Choosing Between Magnesium and Aluminium Anodes

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Corrosion is a nightmare for boat owners as it causes damage to the boat hull, propeller and other metals used to make the vessel. Corrosion occurs when the boat's metallic surface comes into contact with oxygen ions present in water which leads to the oxidation of the metal surface. Once the metal is oxidized, it loses its resistance to corrosion. It is for this reason that sacrificial anodes such as magnesium anodes and aluminium anodes are used to prevent the corrosion by providing the protective electron necessary to counter the oxidation process. For individuals looking to install anodes on their boats, below are four useful tips on choosing the right anode to use.

What to consider.

Nature of the water: Before deciding on which sacrificial anode to use on a boat, the first consideration is the type of water in which the boat gets used. Magnesium anodes are only suitable for use in freshwater and never in any other kind of water. However, aluminium anodes are multi-purpose since they get utilized in any type of water; be it in freshwater, brackish water, polluted fresh water or salt water. It is essential to note that using a magnesium anode in any other kind of water -apart from fresh water- will be a futile effort in preventing corrosion.

Longevity of the anode:  Magnesium and aluminium have different electrical capacities thus meaning that despite both being applicable in fresh water, they do not have the same endurance. Magnesium anodes have a small current capacity, and thus they offer more protective electrons faster. As a result, the anode gets depleted just as quickly. Aluminium anodes, on the other hand, have a relatively higher current capacity than the latter and thus tend to last longer in fresh water. In a nutshell, an aluminium anode lasts five times longer than a magnesium anode.

The cost of the anode: The price of the anode to be used is also a determining factor when choosing between aluminium and magnesium anodes. Magnesium anodes are more expensive than aluminium anodes.  Aluminium is less expensive because after using the anode for a short period, it forms an aluminium oxide layer on its surface; preventing it from giving out electrons. Another reason for the price difference is because magnesium anodes are more efficient in fresh water than aluminium anodes.

Metal that needs protecting: Different materials such as steel, aluminium, and bronze are used to make boats. In fresh water where either the aluminium and magnesium anodes get used, both can provide protection for any metal. However, the choice between the two anodes gets determined by which one is more efficient in preventing corrosion.