I was doing some work in an old houses all wired with BX cable. The cable is old but sound. Maybe 30 years old.

I needed to tap into a box with this stuff and when I stripped off the insulaton I thought - no no - alumninum wire! But then I happenned to LIGHTLY scrape it a little and found it was copper after all. Apparently there was a thin coating of something gray on the wire covering the copper. So I scraped lightyly and tapped my new 14 guage bx to thae box.

Is that OK? I was afraid it was aluminum. I did note the copper did not seem as red in color as todays copper - it was a little paler in color but still copper.

Thanks!

 

It's called tinned copper. It's treated the same as copper. You don't need to scrape it.