sealant that will protect stone in chlorine pool

 I am trying to educate myself on ways to clean and (http://maplered.com) hopefully seal (if not possible, at least slow down) the efflorescence at the waterline of our pool.  The coping and (http://maplered.com) waterline tile is sand (http://maplered.com) Stone (http://g603.net) and (http://maplered.com) within 2 years has developed a distinct and (http://maplered.com) unsightly white line.  The advise I have received so far is if power washing with acid doesn’t do the trick (and (http://maplered.com) it hasn’t) that glass bead pressure blasting in the only thing that will remove it.  Is there any sealant that will protect the Stone (http://g603.net) in a chlorine pool?

I’d appreciate any help I can get!!

Thank You.