To my surprise, the zincs on my Grand Banks 32 are gone after only six months of use. Before, they used to last some 18 months. Why the sudden change?
Galvanic corrosion not only depends on what is going on your Grand Banks 32, but also on all the boats surrounding yours, so it's not always easy to identify what has changed.
Fortunately, new technological advances have brought a fail-safe Galvanic Isolator (if the isolator fails, it will not leave the ground circuit open) that helps solve the very issue your GB32 is experiencing. This simple device is installed on the AC grounding connection right after the shore power outlet on your boat. The GI will effectively cut the stray DC current and eliminate the excesive corrosion your GB32 zincs are experiencing. You still need to have anode zincs, as they serve as another line of defense agaisnt galvanic corrosion.