Potentially. It is one of the many reasons for the move towards TN-C-S
earthing, where the earth is carried by the neutral conductor.

Uh, that's TN-C and isn't allowed in consumers' installations.

I was talking about the incoming supply. I certainly wasn't proposing TN-C.

Rusting/corrosion of steel armour wires is not a problem, galvanizing
protects well.

It's more of a problem with the termination, where rusting can lead to high
earth loop impedence at the connection point. The armour itself shouldn't be
a problem.

Christian.