Steel to copper brake line union – safe or not?

Hey everyone,

I had a brake line repair done on my 2006 Mercedes CLK at a workshop. They replaced part of the original steel line with a copper (or copper-nickel) line and connected it using a union fitting.

A friend told me that mixing copper and steel brake lines is not recommended, and now I’m a bit worried about safety.

The connection looks properly done (flared ends, correct fitting), but I’m concerned about long-term reliability, corrosion, and whether this is actually a safe repair.

Is this kind of setup generally acceptable, or should I be asking the workshop to replace the entire line instead?

Thanks for any advice.