“The “copper/nickel” BMW brake lines you mentioned are stainless steel ,, those are the two ingredients you add to steel to make stainless.”
LOL, thought about that after I posted inquiring about them. Stainless it is.
Automotive brake lines are indeed manufactured from cupro-nickel on some high-end cars. Volvo, Rolls Royce, Lotus, Aston Martin, Porsche and Audi all use Copper-Nickel alloy C70600, an alloy of 90% copper and 10% nickel.