Anode Knowledge

Guide to Marine Anodes

Marine anodes play a crucial role in protecting boats from galvanic corrosion, which occurs when different metals in contact with water create an electrical current that causes deterioration. Anodes act as sacrificial metal, corroding in place of essential components to extend their lifespan. Below is an overview of the different types of anodes available and their applications.

Types of Anodes

Hull Anodes

Hull anodes are fitted to the hull and underwater fittings of a boat to prevent corrosion of metal structures. They are essential for vessels with metal hulls or significant underwater metal components such as keels and rudders. These anodes degrade over time, protecting more vital parts from damage.

Engine Anodes

Engine anodes are used in inboard and outboard engines to protect internal metal components such as heat exchangers, cooling systems, and cylinder heads. Without proper anode protection, engines can suffer from internal corrosion, leading to costly repairs and reduced performance.

Saildrive Anodes

Saildrive units, which combine the gearbox and propeller drive system, are particularly vulnerable to galvanic corrosion. Saildrive anodes are designed to shield the aluminium casing and internal metal components from degradation, helping to maintain performance and extend the life of the drive system.

Shaft & Propeller Anodes

These anodes are designed to protect propellers, shafts, and related underwater metal components from corrosion. Shaft anodes are typically fitted as collars around the propeller shaft, while propeller anodes are mounted on the propeller boss or nearby areas where corrosion is likely to occur.

Anode Accessories

To ensure the proper installation and effectiveness of anodes, various accessories are available, including fixings, backing plates, and bonding wires. These components help secure the anodes in place and optimise their protective capabilities.

Anode Materials & Their Uses

Marine anodes are available in different materials, each suited to specific water types:

Zinc Anodes – Best suited for use in saltwater, as they provide reliable protection without corroding too quickly. They are the traditional choice for marine anodes but should not be used in freshwater, where they become ineffective.

Aluminium Anodes – Suitable for both saltwater and brackish water, aluminium anodes offer a longer lifespan than zinc and are also a lighter alternative. They are increasingly popular due to their versatility.

Magnesium Anodes – The best option for freshwater applications, as they corrode more easily than zinc or aluminium. However, they degrade too quickly in saltwater, making them unsuitable for marine use in such environments.

Choosing the Right Anode

Selecting the correct anode depends on the type of water the vessel operates in and the metal components requiring protection. Regular inspection and replacement of worn anodes are essential to maintain their effectiveness and ensure ongoing protection against corrosion.

For a full range of anodes and accessories, explore our collection at Marine Chandlery.