How do I clean calcium scale off a salt cell?

Soak it in diluted acid. Rinsing only removes loose debris, but the white, crusty calcium scale is chemically bonded to the cell plates and needs an acid soak to dissolve it. Use a 4:1 water-to-muriatic acid mixture or a commercial cell cleaner, submerge the cell for 10-15 minutes until bubbles stop, then rinse thoroughly. Wear gloves and goggles, never scrub with a wire brush, and always add acid to water.