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Cathodic Protection

Cathodic Protection

Corrosion can cause significant damage and deterioration to pipelines and metal surfaces, leading to leaks, structural weakness, and reduced performance. To effectively combat corrosion and ensure the integrity of your equipment, cathodic protection is essential. Certified Material Testing Products offers a comprehensive range of cathodic protection coupons, enabling accurate evaluation and monitoring of corrosion levels.

Our selection of protection coupons includes various lengths, configurations, and types of metal, such as stainless steel, steel, iron, and aluminum. Whether you need coupons for testing purposes or as part of a corrosion solution, we have the right product for your specific application.

One of the featured products in this category is the M.C. Miller 146305 AccuRef 30 Copper/Copper Sulfate with Integrated Coupon. This high-quality product provides accurate and reliable measurements of corrosion potential and ensures the effectiveness of a current cathodic protection system.

If you require audible displays for monitoring corrosion rates, we offer the M.C. Miller SUB420 and SUB425 Audible Display models. These devices feature a beeper and counter to provide clear and concise feedback on corrosion levels, empowering you to take necessary measures promptly.

The cathodic protection system and coupons also come with twin THHN wires in various colors, including green, red, and yellow, allowing for easy identification and installation. With lengths ranging from 25ft to 100ft, you can choose the most suitable option based on your specific requirements.

For those requiring aluminum cylindrical coupons, our selection includes the popular M.C. Miller COU300 series. These coupons are equipped with twin THHN wires and are available in different lengths to accommodate your specific needs.

In addition, we offer carbon steel coupons with twin THHN wires, which are ideal for evaluating corrosion in pipelines and tanks. The M.C. Miller COU100 series is available in various lengths and features a green color for easy identification.

At Certified Material Testing Products, we understand the importance of protecting your valuable assets from corrosion. That's why we provide a wide range of a cathodic protection system and coupons and corrosion solutions to help you accurately assess corrosion levels and implement effective preventive measures. Browse our selection today and find the right products for your corrosion protection needs.

Cathodic protection (CP) is an electrochemical process used extensively to control corrosion on metal surfaces, particularly for buried or submerged structures like pipelines, tanks for storage, steel structures, and platforms offshore. This technique involves altering the electrical environment of the metal surface to be protected, making it the cathode of an electrochemical cell, which significantly slows down the corrosion rate.

There are two basic types of a cathodic protection system: galvanic cathodic protection and impressed current cathodic protection (ICCP). Galvanic systems, or sacrificial anode cathodic protection, utilize galvanic anodes made from more active metals such as zinc, magnesium, or aluminium. These anodes are electrically connected to the metal, and due to their higher reactivity, corrode instead of the protected structure. The sacrificial metal, acting as the anode, supplies additional electrons to the protected metal, effectively making it a cathode and preventing its corrosion.

Impressed current of a cathodic protection system protects through the use of an external power source, typically a protection rectifier, which drives a direct current (DC) through anodes made from materials like high silicon cast iron or mixed metal oxide. These impressed current anodes are buried around the structure to be protected and connected via cables. The external DC power source supplies enough current to overcome the electrical resistance of the soil or water, ensuring a uniform distribution of cathodic protection current across the entire surface of the metallic structure.

Both types of systems aim to achieve a potential difference between the anode and the metal to be protected, reducing the metal's corrosion rate to a negligible level. Effective cathodic protection is achieved when the protective current flows uniformly, allowing the entire surface of the structure to act as the cathode in the electrochemical cell.

Cathodic protection measurement techniques and criteria are critical for ensuring the system's effectiveness. Measurements typically involve reference electrodes to assess the potential difference and ensure it meets minimum federal safety standards for corrosion protection. The design and operation of CP systems consider factors such as soil resistivity, environmental conditions, and the presence of coatings on the metal surface, which can significantly affect the system's efficiency and the required current density.

Cathodic protection systems are designed to protect numerous structures in environments, from internal surfaces of structures to external surfaces of steel pipes and offshore oil platforms submerged in seawater. Besides preventing corrosion, cathodic protection also helps in preventing hydrogen embrittlement and maintaining the integrity of the structure over its intended lifetime.

For structures, CP can protect exposed steel reinforcements from corroding, extending the life of bridges, piers, and jetties. In marine environments, cathodic protection is essential for ships, offshore platforms, and submerged pipelines, protecting them from aggressive seawater corrosion.

Despite its advantages, cathodic protection requires regular monitoring and maintenance to ensure its long-term effectiveness. Systems may need adjustments in current output or anode replacements to maintain the protective criteria as different conditions change or as the structure ages. However, with minimal maintenance requirements and the ability to protect large structures in most environments, cathodic protection remains a cost-effective and widely adopted method for corrosion control in the construction and oil and gas industries, among others.

Even More of Information

Cathodic protection (CP) is a highly effective method used in corrosion engineering to safeguard metallic structures, particularly those buried or submerged, like pipelines, storage tanks, and reinforced concrete. It operates on the basic principles of electrochemistry, transforming the entire metal surface into a cathode within an electrochemical cell, thus preventing the electrochemical reactions that cause corrosion.


There are two main types of systems: galvanic (or sacrificial anode) cathodic protection and impressed current cathodic protection (ICCP).

Galvanic Anode

Utilizes galvanic or galvanic anodes made of a more active metal than the structure to be protected. These anodes, often made of zinc, magnesium, or aluminium, are electrically coupled to the structure. Over time, the sacrificial anodes corrode instead of the protected structure, supplying it with additional electrons to prevent its oxidation. This system is commonly referred to as passive cathodic protection due to its reliance on the natural potential difference between the sacrificial anode and the metal to drive the protective current flow.

Impressed Current

Involves an external power supply, such as a cathodic protection rectifier or solar panels, to provide a direct current (DC) to the metal structure via impressed current anodes, which are not consumed as rapidly as sacrificial anodes. These systems are designed to protect larger structures or those in highly corrosive environments by supplying a continuous flow of electrons from an external source to the metal structure, thereby ensuring its protection.

Design and Criteria

Designing a CP system requires a deep understanding of the corrosion engineering principles and the specific environments of the installation site. Cathodic protection design involves selecting the appropriate anode, calculating the required current density to protect the structure adequately, and determining the most effective configuration of anodes to ensure uniform protection.

Cathodic protection criteria have been established to ensure that sufficient protection is achieved. These criteria often involve measurements of the potential difference between the protected structure and a reference electrode placed in the same electrolyte, ensuring that the protected structure remains polarized in a negative direction to avoid corrosion.

Application and Monitoring

Cathodic protection systems protect numerous structures in various environments. They are particularly effective for steel pipes, offshore oil platforms, fuel pipelines, and structures exposed to aggressive environments. Regular monitoring and maintenance of systems are critical to their ongoing effectiveness, involving checks of anode life, current flow, and potential readings to ensure the system meets the protection criteria.

Environmental and Safety Considerations

While cathodic protection offers a robust solution to control corrosion, it also presents challenges, such as the potential for hydrogen embrittlement in some metals and the need for careful handling of anodic materials and power supplies. Furthermore, CP systems must be carefully designed and monitored to avoid stray current that can lead to accelerated corrosion of nearby metallic structures not intended to be protected by the system.


Cathodic protection represents a vital technology in the field of corrosion engineering, offering a proactive approach to extend the life of metallic structures and combat the costly and destructive effects of corrosion. Through the strategic application of galvanic or ICCP, combined with diligent monitoring and maintenance, cathodic protection continues to be a cornerstone in protecting vital infrastructure across a multitude of industries worldwide.

Even More Information on Cathodic Protection

Cathodic protection (CP) is a vital technique used in the mitigation of electrochemical of metallic structures, especially those buried or submerged in electrolytes such as soil, water, or concrete. This method involves altering the electrochemical environment of the metal to be protected, making it the cathode of an electrochemical cell. By doing so, CP effectively controls the corrosion rate of the metallic structure, extending its lifespan and ensuring the safety and integrity of infrastructure critical to modern life, from the oil pipeline to reinforced concrete structures.

Understanding Cathodic Protection

At its core, cathodic protection works by providing a more easily corroded sacrificial metal to act as the anode. The protected metal becomes the cathode, where the cathodic protection current flows, thereby preventing it from undergoing the electrochemical reactions that cause corrosion. This process is facilitated by an electrical circuit that connects the sacrificial anode to the metal needing protection, allowing electrons to flow from the anode to the cathode, thus neutralizing the corrosive effect of the electrolyte environment.

Types of Cathodic Protection

There are primarily two types of cathodic protection systems: galvanic (or sacrificial anode) systems and impressed current cathodic protection (ICCP) systems.

Galvanic Cathodic Protection Systems These systems utilize the galvanic cell principle, where two dissimilar metals are connected in an electrolyte. Zinc galvanic anodes are commonly used to protect steel structures buried in soil or submerged in water. The sacrificial anode, having a more negative electrode potential, corrodes in preference to the steel structure, thereby supplying it with electrons needed to remain protected. No external power source is required as the galvanic system is driven by the potential difference between the anode and the metallic structure.

Impressed Current Cathodic Protection (ICCP) Systems Unlike galvanic systems, ICCP use an external power supply to provide a constant protective current. These systems can protect larger structures and are not limited by the consumption rate of the anode. Anodes in ICCP can be made from various materials, including titanium coated with mixed metal oxides (MMO) and graphite. The power source, often a transformer rectifier, converts AC power to a direct current (DC), which is then supplied to the anode, ensuring that the CP current flows effectively to the structure leads.

Key Components and Principles

Anode Essential for both types of CP, anode materials vary from zinc and magnesium in galvanic systems to MMO and graphite in ICCP. The selection of anode material is crucial, as it impacts the efficiency and longevity of the cathodic protection work.

Protective Coating Although not a component of the CP itself, protective coatings are often used in conjunction with CP to minimize the current required to protect the underlying metal. Coatings act as a primary barrier against corrosion, while CP serves as a secondary protection method.

Power Supply In ICCP, the power supply is a fundamental component that converts AC power to the DC current necessary to drive the protection process. The supply electrons needed by the metallic structure to remain protected are crucial for the effectiveness of the system.

Electrochemical Corrosion Understanding the process of electrochemical corrosion is central to comprehending how cathodic protection works. Corrosion occurs when metal atoms lose electrons and become ions, which can then react with other elements to form corrosive products like rust. CP systems work by supplying electrons to the metal, thus preventing this loss and the subsequent corrosion process.

Applications and Considerations

Cathodic protection systems are used in a variety of applications, from protecting steel pipe used in natural and other gas transportation to safeguarding the hulls of boats and ships. Underground pipelines, oil pipelines, tank bottoms, and reinforced concrete structures are among the most common applications of CP. The effectiveness of a CP system in these various applications depends on several factors, including the soil resistivity, water chemistry, coating condition, and the presence of dissimilar metals that may cause stray current corrosion.

Challenges and Innovations

While cathodic protection offers a robust method for controlling corrosion, it is not without its challenges. The effectiveness of CP can be limited by factors such as incorrect system design, insufficient current supply, and coating damage. Additionally, monitoring and maintenance are critical to ensuring that CP continue to function correctly over time. Innovations in materials science, such as the development of more efficient anodes and improvements in coating technologies, continue to enhance the effectiveness and applicability of CP.


Cathodic protection is a proven and effective method for protecting metallic structures from corrosion. By understanding the principles of electrochemical and applying the appropriate type of CP, engineers can significantly extend the life of critical infrastructure, ensuring its safety and functionality. As technology advances, the efficiency and scope of cathodic protection systems are expected to improve, offering more sustainable solutions for

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