What is cathodic protection and how does it work?

Cathodic protection is a widely used technique in the field of corrosion prevention for metal surfaces, particularly in industries such as oil and gas, water and wastewater, and marine structures. In this blog post, we will explore what cathodic protection is and how it works to protect metal structures from corrosion.

What is cathodic protection?

Cathodic protection is a corrosion prevention technique used to protect metal structures from deteriorating due to contact with corrosion-causing agents like water, oxygen, and chemicals. It works by creating a negative voltage potential on the metal surface, effectively slowing down the corrosion process and extending the lifespan of the structure.

What is cathodic protection used for? 

Cathodic protection is important because it helps prevent costly repairs and replacements of metal structures, particularly in industries like oil and gas, water, and marine structures. It is commonly used for offshore oil platforms, pipelines, ship hulls, and underground tanks where metal structures are exposed to harsh environments. By implementing cathodic protection systems, industries can ensure the safety and longevity of their metal assets.

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Different types of cathodic protection

There are two main methods of cathodic protection: galvanic and impressed current.

In galvanic protection, a more reactive metal (Zinc and copper) is connected to the metal structure, creating a galvanic cell where the sacrificial anode corrodes instead of the protected metal.

In impressed current cathodic protection (ICCP), an external power source applies a direct current to the metal structure, causing the corrosion agents to be repelled.

The key difference between the two types lies in the source of the protective current: galvanic protection relies on the natural potential difference between metals, while impressed current protection requires an external power source to drive the protective current.

Pros and cons of galvanic anode cathodic protection.

Pros of galvanic anode cathodic protection include its simplicity, low maintenance requirements, and cost-effectiveness compared to impressed current systems. It is also suitable for smaller structures and remote locations where access to power sources may be limited.

However, there are some cons to consider. Galvanic anodes have a limited lifespan and may need to be replaced periodically. They also provide a fixed level of protection, which may not be sufficient for larger structures or environments with high corrosion rates.

Galvanic anode cathodic protection is best used in situations where a simple and cost-effective corrosion prevention method is needed, such as for smaller structures, remote locations, or where power sources are not readily available. It is a suitable choice when the level of protection provided by sacrificial anodes meets the requirements for the specific application.

Pros and cons of impressed current cathodic protection

Pros of impressed current cathodic protection include greater control and adjustability of the protective current, suitable for larger structures or areas with high corrosion risk., and longer-lasting protection compared to galvanic systems.

However, there are also some cons to consider. Higher initial installation and maintenance costs, requires regular monitoring and maintenance to ensure proper functioning, and potential for overprotection, which can lead to hydrogen embrittlement or other issues.

Impressed current cathodic protection is recommended when galvanic protection is not sufficient to provide the required level of corrosion prevention, especially in high-risk environments or critical infrastructure where precise control over the protective current is necessary. It is often used in industries such as oil and gas, marine, and transportation to protect vital structures from corrosion and extend their service life.