Thru-Hull Fittings and Cathodic Protection

Surface corrosion of these fittings is not your worst enemy though. The items, if constructed of metal, must be bonded to the vessel’s cathodic protection system. This bonding allows the anodes, commonly referred to as zincs (they are most often but not always made of zinc) to protect your through hull fittings from corroding in the seawater they are submersed in. The bonding consists of a wire (a green wire in most newer vessels) that is connected directly to the fitting from the vessel’s bonding system. When spraying some silicone on the fittings have a close look to be sure there is a wire connected directly to each of them. If you can’t see a wire, look for a loose wire nearby as it has likely broken off. This wire must be re-attached. If you are unable to do this or you can’t find a loose wire, be sure to call a maintenance professional to take care of it. That fitting is corroding away constantly if not protected and not to be overly dramatic but, if it fails, your boat can, and likely will sink.

Silicone spray can be your best friend here too, because it helps remind you to check on these critical bonding connections.