What Are Anodes On A Boat Used For?

What Are Anodes On A Boat Used For?

By: SamComments: 0

Boat anodes are an essential part of the boat maintenance cycle as they protect underwater metals from galvanic corrosion. Also known as sacrificial anodes, boat anodes generally come in three metals - aluminium, magnesium and zinc.

The Purpose Of Marine Anodes

As mentioned above, a boat anode purpose is to protect areas of the boat from corrosion. Galvanic corrosion occurs when two dissimilar metals are immersed in a conductive solution and are electrically connected.

We recommend replacing anodes when they are half eroded or dissolved, which is typically once a year. The speed in which anodes dissolve depends on a range of factors including usage, location (of your boat), water temperature and the quality of the anode itself. For example, MG Duff’s zinc anodes have a high zinc content, ensuring they provide maximum protection for a longer period of time. 

Without anodes, underwater metals are at risk of galvanic corrosion - which could in turn lead to a hefty repair bill.

Traditionally, anodes have been made from zinc but are now widely available in aluminium and magnesium, which we’ll talk about below.

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The Types Of Marine Anodes

Anodes come in a whole host of shapes, sizes and metals. 

The first question we ask anyone who visits our Rochester store looking for an anode is what water they will be using their boat in, as this will dictate your choice of metal.

Let’s take a look at the main three metals:

Aluminium Anodes -

Aluminium anodes are suitable for use in salt and brackish water. Their higher electrical capacity enables them to be smaller and more compact than their zinc and magnesium counterparts. 

Magnesium Anodes -

Magnesium anodes should only be used in fresh water, where their longevity is increased by a lower open circuit potential. Magnesium anodes are much lighter than zinc anodes, which can result in energy and fuel savings.

Zinc Anodes -

Like aluminium, zinc anodes are suitable for salt water use. Zinc anodes have a higher density and structural composition, so provide significantly higher impact strength in some areas.

Anodes are specifically designed for different areas of the boat, including the engine, hull and propeller shaft in order to provide maximum protection.

Why are aluminium and zinc anodes suitable for salt water use?

As electricity travels through salt water faster, you will need a heavier metal that dissolves at a slower rate. 

Why are magnesium anodes suitable for fresh water use?

A parallel opposite to salt water - electricity does not flow through fresh water quickly, so you will require a softer metal to require this.

So what about brackish water anodes?

Brackish water sits in between fresh and salt water. For brackish water, we’d typically recommend you opt for an aluminum anode as they are cheaper and provide better protection than their zinc counterparts.


Some of our most frequently asked questions are ‘what are anodes used for on boats’, ‘what do boat anodes do’ and ‘why do you need anodes on a boat’ - which is the reasoning behind this blog post.

If you’re looking for some new anodes, why not take a look at our excellent range of aluminium, magnesium and zinc anodes? All of our anodes are sourced from market leading brands including MG Duff, Tecnoseal and Piranha, ensuring they’re of the finest quality.

If you have any questions, our highly experienced crew are here to help. Our Rochester store is open seven days a week and we’re also contactable via email, telephone and even Facebook.


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