Originally Posted by Alastair

In my experience--And this is based on UK weather conditions, with moist air for many months of the year, Steel brake-lines can also corrode From The Inside..

Brake-fluid can absorb moisture from the air, this can cause corrosion inside a pipe that otherwise appears perfect...

Personally, and based on my experiences, I would replace with Cupro-Nickel pipes,-- nipples and unions are cheap and a flaring tool isnt expensive....
--I wouldnt hesitate--just renew them, job done...

Forming Cupro-Nickel into shape is much easier than steel pipe and a great job can easily be done in the same time-frame as removing a good pipe off a donor and re-fitting to the recipient....
--Best part, it'll Never corrode from either inside Or outside, ever again!

Good brakes can mean the difference between life and death....