I just removed the round zlnc on my rudder today. It is a circular zinc bolted to the rudder plate with zinc on both sides. The rudder has stainless bar welded to the plain (or at least magnetic) steel blade. The blade and shaft are in good condition except for the area of the blade under the zinc. That area is very pitted and perhaps half eaten away. The boat is new to me and is 35 years old so perhaps this is to be expected or is it?