I don't know... I'm not an expert on the subject, but IMO saltwater is reactive enough to break that down and leach it into the water. grounding probes are usually titanium I believe.
Something else to consider, I never thought about it but my buddy was explaining to me. If you reach your hand into a tank with loose voltage, you act as the ground which is why you get the sensation of being shocked. Otherwise the tank water is not grounded and voltage does not pass through. By adding a grounding probe, you're adding a permanent ground and that voltage will therefore always be channeled through the water.
IMO, make sure your tank is on a GFCI first and foremost, skip the grounding probe, and replace the defective heater.
I'm sure my understanding with the grounding of voltage is rough around the edges, so someone correct me if I'm off base here.