Selecting the Right Type of Sacrificial Anode for Your Boating Adventures

Posted on: 18 June 2017

If you're planning a life on the ocean wave and are relatively new to the marine world, you need to learn more about the exciting subject of corrosion. It's an unfortunate part of life here, but the good news is that you can use "sacrificial" anodes in order to keep such corrosion at bay. What do you need to know about the risk and how you can deal with it?

Types of Corrosion

In essence, there are two different types of corrosion at play here: The first is electrolytic, where a damaged appliance can leak currents to ground and this can rot washers, bearings and other engine components. The second is galvanic, where two connected metals are submerged in seawater and act like a battery, prompting the corrosion.

Two Different Kinds of Anode

To help keep this problem at bay, two different types of anode materials are recommended. The first is zinc, which is usually cheaper and selected more often than the alternative. It's used to help protect some of the more prominent metal components. Aluminium anodes are suitable for the outboard motors, as they can generate a protective surface film to provide good corrosion resistance. They are however prone to the previously mentioned galvanic corrosion, should they come into contact with specific metals like brass, nickel or bronze.

Much will depend on the type of hull that you have on your boat. While wood and fibreglass are of course not susceptible to corrosion, any equipment attached will be. Steel and aluminium hulls are very prone to galvanic corrosion and aluminium is liable when it is combined with some other metals. Protective paint coatings can do part of the job, but specific sacrificial anodes are best.

Determining Exposure

If your boat sits in the water for extended periods of time, then the number of anodes you will need is dependent on how much of the hull is below the waterline. If you bring the vessel out of the water when you're not using it, then you will probably only need anodes for the outboard.

Water Type

Finally, determine what type of water your boat will be encountering during the balance of its life. The type of anode that you fit will be dependent on whether you will encounter fresh, salt or brackish water.

Working out Your Requirement

Have a word with your supplier of aluminium and magnesium anodes and give them the configuration of your vessel and the type of water involved. This will determine what type of anode you need, to provide as much protection as possible.