MG Duff Shaft Anode - 28mm (1 1/8")

Anode suitable for a 28mm prop shaft (1 1/8").

A zinc shaft anode is a type of sacrificial anode designed specifically to protect the shaft of a boat or other marine vessel from corrosion caused by galvanic and electrolysis reactions. These anodes are typically made from zinc because of its effectiveness in saltwater environments, and they are used in applications where a metal shaft is exposed to water (often the propeller shaft) and vulnerable to corrosion.

Key Features of a Zinc Shaft Anode:

1. Sacrificial Protection:

   • Like other sacrificial anodes, a zinc shaft anode works by corroding in place of the metal it’s protecting. Zinc is more electrically active (less noble) than the metals typically used in propeller shafts (such as stainless steel or bronze), so when both metals are in contact with water, the zinc anode will corrode first, preserving the shaft from damage.

2. Material (Zinc):

   • Zinc is commonly used in marine environments because it’s highly effective in saltwater conditions, where galvanic corrosion is more pronounced. Zinc anodes offer good protection against corrosion of the shaft and other underwater metal parts.
   • However, if your vessel operates in brackish or freshwater environments, aluminum or magnesium anodes may be a better choice, as zinc is less effective in these conditions.

3. Location and Installation:

   • A zinc shaft anode is typically installed directly on the propeller shaft, often by clamping it around the shaft or attaching it with a bolt or screw. The anode is positioned where it can make good contact with the surrounding water, ensuring effective protection for the shaft.

4. Protecting the Propeller Shaft:

   • The primary function of the shaft anode is to prevent corrosion on the shaft itself and other submerged metal parts, such as the propeller or stern tube. Corrosion can weaken the metal, affect performance, and even lead to failure over time. By installing a zinc anode, you can avoid costly repairs and extend the lifespan of the boat’s propulsion system.

5. Corrosion Resistance:

   • Galvanic corrosion occurs when two dissimilar metals are in contact with an electrolyte (like seawater). If no sacrificial anode is used, the more noble metal (the propeller shaft, for example) will corrode over time. A zinc shaft anode prevents this by sacrificing itself to protect the shaft from the damaging effects of galvanic corrosion.

How Does a Zinc Shaft Anode Work?

When the zinc anode is placed in water, a small electrical current is created between the anode (zinc) and the metal shaft (usually bronze or stainless steel). Because zinc is more electrically active, it corrodes in place of the shaft, thus protecting the shaft and any other attached underwater metals (like the propeller or rudder).

The process of corrosion is what allows the zinc shaft anode to function. The zinc material is slowly worn away over time, but as it does, it prevents the shaft from deteriorating, effectively prolonging the life of the boat’s key components.

Why Use a Zinc Shaft Anode?

• Protects the Shaft and Propeller: Prevents corrosion on the propeller shaft, which could otherwise lead to premature wear, pitting, or failure.

• Affordable and Easy to Replace: Zinc anodes are relatively inexpensive and easy to replace, making them a cost-effective solution for protecting your boat's underwater components.

• Essential for Saltwater Use: Zinc is the best choice for vessels operating in saltwater, where corrosion risks are higher. In these environments, using a zinc shaft anode is essential for protecting the boat’s underwater metals.

• Prevents Expensive Damage: Without an anode, the shaft and other metal parts can experience severe corrosion, leading to expensive repairs or even total failure of the system.

Maintenance and Replacement:

• Regular Inspection: It’s important to regularly inspect the zinc anode to check how much it has corroded. If the anode is more than halfway gone, it should be replaced.

• Replace Annually: In most cases, zinc shaft anodes should be replaced at least once a year, especially if the boat is in the water year-round or if you notice increased corrosion.

• Check for Loose Connections: Ensure that the anode is securely attached to the shaft. A loose connection may result in ineffective protection and reduced corrosion prevention