3 Consequences of Anode Overprotection

Magnesium and aluminium sacrificial anodes help to protect the metal parts of a boat from the effects of corrosion caused by the exposure to water. This risk of corrosion and damage is why it is important to protect the metal parts of your boat with anodes. However, it is also possible to overprotect your boat. Overprotection occurs when the surface area of the aluminium or magnesium anodes too large compared to the metal material the anode is protecting. Below is a guide to some of the effects that overprotection can have on your metal boat. 


Embrittlement is a technical term which describes a surface which retains its rigidity and hardness but when it very brittle and easy to break. Boats which feature steel parts are especially susceptible to the effects of embrittlement. The electrical reaction which happens in the space between the steel parts and the anode causes hydrogen atoms to be released. These hydrogen atoms are small enough to penetrate the surface of the steel, compromising its structural integrity.

Damage to Protective Coatings

Boats with often have several coats that perform different jobs. The first layers applied to the exposed metal on a hull are normally protective coatings which help to stop the corrosive action of water. The top coatings are normally applied for aesthetic purposes. If the anodes are overprotecting the hull of your boat, it may begin to have a negative impact on these various coatings. For example, the coatings may begin to peel away. This occurs because of the hydrogen ions which form as the anode interacts with the water. Unlike hydrogen atoms, ions are very large and cannot penetrate the metal surface of your boat and instead accumulate between the coating and the surface of the metal, causing the coating to peel away.

Increased Numbers of Barnacles

Overprotection makes the area around your boat to become alkaline. This alkaline water provides a great environment in which barnacles can develop. If your boat is overprotected, you may see a rapid growth in the number of barnacles on the hull of your boat. Barnacles may cause further damage to your boat.

To prevent these issues, it is very important to attach the right type and size of anode to your boat. If you spot any of these signs that your boat is overprotected or if you are unsure about the right size of anode to use, contact an anode supplier for further information.