People often mistakenly think AC corrosion in marinas is the biggest source of corrosion but your own boats DC is far more dangerous and far more speedy at eating metals. One of the biggest violators I find is DIY's who tap into the bonding circuit for a path back to the batteries. I had one guy who used only red wires one way, to save money, then used the DC bonding circuit for all his neg returns to the battery. Cabin lights, macerator, stereo, VHF etc. etc.. Boat had about 15k in corrosion damage... The pump or device works when they connect to the "green wire" so they think they did it right. Behind that blunder are exposed bilge pump wires in the bilge or chafed wires sitting in the bilge and the owner who thinks his mast is like the chassis of a car and uses it for the neg return for all the running lights...... DC corrosion is far worse and far faster at destroying metals than AC...