Replacing the Anodes and Painting the bottom

Bare steel, like the hull of this boat will rust more quickly in salt water than freshwater. Putting the anodes on the boat basically turns the entire boat into a big battery cell. In a battery cell there is an anode and a cathode. This anode will protect the steel (cathode) since the zinc will more readily release ions than steel and take the corrosion instead. Called a sacrificial anode they will need to be replaced from time to time. This cluster of photos shows the spent or sacrificed anode, a new anode and Wayne replacing one on the boat. The boat requires around 8 to 10 such anodes on various parts like the hull, rudder, and propeller shaft.

In fresh (unsalty) water this corrosive effect is much less and the anodes degrade at a much slower rate. Also the better covered or painted the steel is the slower the anodes will degrade.