Need help, just started at a health club that switched from chlorine to salt and has since experienced significant corrosion issues in their pool heater since. My first day on the job was asked to make a recommendation on staying with salt vs going back to chlorine. The GM AGM and maintenance tech all have differences of opinion. As near as I can tell the biggest issue was over-salting the pool causing corrosion and the old heater (which is now being replaced) was copper not nickle-copper.
Has anyone ever had an serious corrosion issues with a properly balanced salt water pool and a nickle-copper heater?
Pools designed for salt rarely have issues with it but retro-fitted pools can have pretty big issues. Salt pools are still just chlorine pools, the only difference is you electrically "crack" salt to get chlorine rather than use gas. liquid, whatever.
Cupro-nickle heat exchangers are quite resistant to regular chlorine levels and occasional shocking but not foolproof. I've had to get them re-tubed a few times (though three-four times over 30 years isn't what you'd call onerous). Just make sure the tubes really are cupro-nickle and not just copper or they'll live a short life. I couldn't authoritatively say if cupro-nickle will last long with salt but I think that as long as you stay on top of that langlier index you should get some decent lifespan.
If plate and frame heat exchangers come up as a possible replacement do NOT contemplate stainless steel. Those are great for domestic water with low chloride levels but rarely last more than a couple of years in pool environments. You'll have to go with titanium plates ($$$$) and the heat exchange rate of titanium is much lower than cupro-nickle or stainless (which is also lower than cupro-nickle). I had one hot tub go from 8 hours to heat (53F to 104F) to 12 hours with a stainless plate and frame and finally now 16 hours with the same number of titanium plates.