My 8”x3” grounding plate doesn’t look right. I know some are porous bronze but this looks like stainless and is non-magnetic. It is only connected to mast and stays not bonded to thru hulls for lightning protection. It looks like severe wormy stray current corrosion even in the machine screw heads. I pull my boat every 2 years and the two prop shaft zincs are about 1/2 gone. I never plug my boat into shore power nor rarely do my boat neighbors. Thoughts?