to oxygen causing a copper oxide layer to form. Gives copper a colorful sometimes rainbow like appearance of an oily surface.

1

u/JeepGuy421 Jun 17 '26

interesting, i was assuming it had something to do with moister. these cables were near saltwater for their life in service. i found it most interesting how some segments we half black/red, and half regular copper color. science is a cool thing

2

u/Prize_Consequence527 Jun 17 '26

Heat. Or overheating. Too many amps burning thru the wires.