Sacrificial Zinc Anodes
Zinc anodes and other kinds of sacrificial anodes are an important component of your boat. They greatly reduce corrosion, keeping your boat in working order. » Read More
Learn More About Sacrificial Zinc Anodes
Contents
What Are Zinc Anodes for on Boats?
Zinc anodes are “sacrificial” attachments that protect submerged structures from corrosion. They’re most commonly referred to as zincs or anodes. They play a significant role in prolonging the lifespan of your boat and should be considered a regular part of maintenance. Read More
Galvanic Corrosion and Electrolysis
There are a few different types of corrosion that are prevalent in the boating world. Oxidation is one type of corrosion that most people are familiar with, resulting in a dull layer on your aluminum or stainless steel. Oxidation isn’t limited to metal, as gelcoat surfaces can oxidize as well. Read More
How Anodes Protect Boats
Zinc anodes for boats can effectively reduce both galvanic and electrolytic corrosion. Zincs are considered a sacrificial anode, meaning they will deteriorate and corrode instead of the important parts of your boat corroding. In the case of galvanic and electrolytic corrosion, sacrificial anodes work by giving up their electrons before the materials they’re protecting. As a result, they will oxidize and deteriorate while the expensive metal parts of your boat stay intact.
Zinc vs. Aluminum vs. Magnesium Anodes
Sacrificial anodes can be made of different materials for different uses. The three general metals used are magnesium, aluminum, and zinc. These metals all have different levels of reactivity, and therefore, work better for certain environments.
Traditionally zinc has been the most popular metal to use as an anode. It is great for saltwater use but is ineffective at reducing corrosion in freshwater. When used in freshwater, zincs build up a coating that stops them from working. In high concentrations, zinc can be toxic to aquatic invertebrates, fish, and plants. Read More
How Many Zinc Anodes Do You Need?
The amount of sacrificial anodes you need depends on the metal surface areas of your boat. You will typically need roughly one percent of the metal surface area in anodes. Typically you don’t need to do these calculations, as most boat manufacturers will outfit their boat with anodes that will just simply need replacement.
If your anodes are not lasting around a year, you may want to consider adding more. The more anodes you have, the longer they will take to deteriorate. About a year is the minimum time they should last before requiring replacement.
Sacrificial Anode Locations and Shapes
Anodes come in different shapes and sizes for different purposes: Read More
Anodes come in different shapes and sizes for different purposes:
Motor Anodes
The smallest anodes, and arguably the most important, are in your motor. On inboard motors, they’re small cylinders placed in the heat exchanger. These small cylinders are referred to as pencil anodes. On outboard motors, they’re small cylinders that bolt into the cooling jacket of your outboard.
Propellers
Propeller anodes can be protected in multiple ways. On large vessels, this is with a propeller nut anode. On outboards, an anode washer can be used, or the anode on the lower unit can be sufficient. Anode specifications for outboards may vary by manufacturer.
Rudders
The rudder or rudders of large inboard boats or sailboats typically have small anodes that do not cause much drag or turbulence.
Propeller Shafts
Propeller shaft anodes go around the stainless steel shaft and bolt together on either side of the shaft. This design is intended to minimize drag and keep the shaft perfectly balanced. Selecting the perfect size is important as poorly sized anodes can cause balance issues and can result in poor corrosion protection.
Clip-on Anodes
Clip-on anodes can supplement a boat's existing anode system to counteract stray currents. They are not intended to replace any permanent anodes. They can be clipped to outdrives or other metal fixtures that need protection. Clip-on anodes can only be used while moored.
Hull Anodes
Hull anodes can be used to protect any electrically bonded accessories or to protect metal-hulled boats. These are typically much larger than other anodes.
Miscellaneous Anodes
Remember, anything below the waterline needs an anode or to be grounded to an anode! This includes trim tabs and through-hulls. Trim tabs have specifically designed anodes. Through-hulls can be electrically connected by wire to an anode.
Anode Troubleshooting
There are a few nuances to anodes. They must make electrical contact with the surface they are protecting. Anodes also should not be painted. Paint blocks the anodes from corroding. The surfaces that anodes are applied to also need to be paint-free surfaces. Paint can reduce electrical contact between the anode and the surface it is meant to protect. Read More
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