An expert on plating told me that all plating is porus, because of the gas bubbles formed during plating. So seawater may still penetrate. Could try sealing the gold plating with Marine Awatrol, and polish while still wet. Works well on old, faded, car finishes.

The car trade extended the life of their chrome plating, by using a process that produced a micro cracked finish. I believe it prevented cathodic corrosion.

Philip