I'm not sure I understand the salt doesn't add to the corrosiveness. Boats are designed to be around water, however when used in salt water they have much more and quicker corrosion. Perhaps it's something else in the ocean water but it's far more destructive to equipment, pumps, engine water jackets, hoses, etc. than fresh water is. I used to live on a boat in the ocean and the water is incredibly destructive.

Also doesn't areas that use road salt cause more damage to car undersides ? I understand that the car is not treated to handle a chlorine water environment or salt.

But I would think that any type of protection/galvinazation for pool equipment metal will eventually breakdown or have a few places that protection wasn't applied correctly and when that salt does get into contact with the metal that it might corrode quicker than if it was just water with very low salt levels would ?