Quote Originally Posted by russ t View Post
Thanks Janet for the "bump". I've been leaning toward SWCG for sanitizing, but the local pool shop said it would be corrosive on my automatic cover and pool deck/railings/copings. Any truth to this?
Yes!

1. The salt itself has issues of attacking the cement in the plaster and deck materials. Buyers should be aware that if you have salt water above 2800 ppm, (often 4000 to 5000 ppm), you will need to reseal your coping every year, especially if it is a porous stone like limestone or travertine. Otherwise, the salt will dry and start to etch the coping. Besides sealing the stone, it is also advisable and an added precaution to hose down the coping at the end of any swim day with fresh water. Although the salt water in the pool may not be corrosive at levels of 3000-3500 ppm, when that water hits the coping and evaporates, it leaves pure salt behind. The pure salt is corrosive and is the main cause of the corroding coping. Most autocover manufacturers now void their track warranty if a salt system is used.
Deck corrosion seems to be more of an issue in areas with infrequent summer rain, and natural stone decks. Arizona -- which your IP address indicates is your likely location -- is DEFINITELY an area where you could have a problem with deck corrosion. But I think the warranty issue with the cover mechanism is your bottom line.


I also found this information:
1. A common misconception is that saltwater is more corrosive than chlorine, but 4ppm of chlorine is 10 times more corrosive than 4,000 ppm of salt.
I don't think this is true. Do you have a reference or link?