Dave hi, sorry, I wasn't meaning to be obtuse !
Brake pipes are manufactured in original equipment mode, to fail on rust, albeit Lexii don't seem to go so rapidly.
The structural underside to Lexii seem to be very robust and made of sterner stuff than most cars.
My g/fs Mazda 323f albeit now 17 years old, is failing with rust at the back-end ( brake pipes renewed long ago ) due we think to a previuos owner parking the car rear facing the sea for many years and getting the brunt of salt air, especially when stormy !
Malc