A Guide to Choosing the Perfect Boat Anodes

Imagine this scenario: you’ve just bought a new boat. The purchase was a significant investment, and you want to make sure the boat stays in good condition for as long as possible.

But after just a few months of using it, you notice something is wrong: your boat shows signs of significant corrosion.

How can you prevent corrosion from destroying the metal components of your boat? Depending on the type of corrosion on your boat, you might need boat anodes.

That’s good to know, but there are multiple types of boat anodes available. How do you know which kind to buy?

Keep reading to find out.

Boat Anodes

What Are Boat Anodes?

Boat anodes are pieces of metal you attach to parts of your boat that sit underwater. Boat anodes prevent other pieces of metal on your boat (like the propellor or the rudder) from corroding.

But how do they do that? To understand how boat anodes work, you first need to learn about galvanic corrosion.

Galvanic Corrosion

Galvanic corrosion takes place when there are two different metals placed in water. The metals and the water form a sort of battery in which an electrical current flows between the metals.

The metal that has more negatively charged ions will give up these ions to the metal that has less negatively charged ions.

The metal giving up its ions is called the anode, and the metal receiving those ions is called the cathode. Over time, the anode begins to corrode because it is losing its substance in the ion exchange.

You can figure out which metal will become the anode by consulting this galvanic table. In this table, the metal listed higher than the other one will become always be the anode.

Sacrificial Anodes to the Rescue

Galvanic corrosion can cause serious damage to your boat in just months. Thankfully, sacrificial anodes can prevent this damage.

Sacrificial anodes are made of metals that rank lower on the galvanic table than the metals on your boat. These anodes take all the corrosion on themselves, protecting the other metals on your boat. This technique is referred to as cathodic protection.

There are three metals used as sacrificial anodes on boats: zinc, aluminum, and magnesium.


Zinc is the most commonly used metal for anodes, so much so that boat anodes are sometimes referred to as “zincs”.

However, they are currently declining in popularity because aluminum anodes can outperform zinc anodes. Zinc is also a heavy metal, which means it’s damaging to the environment.

Despite these facts, zinc anodes still have their uses. They perform well in saltwater conditions, and they are the best type of anode to use for when your boat will be docked in seawater for a long time.


Aluminum is gaining popularity as a boat anode for multiple reasons.

First, aluminum is more versatile than zinc: it can be used in salt water, brackish water, and freshwater environments. An aluminum anode can also last up to 50% longer than a zinc anode in saltwater.

Lastly, aluminum isn’t as harmful as zinc is to the environment.

Aluminum is not immune from disadvantages, though: the final metal on our list still outperforms it in freshwater environments.


Magnesium anodes perform the best in freshwater, and out of the three metals listed, magnesium is the least harmful to the environment.

However, there are some drawbacks to magnesium anodes. They have the shortest life span out of any of the metals and shouldn’t be used in saltwater due to the water’s high conductivity.

Installation and Replacement

Before you go and buy whichever sacrificial anode is best for you, you should also know how to install and replace the anodes.

The most important areas on a boat that need anodes are the hull, rudder, and propeller.

When you go to attach the anodes, make sure that they make good surface contact. This means that you’ll want to remove any paint in that area and clean the surface before attachment.

Anodes should be changed out once a year or at 50% corrosion. When your boat anode has reached this point, it will weigh half of its initial weight.

The amount of time it will take for your boat anode to reach this point depends on a variety of factors, including the type of boat, how often it’s used, and the water it’s in.

Practices to Avoid

Within the world of boat anodes, there are a couple of practices you should avoid to ensure that your boat anodes can do their job properly.

You should never paint over your anodes, as this will prevent them from working.

You also shouldn’t mix anode types, like having both zinc and magnesium anodes on your boat. Since each metal ranks differently on the galvanic table, one of the anode types will begin to act as a cathode instead.

Lastly, you should know that it ispossible to attach too many anodes to your boat. Overprotection can lead to many different issues.

You can avoid overprotection by asking your provider to help you figure out how many you’ll need.

Buy the Boat Anode Right for You

This guide should have helped you get an idea of which boat anodes would be best for you. Remember that the type of water your boat will spend its time in is crucial in making this decision.

If you’ve already decided that zinc anodes are the best option for you, you can order yours today at our online store!