Well, as to surface burns from salt water, I live a block and a half from the beach in So. Calif. We get a lot of salty mist coming in during certain seasons. No damage from it that I can detect.
The sodium content of the municipal water is a whole 'nother kettle of fish. We have problems with trees that cannot tolerate it.
Hard water leaves white scum on leaves but it doesn't seem to damage them. But ours isn't as hard as other folks. Maybe they have more info.
Joanie