I suppose it entirely depends how the packs are built, I've got no idea and won't pretend I do. If it's a double thickness box with a waterproof membrane should be fine for years. If that's the only skin though it's not promising.
Given the build quality issues tesla had with rust wonder how the underside of a model S would look after 10 years on our roads.
The floor pan etc. looked immaculate but unfortunately the battery is a rather expensive piece to be hanging in the salt spray. It was no worse than the rear beam on the Mazda tbf...but I can get one of those for a few hundred quid.
Welding a battery box anyone?