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Points to take into account in the Cathodic Protection of structures in marine and deep water environments

Inspenet, October 18, 2023. Structures such as oil platforms, underwater pipelines and docks are constantly exposed to corrosive environments. The salinity of seawater, marine life, among others, contribute to speeding up this process. Therefore, it is imperative to take preventive measures. In this article, some considerations in the cathodic protection of these structures are presented.

Antonio Zavarce.

Published: October 18, 2023

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Author: Ing. Antonio Zavarce, October 18, 2023.

Introduction

Cathodic Protection (CP) is an essential technique to ensure the integrity and durability of marine and deepwater structures. These structures, such as oil platforms, underwater pipelines and docks, are constantly exposed to corrosive environments. Seawater salinity, pressure, currents and marine life all contribute to accelerating the corrosion process. Therefore, it is imperative to take preventive measures. In this article, some considerations in the cathodic protection of these structures are presented.

Marine corrosion

Corrosion is an electrochemical reaction that occurs when a metal oxidizes. In the marine environment, salt acts as an electrolyte, facilitating the flow of current between anodic areas (where corrosion occurs) and cathodic areas (protected against corrosion). Structures submerged in deep water face additional challenges due to high pressures and low temperatures.

What is cathodic protection?

PC is a technique that converts the entire metal surface of a structure into a cathode, making it immune to corrosion. This is achieved through two main methods:

Sacrificial anodes: These are more reactive metals (such as zinc or aluminum) that corrode rather than the metal they are intended to protect. They “sacrifice” themselves to protect the main structure.
Impressed current cathodic protection (PCCI): Uses an external power source to apply an electrical current that protects the structure.

Modern considerations for PC in marine structures

Method Selection: While sacrificial anodes are ideal for smaller structures due to their simplicity, PCCI is more suitable for large, complex structures due to its efficiency and ability to cover large areas.
Monitoring and control: With current technology, it is possible to monitor the status of cathodic protection in real time. Sensors and remote monitoring systems allow the protection current to be adjusted as necessary.
Advanced Materials: New sacrificial anodes made from specialized alloys offer greater efficiency and durability. Additionally, recent research suggests that conductive coatings can improve PC effectiveness.
Environmental impact: It is essential to select anodes and systems that are ecologically sustainable and that do not release toxic substances into the environment.

Deep water challenges

Deepwater structures, such as oil and gas pipelines, face extreme conditions. High pressure and low temperatures can affect the effectiveness of the PC. Additionally, the logistics of installing and maintaining these systems at these depths are challenging. Recent innovations in underwater robotics and remotely operated vehicles (ROVs) are making these tasks easier.

What are the problems that have motivated the considerations presented?

The problems in the subject of cathodic protection of marine and deep water structures have evolved over time, and it has been precisely these issues that have led to considerations and advances in the matter. Below are some of the main problems:

1. Structural failures due to corrosion: Untreated corrosion has led to catastrophic failures in marine structures, resulting in significant economic losses and, in some cases, environmental and human disasters.

2. Inefficiency of old systems: The first cathodic protection systems, although effective at the time, were not as efficient as modern solutions. This resulted in incomplete protection and the need for frequent maintenance.

3. Deepwater Logistics Challenges: Deepwater structures, such as subsea pipelines, present unique challenges due to pressure, temperature, and accessibility. These factors complicated the installation and monitoring of cathodic protection systems.

4. Environmental impact: Older systems, especially sacrificial anodes, could release metals and other compounds into the marine environment, raising ecological concerns.

5. Associated costs: Installation, maintenance and replacement of cathodic protection systems in marine and deepwater structures can be expensive. The search for more durable and efficient solutions has been driven, in part, by the need to reduce these costs in the long term.

6. Technological advances: With the development of technology, new challenges arose, such as the need to protect electronic equipment and submerged sensors, which may be sensitive to electrical currents.

7. Changes in regulations: International regulations and standards regarding the safety and security of marine structures have become stricter, driving the need for more effective cathodic protection systems.

These problems have led the industry and the scientific community to research and develop more advanced and efficient solutions. Modern considerations in cathodic protection are a direct result of facing and overcoming these challenges over the years.

conclusion

Cathodic protection is essential to guarantee the useful life and safety of marine structures in deep waters. As we move into the 21st century, the combination of traditional and modern technologies, together with a deep understanding of marine corrosion, will allow us to better protect our valuable infrastructure against the rigors of the marine environment. It is essential to stay up to date and adopt the latest techniques and materials to ensure optimal protection.