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A sacrificial anode is an anode that allows the circulation of current by its oxidation.

Sacrificial anode (partly corroded) intended to protect certain immersed metal parts of a boat hull

A metal more reducing than the metal to be protected will be used as an anode.

In the cathodic protection of steel or ferrous metals (e.g. on boat hulls and propeller shafts, galvanized steel swimming pools, etc.) by sacrificial anodes, zinc is often chosen for its electropositivity (Zn2+), its ease of molding and its good reactivity in an aggressive environment (chlorine)

Definition of the Sacrificial Anode

Sacrificial anodes, also known as galvanic anodes, are the protective mechanisms you must use against corrosion. While they do not completely stop corrosion, they do sacrifice to it.

How Sacrificial Anodes Work

The operation of a sacrificial anode is the same as that of an electrochemical cell.

Sacrificial anodes have a kind of protected metal on the cathode side. This is the negatively charged side of the device.

A more reactive metal or alloy is on the anode or positive side. It is important to note that the metal or alloy on the anode side must have a greater potential difference than the metal on the cathode side.

Once these two metals are in place, the reaction will occur spontaneously.

An oxidation reaction will occur at the anode. Oxidation means that the substance will lose electrons. Meanwhile, a reduction reaction will occur on the cathode side. This means that the substance will gain electrons.

The simultaneous production of oxidation and reduction reactions is known as a redox reaction. The oxidation on the anode side will ensure that this sacrificial metal corrodes. The reduction reaction at the cathode side will prevent the metal on that side from eroding.

What Materials Use Sacrificial Anodes

Sacrificial anodes have conductive wires that ensure they are connected to the structure they are protecting. If there are lead wires in place, they can be attached by welding or mechanical connections.

Without these wires, the sacrificial anode cannot absorb corrosion from the protected metal.

As for metals, sacrificial anodes usually use relatively pure active metals such as zinc or magnesium. Alternatively, they could use magnesium or aluminum alloys that scientists have composed specifically for the purpose of becoming a sacrificial anode.

Advantages of using Sacrificial Anodes

Sacrificial anodes have many advantages. After all, they completely change the way corrosion works and protect important materials.

First, sacrificial anodes do not require the use of energy. Therefore, they are useful wherever they are needed.

Second, sacrificial anodes are a relatively inexpensive solution to corrosion. Compared to more advanced techniques, sacrificial anodes are less expensive while still being protective.

Sacrificial anodes also do not require supervision. Chemical reactions do occur, but they are not dangerous or toxic. Therefore, you can leave the sacrificial anode connected to the metal it protects.

These devices are also easy to install. All you have to do is make sure it is securely attached to the metal it is protecting.

From there, you can let the sacrificial anode conduct its redox reaction and produce corrosion on the sacrificial metal rather than the protected metal.

Finally, sacrificial anodes are easy to add. A sacrificial anode cannot protect a vessel by itself. However, you can add as many of them as you need.

Again, they are a cheaper option that is easy to install. So, you just have to figure out what the right amount is for your project.


The chemical reactions that occur inside the sacrificial anode cannot last forever. Therefore, you will need to check the anode periodically so that you can detect when it is time to change the existing system for a new one.

You will know it is time for a new sacrificial anode when the anode is completely consumed by corrosion.

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