What does the term "sacrificing metal" refer to in cathodic protection systems?

The term "sacrificing metal" in cathodic protection systems refers to a specific type of metal that is intentionally corroded to protect other, more critical metal structures from corrosion. In cathodic protection, a more anodic metal is used as a sacrificial anode. When this metal is placed in proximity to a structure that needs to be protected—such as steel pipelines, storage tanks, or other underground metal structures—it will corrode instead of the protected metal. This process occurs because the more reactive (anodic) metal will preferentially oxidize, effectively redirecting the corrosive reactions away from the structures which need to be safeguarded.

In cathodic protection systems, these anodes can be made from various materials, such as zinc, magnesium, or aluminum, each chosen based on the conditions of the environment they are used in. The sacrificial anode system is critical for prolonging the lifespan of metal structures exposed to harsh conditions, such as marine environments, where corrosion risks are heightened.

Understanding this concept is essential for engineers working in water resources and environmental engineering since it represents a practical application of electrochemical principles to protect infrastructure and ensure its durability against corrosion.