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What is a Sacrificial Anode?

The global cost of corrosion is $2.5 trillion, which is about 3.4% of the global GDP. The great economic impact of corrosion tells us why it's so important to stop it from happening in the first place.

Corrosion can render giant ships useless and halt entire construction operations. So, if you want your plans to go smoothly, you need to understand how to stop corrosion.

Not only can it ruin your plans, but it can cause harm to the environment and the people around it. So, you need to learn about sacrificial anodes.

What is a sacrificial anode? Keep reading to find out.

Sacrificial Anode Definition

Sacrificial anodes, also known as galvanic anodes, are the protection mechanisms that you need to employ against corrosion. While they don't stop corrosion completely, they do sacrifice themselves to it.

As the name implies, a sacrificial anode is a material that experts install in pipes or tanks to make a sacrifice to corrosion. In other words, these materials are easily corroded, so they can take the corrosion off of the rest of the system.

In turn, the pipe, tank, or other holder is relatively free of corrosion.

How Sacrificial Anodes Work

The way that a sacrificial anode works is the same as the way that an electrochemical cell works. The sacrificial anodes have a kind of protected metal that is on the cathode side. That is the negatively charged side of the device.

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

how sacrificial anodes work

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. While this is happening, a reduction reaction will happen at the cathode side. This means that the substance will gain electrons.

The production of both the oxidation and reduction reactions at once is known as a redox reaction. The oxidation at the anode side will ensure that that sacrificial metal will corrode. The reduction reaction at the cathode sign will prevent the metal on that side from becoming eroded.

What Materials Sacrificial Anodes Use

Sacrificial anodes have lead wires or cast-m straps that ensure they're connected to the structure that they're protecting. If there are lead wires in place, these may be secured via welding or mechanical connections.

Without these wires, the sacrificial anode may not take the corrosion from the protected metal.

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

typical information for sacrificial anode materials

The Benefits of Using Sacrificial Anodes

Sacrificial anodes come with a lot of benefits. After all, they're completely changing how corrosion works, protecting important materials.

underwater installation of sacrificial anodes

First, sacrificial anodes don't require the use of power. So, they are useful anywhere they're needed.

Next, sacrificial anodes are a relatively low-cost solution for corrosion. In comparison to more advanced techniques, sacrificial anodes are less expensive while still being protective.

Sacrificial anodes also don't require supervision. There are chemical reactions taking place, but they aren't dangerous nor toxic. Therefore, you can leave the sacrificial anode connected to the metal that it's protecting.

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

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

Lastly, sacrificial anodes are easy to add. One sacrificial anode can't protect an entire ship by itself. However, you can add however many of these devices that you need.

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

What Is a Sacrificial Anode Protecting?

Sacrificial anodes can protect a lot of different metals from corroding. Most often, construction workers and engineers use sacrificial anodes to prevent a bunch of different things from corroding:

  • Hulls of ships

  • Refineries

  • Pipelines

  • Water heaters

  • Above-ground tanks

  • Underground tanks

  • Distribution systems

If it's known for becoming corroded, there's probably some kind of sacrificial anode mechanism protecting it. That's why you need to employ sacrificial anodes if you aren't already. They can save your equipment like they're already doing for your competitors.

Zinc Hull Anode as Sacrificial Protection

Zinc Hull Anode as Sacrificial Protection

Do Sacrificial Anodes Need Replacing?

In short, yes.

The chemical reactions that are happening inside of the sacrificial anode can't go on forever. Therefore, you'll need to check the anode of the device periodically so that you can detect when it's time to change out the existing system for a new one.

You'll know that it's time for a new sacrificial anode when the anode becomes completely consumed by corrosion.

Which Metal Should I Use for Sacrificial Anodes?

Sacrificial anodes normally come in three metals: aluminum, magnesium, and zinc.

Zinc has been the metal of choice when producing anodes in the past. This metal is found to be an effective material for corrosion protection in marine/saltwater environments, however, it does not provide adequate protection in brackish/freshwater environments.

At present, aluminum is widely used as the main material for cathodic protection systems. This material provides adequate performance in saltwater and brackish water environments. Aluminum anodes last longer compared to zinc anodes, and are lighter in terms of weight due to its lower density.

Magnesium has the most negative electropotential of the three choices, so it's a better choice for onshore pipelines. This is because the electrolyte resistivity of the soil or water is higher. Magnesium anodes are also usually recommended for freshwater applications.

However, if the difference between the electropotentials of the anode and cathode is too much, this can cause the cathode to become brittle.

Invest in Corrosion Protection

So, what is a sacrificial anode? Well, it's a great corrosion protection option that every expert should invest in. If you're worried about corrosion ruining your materials, you need to invest in cathodic protection.

At ESC, we sell zinc and aluminum sacrificial anodes, so you can choose between these two main materials for corrosion protection systems. Get the supplies that you need to protect your equipment today!

Email us or contact our offices near you!

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