Natural stone is safe to use as pool coping on a salt water pool, however, preparation is key.
The pool coping should be sealed prior to installation on all six sides (or at a minimum the underneath and the top) with a premium penetrating/impregnating sealer, such as Dry Treat Stain-Proof or Dry-Treat 40SK – see Sealing section. As extra protection, your installer could also use a waterproofing membrane . Regular hosing down of your coping is recommended to wash away any salt crystals that may form.
Drainage design and waterproofing should be considered prior to installation as part of a broader ‘moisture management plan’. If laying in a damp area and to assist in dealing with efflorescence and other moisture related issues, we recommend coating the substrate (ideally the bedding screed) with a waterproofing compound/membrane prior to tile installation. You can also seal the underside of the coping with a premium impregnating sealer, such as Dry Treat Stain-Proof – see above.