Salt VS. UV
First, there is a wide spread misunderstanding with regard to a salt system on your pool or spa. Some believe that with a salt system they have gotten away from chlorine. In fact, the cell in the system converts salt to chlorine. Furthermore, there is an additional layer of saline added to the water making it a corrosive environment.
A UV system for your pool or spa adds nothing to the water. As the water passes by the lamp it is sanitized, leaving a clean, clear environment. Furthermore, a UV system will allow you to reduce your chlorine to drinking water standards. Therefore, not only is your pool water free of corrosive content, it has the lowest chemical content available.
However, if you have a salt system do not despair. By adding a UV system to your salt system, you can dial back the chlorine generation thereby reducing the chlorine content and saline.