Anodes and Zincs

A galvanic anode is the main component of a galvanic system used to protect buried or submerged metal structures from corrosion. They are made from a metal alloy with a more "active" voltage than the metal of the structure. The difference in potential between the two metals means that the galvanic anode corrodes, so that the anode material is consumed in preference to the structure. The loss (or sacrifice) of the anode material gives rise to the alternative name of sacrificial anode.

Corrosion is like the uninvited guest who always shows up hungry. At some point, you forget about serving this goat a meal and dish out snacks and junk food to keep him away from the roast beef. With corrosion, you feed the unwelcome guest excess electrons instead of Twinkies. These electrons come ready to eat, “packaged” in the form of what are called sacrificial anodes. Corrosion eats the anode (the Twinkie) instead of your sterndrive, prop shaft or raw water through-hull (the good stuff) because anodic metals dish out electrons as freely as Grandma dishes out Thanksgiving dinner. Know that with each electron consumed, a minute bit of the anode’s metal is consumed instead of a bit of your boat or drive’s metal, hence the sacrificial moniker.