When two different types of metal are submerged in seawater, and electrically or physically connected, a battery is created. A certain quantity of current travels from one metal to the other. This current consists of electrons, which are sourced from one of the metal types. Pieces of this metal are siphoned off into the seawater, as metal ions. Galvanic corrosion is the name of this process and, if unattended to, it rapidly ruins underwater metals.
Aluminum or bronze propellers on stainless steel shafts tend to be affected the most by galvanic corrosion. Nonetheless, rudders, metal struts, outboards, stern drives and rudder fittings are vulnerable too. Galvanic corrosion is best prevented by adding an extra metal to the circuit, which gives up its' electrons faster than the other metals. This third type of metal is usually zinc, and it is referred to as a 'sacrificial anode'. Actually, many boat owners use the terms 'zincs' and 'sacrificial anodes' interchangeably.
The surface area of a zinc anode governs the degree of protection it offers. Different zinc surface areas are required, based on the types of metal used in a battery, and the water's chemical composition. However, one percent of the protected metal's surface area is fairly common.
The protected metal should be regularly examined. If corrosion is evident, in spite of the zinc, additional surface area is needed. It is vital for boat owners to maintain the zinc anodes on their vessels. Once an anode has disintegrated, or gone missing, the metal part it was fitted to protect will corrode quickly.
Zimar Zincs are the industry standard, and that is why most discerning boaters use them to protect their investment. Propeller Depot carries the entire line of Zimar Zincs, and can ship them across the world. If you have any questions on Zinc Anodes, please contact the experts at Prop Depot.