FAQ: How does a sacrificial anode work

A sacrificial anode system is a form of protecting submerged structures from CORROSION by using sacrificial anodes, also known as galvanic anodes, which are the basis of traditional galvanic cathodic protection systems.

To understand how does a sacrificial anode work, it’s essential to delve into the basics of galvanic corrosion. When two different metals are in electrical contact and exposed to an electrolyte, such as seawater, a galvanic cell is formed. The more reactive metal (the anode) will corrode preferentially, protecting the less reactive metal (the cathode). In this context, the sacrificial anode, typically made from zinc, aluminum, or magnesium, acts as the anode, corroding over time to save the primary metal structure.

So, how does a sacrificial anode prevent corrosion in marine environments? The sacrificial anode method ensures that the anode material degrades instead of the protected structure. This continuous degradation process of the sacrificial anode keeps the protected metal safe from the aggressive corrosive elements present in seawater. By understanding how does a sacrificial anode work, industries can better protect their valuable assets.

The sacrificial anode method of cathodic protection is easy to install and requires little expertise. As they require no external power source, sacrificial anodes they are particularly suitable for smaller structures or those is simple and has been used for hundreds of years.

The sacrificial anode method of cathodic protection presents several problems owing to how sacrificial anodes work. Over the lifetime of every anode, large quantities of zinc, magnesium or aluminum are released into the water, together with heavy metals such as cadmium.

Moreover, a sacrificial anode system does not offer the same level precision as modern cathodic protections such as ICCP systems. There is, for instance, no means to check the efficacy of the protection offered by the sacrificial anode method over time without employing divers to conduct an underwater inspection.

Sacrificial anode protection methods also have a finite life. This means that they always need to be replaced, which adds to there already significant carbon footprint.

In marine environments, sacrificial anodes are often attached to the hulls of ships and boats. How does a sacrificial anode prevent corrosion in this context? By corroding first, the anodes protect the vessel’s hull from the detrimental effects of saltwater, extending the lifespan of the ship and reducing maintenance costs. Basically, it sacrifices itself to protect another metal, like the hull, ruder and propellor.

The answer lies in the anode’s ability to corrode first, thus safeguarding the vessel’s hull from the detrimental effects of saltwater. This process extends the lifespan of the ship and significantly reduces maintenance costs.

Offshore wind turbine foundations, like monopile, jackets and suction buckets are other critical areas where sacrificial anode cathodic protection is employed. These structures are constantly exposed to harsh seawater conditions, which can lead to rapid corrosion. The sacrificial anode protection method helps prevent this, ensuring the structural integrity and safety of these installations

In the world of corrosion prevention, the galvanic series plays a crucial role, especially in the application of cathodic protection. But how sacrificial anode works and understanding this series is key to effectively safeguarding metal structures from corrosion, particularly in marine and offshore environments. The Galvanic series shows the natural potentials of material which is mandatory to know to choose your sacrificial anodes.

The galvanic series is a list that ranks metals and alloys based on their electrochemical activity in a specific environment, typically in 100% seawater measured with Ag/AgCI reference cell. This ranking helps in determining how metals will react when they are in electrical contact with each other. Metals higher in the series are more anodic and are more likely to corrode, while those lower in the series are more cathodic and less likely to corrode.

The galvanic series is fundamental in cathodic protection because it helps in selecting appropriate sacrificial anodes. But what is sacrificial anode cathodic protection? Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. This is achieved by attaching a more anodic metal (sacrificial anode) to the metal that needs protection. The sacrificial anode will corrode instead of the protected metal.

To understand how the galvanic series works, consider the interaction between different metals when they are submerged in an electrolyte, such as seawater. Metals higher in the galvanic series, like zinc, aluminum, and magnesium, are more reactive and will corrode preferentially when in contact with metals lower in the series, such as steel or copper. This principle is the basis for sacrificial anode cathodic protection.

In marine environments, the galvanic series is particularly useful for protecting ship hulls, offshore platforms, and wind turbine foundations. By selecting sacrificial anodes from higher in the series, such as zinc or aluminum, these structures can be effectively protected from the corrosive effects of seawater. The sacrificial anodes corrode over time, thus preventing the more valuable metal structures from degrading.

When implementing cathodic protection, it is essential to choose the right sacrificial anode. The galvanic series provides a guideline for this selection. For example:

Zinc Anodes: Commonly used in seawater environments for protecting steel structures.

Aluminum Anodes: Often used for offshore (wind) structures due to their high efficiency and capacity.

Magnesium Anodes: Suitable for freshwater environments and highly resistant structures.

By understanding the position of these metals in the galvanic series, engineers can ensure optimal protection for their structures.

Understanding the galvanic series is essential for effective corrosion prevention through cathodic protection. It helps in predicting the behavior of different metals in contact and in selecting the appropriate sacrificial anodes. This knowledge is crucial for maintaining the integrity and longevity of metal structures in harsh environments.

Corrosion is a significant challenge in marine and offshore environments, where structures are constantly exposed to harsh conditions. One of the most effective ways to combat this issue is through the use of sacrificial anodes. But how does sacrificial anodes prevent corrosion? The answer lies in the principles of electrochemistry.

Sacrificial anode protection, also known as sacrificial anode cathodic protection or SA, is a method used to protect metal structures from corrosion. This technique involves attaching a more reactive metal, known as the sacrificial anode, to the structure needing protection. The sacrificial anode corrodes in place of the protected metal, hence the term “sacrificial.”

For the sacrificial anode protection method to be effective, regular inspection and maintenance are essential. Over time, the anodes will corrode and need replacement. Understanding what is sacrificial anode protection and how it works helps operators schedule timely replacements, ensuring continuous protection and minimizing the risk of unexpected failures. CORROSION service engineers can assist with CP measurements and support.

In summary, the use of sacrificial anodes in marine and offshore environments is a proven technique to safeguard metal structures from corrosion. By understanding what sacrificial anode protection is and how  sacrificial anode works, industries can effectively extend the lifespan of their assets and ensure operational safety in corrosive environments. This knowledge is crucial for maintaining the integrity of structures in some of the most challenging environments on Earth.

CORROSION has a standard stock of Sacrificial anodes to supply complementary with an active protection system, an ICCP system. This way, vessels are protected in areas that receive insufficient protection by applying an ICCP system.

In cooperation with our partner Metec, based in England, Italy and Tunisia, we support Offshore Wind Farm owners with high-quality sacrificial anodes.

Contact the service or sales department for information and orders.