I recently spoke to a CAT diesel expert who services diesels all over the province. He told me that deep in the salt mines, the diesels become encrusted with salt but it chips off and the metal underneath is perfect like the day it was built. The crucial missing component is water due to the dry environment.
The same units on the surface are rusty as heck and require persuasion to remove bolts and such due to the extreme rust from the atmosphere and salt dust.