Galvanic corrosion is destructive and can amount to costly repairs. One of the easiest and most cost-effective ways to prevent corrosion is to install a DC bonding system. This bonding provides an electrical path between all the metals on your boat, which come in contact with water, to a sacrificial anode. The reason we bond a sacrificial anode, (usually zinc) to our vessels on the hull under the waterline is to provide an electrical path between metals that are connected electrically through electrolyte fluid to a higher freely eroding material. This allows the zinc to be consumed first over all the other materials on your vessel.
In many instances, the bonding system is installed and forgotten. Which begs the question, “how do I know I am protected by my zincs?” It only takes one bad, loose or corroded connection and everything beyond that point is unprotected. The first thing to do is have a Corrosion Survey. A technician will use a Corrosion Test Meter , with one probe attached to your boat (a through hull, for example) while a silver chloride half cell is thrown over the side of your vessel and immersed in the water. The readings will tell you whether you have enough zinc still available, if there is stray current around your vessel or if there is a broken bonding wire anywhere along the bonding strip or chain.
Vessels that are taken out of the water annually usually have enough zinc for the season. If your zincs are visible from the dock and they look to be in good condition, this would be an indication you are protected.
Have you had a corrosion survey or bonding inspection done lately?