The Importance Of Zinc Anodes In Boats & When To Change Them


When two different types of metal are electrically or physically connected, and then immersed in seawater, the metal becomes a battery. Some form of electrical current is now flowing through this battery. Electrons that created this current are powered by one of the metals giving up it’s metal ions to the ocean water. This process is known as galvanic corrosion, and when it’s left unchecked, it destroys underwater metals with ease.

In boats, galvanic corrosion usually occurs between a bronze or aluminum propeller that sits on a stainless steel shaft. Unfortunately, this also puts any metal hardware, like rudders, rudder fittings, and stern drives at risk as well. Galvanic corrosion is counteracted when a third metal, that’s even faster to give up it’s electrons, is added to the circuit. This piece of metal is referred to as the sacrificial anode. This sacrificial anode is usually made up of zinc. Due to this fact, most boaters just refer to the sacrificial anode as the zinc, or zincs.

Maintaining the anodes of a boat is of the utmost importance in order to keep the boat running well in the long run. When an anode is missing, or almost wasted away, whatever metal component, or components, it was installed to protect will surely dissolve sooner than later.


How Much Zinc Is Required To Protect The Components Of A Boat?  

The surface area of a zinc anode determines how much protection it can provide. The surface area, along with the kind of metal being protected and chemical makeup of the water help decide the protection the anode will provide. Check the metal that the zinc was installed to protect regularly. If the metal show signs of corrosion even with the zinc installed then you require an anode with a larger amount of surface area.

Zinc should be replaced by the time half of the anode has been lost to corrosion. This shouldn’t be more often than once a year. Ultimately, the lifespan of a zinc anode depends on its weight. If you find yourself having to replace the zinc anode more than once a year, than you need an anode with more weight.

In most cases, you shouldn’t have to decide the size of anode the boat needs. Instead, you’re just replacing depleted zinc anodes with new ones of the same specifications. Make sure you check all of the zinc anodes on your boat at least once a year, and replace any that have been depleted half way.

Zinc Alternatives

There are alternative anodes to protect metal hardware on the boat from galvanic corrosion besides zinc. One that is becoming increasingly popular, and is sure to surpass zinc anodes is aluminum anodes. These aluminum anodes even protect aluminum hardware due to the type of alloy the anode is. The only reason that aluminum anodes are not more popular than zinc anodes is that the price is higher and proves no true benefit to the boat owner.



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