Sacrificial Anode Cathodic Protection: An Effective Solution Against Corrosion in Buried Pipelines

 Buried pipelines play a critical role in transporting water, oil, gas, and chemicals across long distances. However, being in constant contact with soil and moisture makes them highly vulnerable to corrosion. Understanding what is corrosion and how specific forms like galvanic corrosion affect underground metal structures is essential for ensuring pipeline safety and longevity. One of the most reliable methods to prevent corrosion damage in buried pipelines is sacrificial anode cathodic protection.

 What Is Corrosion and Why It Occurs in Buried Pipelines

To understand pipeline protection, it is important to first answer the question: what is corrosion? Corrosion is a natural electrochemical process in which metals deteriorate due to reactions with their environment, particularly oxygen, moisture, and electrolytes present in soil.

In buried pipelines, corrosion occurs because:

• Soil contains moisture and dissolved salts that act as electrolytes
• Differences in soil composition create electrical potential variations
• Coating defects expose bare metal to corrosive conditions

Over time, this leads to metal loss, leaks, reduced pressure capacity, and even catastrophic pipeline failures.

 Understanding Galvanic Corrosion in Underground Pipelines

Galvanic corrosion is a specific type of corrosion that occurs when two dissimilar metals are electrically connected in the presence of an electrolyte, such as moist soil. In this scenario, the more active (less noble) metal corrodes faster, while the more noble metal is protected.

In pipeline systems, galvanic corrosion can occur due to:

• Contact between pipeline steel and different metals
• Weld joints or fittings made from dissimilar materials

Repairs using incompatible metal componentsIf not controlled, galvanic corrosion can significantly shorten the service life of buried pipelines.

 Principle of Sacrificial Anode Cathodic Protection

Sacrificial anode cathodic protection works by deliberately attaching a more active metal (anode) to the pipeline. This anode corrodes instead of the pipeline, thereby protecting the main structure.

Common sacrificial anode materials include:

• Magnesium
• Zinc
• Aluminum alloys
• These materials have a higher tendency to corrode than steel. When connected to the pipeline, the sacrificial anode becomes the anode in the electrochemical cell, and the pipeline becomes the cathode—preventing corrosion of the pipeline metal.

 How Sacrificial Anode Cathodic Protection Prevents Corrosion

The system functions by supplying a continuous flow of electrons from the sacrificial anode to the pipeline surface. This process:

• Reduces metal loss from the pipeline
• Neutralizes corrosion reactions
• Protects exposed steel at coating defects

By addressing what is corrosion at its electrochemical root, sacrificial anode cathodic protection offers a long-term and reliable solution for buried pipelines.