Take a look at the difference in the limestone sills on the left and right side of the image below.
The one on the left is new and the one on the right is about 70 years old, having spent those 7 decades directly exposed to the ocean. The erosion of the limestone on the right is from this exposed to salt-laden mist from the sea.
Here’s a closeup:
Similar 70 year old limestone sills on the opposite side of the building (not facing the ocean) look great.