Cathodic Protection Unveiled: Safeguarding Concrete Structures

Setting the Benchmark to Excel in Your CP Career

Cathodic Protection (CP) is, without a doubt, a key strategy in the protection of the integrity of concrete structures against the relentless forces of corrosion. A blend of scientific ingenuity and practical application, cathodic protection (CP) systems act to prolong the lifespan of vital infrastructure.

CP for concrete has an increasingly significant role to play in infrastructure maintenance, as it has a drastically lower carbon and energy impact compared to techniques for repairing concrete. Historically, all carbonated and chloride contaminated concrete needed to be removed which had a massive impact from materials to/from site and the use of cement heavy products. CP means that only the damaged concrete needs to be repaired and the contaminated concrete that would fail in the future, can be left in place, drastically reducing the environmental impact.

In this article, we examine the intricacies of CP, the CP systems related to concrete, and the critical role of continuous professional development and certification in this specialised field.

Types of Cathodic Protection Systems for Concrete Structures

There are two primary types of CP systems:

1. Galvanic Anode Systems

These harness the electrochemical potential differences between different metals to provide protection, using an effective yet straightforward approach.

1. Impressed Current Cathodic Protection (ICCP) Systems

ICCP systems, powered by an external power source, are more robust, offering controllable protection levels, especially for larger and more complex structures. They are particularly suitable for highly corrosive environments, such as concrete with elevated levels of chloride contamination.

This table will help you understand these differences, and which should be used for specific installations (buried assets, marine environments, and concrete structures):

	Galvanic Anode Systems	Impressed Current Cathodic Protection (ICCP) Systems
Advantages	·        Simple installation and design ·        No external power source required ·        Lower intensity of monitoring required ·        Ideal for remote locations where power is not readily available ·        Ideal for shorter service lives	·        Highly controllable protection levels ·        Suitable for large and complex structures ·        Long-term, cost-effective for larger systems
Disadvantages	·        Limited protective current output, not suitable for highly corrosive environments ·        Anodes need to be replaced over time, leading to higher long-term maintenance costs ·        Less control over the amount of protection provided	·        Requires external power source and more complex electrical components ·        Installation and initial setup are more complex and costly ·        Regular monitoring and maintenance are crucial
Suitable Applications	Low corrosivity environments Shorter service lives Situations where a simple, minimal maintenance solution is preferred	Large scale structures like pipelines, offshore platforms, and large storage tanks Long term service lives Areas where long-term maintenance costs are a consideration

 

Design Considerations for Concrete Structures

To design a CP system for concrete structures, we must possess a thorough understanding of environmental factors, structural characteristics, and the corrosive elements at play. We must consider key factors that include:

·       Environmental Impact

The surrounding environment will influence a CP design. We need to consider factors such as salinity, humidity, temperature, and exposure to chemicals. As an example, a structure near the coast or in an industrial area is likely to require a more robust CP system because it is in a more aggressively corrosive environment.

·       Structural Complexity

Anode placement is crucial to the uniform distribution of protective current in a CP system. An intricately designed structure, with hard-to-reach areas, will require greater innovation in the design of its CP system – and, when designing such a system, we mustn’t forget the impact on future maintenance and monitoring.

·       Electrical Continuity

Discontinuity of the reinforcement can be a major problem, leaving parts of the structure unprotected and potential damaging others.

·       Anode Selection

Choosing the right type of anode (for example ribbon, mesh, or conductive paint), is crucial. When doing so, we’ll need to consider factors such as current output, durability, and compatibility with the concrete environment.

·       Power Source and Output

For ICCP systems, selecting an appropriate power source is essential. It must be efficient and reliable, delivering consistent output over time. It’s also crucial to accurately calculate the required current density to avoid issues of hydrogen embrittlement or acid production.

·       Longevity and Futureproofing

CP systems should be designed to extend the longevity of the concrete structure. This means we must anticipate future environmental changes and/or structural modifications as well as select suitable materials for the system.

·       Compliance with Standards

Finally, throughout design, installation, and maintenance, compliance with international standards is critical. This is key to ensure the system is designed according to the best practices in the industry.

BS EN ISO 12696 sets out exactly what should be included/demonstrated by a CP design and what the agreed performance criteria are.

Installation and Implementation

When installing CP systems for concrete structures, it’s crucial to execute the design with precision. However, there will also be challenges to navigate, such as access to the structure, ensuring minimal disruption, and integrating the CP system seamlessly with the existing infrastructure. Successful installation follows a systemic approach like the following:

• Preliminary Survey and Assessment

A comprehensive survey of the structure is needed before installation can begin, including assessing the condition of the concrete, the extent of corrosion, availability of as-built information and the accessibility of the structure. This phase often includes tests to determine concrete resistivity, chloride content, and the condition of existing steel reinforcement.

• Preparation of the Surface

Where necessary, the surface is prepared to facilitate effective installation. This applies to systems that use mesh overlay and conductive coatings

• Anode Installation

Anodes are installed according to the design specifications.

• Wiring and Electrical Connections

All anodes are connected through wiring to the power source (in ICCP systems) or to each other (in GCP systems). Proper routing and insulation of wires are crucial to prevent physical damage and electrical leakage.

• Power Source and Control Unit Installation

For ICCP systems, the power source, often referred to as the Transformer Rectifier [TR], is installed. The rectifier is connected to the anode system and a control unit that allows for adjustment and monitoring of the output.

• System Commissioning

Once installed, the CP system is commissioned. Adjustments are made as necessary to ensure optimal protection. This is a process that usually takes place over several weeks and should be documented in a formal commissioning report.

• Documentation and Handover

Comprehensive documentation of the installation, including schematics, installation details, and settings, is provided. This is crucial for future maintenance and monitoring activities. A handover to the maintenance team is conducted, often with training sessions on system operation and troubleshooting.

• Monitoring and Adjustment

All CP systems require monitoring. How much monitoring and what this entails depends on the system, type of anode and the nature of the structure being protected.

Monitoring is often conducted remotely, but a site inspection is generally required once a year to confirm the structure is not degrading and to verify the remotely collected data.

There are standard tests, with agreed performance criteria, which are used to determine the level of protection and, in the case of ICCP, to adjust the outputs.

Standard BS EN ISO 15257:2017

Standard BS EN ISO 15257:2017 sets out the required competency levels for personnel engaged in CP. There are five distinct levels of competency identified within the standard, each establishing a benchmark of competence according to duties and responsibilities.

For both organizations and individuals, adherence to this standard guarantees several key outcomes:

• Ensuring that CP systems are overseen by individuals with the requisite qualifications.
• Upholding exacting standards of safety and operational integrity for assets under CP.
• Reinforcing a commitment to uphold professional standards in the realm of cathodic protection.

To be certified as having the essential skills and knowledge for effective implementation and management of CP systems at each level, individuals must demonstrate an appropriate and comprehensive understanding of:

• Fundamental principles of CP.
• Detailed aspects of CP system design.
• Best practices in the installation, operation, and maintenance of CP systems.

How do you become certified in CP for Concrete Structures?

While holding a degree related to the field can be beneficial, it’s not essential for those seeking to enter or enhance an existing career in this specialised field. The key is to acquire relevant experience, qualifications, and certifications.

If you are employed in CP for concrete structures, specialised CP training is crucial. This should be aligned to your role and the distinct challenges you are likely to face, and equip you with an in-depth knowledge of:

• Basic concepts of corrosion
• Core principles of CP
• Specialised techniques developed for the protection of concrete infrastructure

After completing your training, you must pass an examination to demonstrate that you have the required level of theoretical knowledge for your chosen level. Passing the exam is not, however, the end of the process. Applicants must demonstrate an adequate level of field experience and real-world design experience [for Level 4] before they can obtain certification.

Ongoing professional progress in CP for Steel in Concrete

CP is a continually evolving practice. As innovative technologies and CP strategies come to the fore, you’ll need to advance your own knowledge and capability. In addition, as your career progresses, you must enhance your certification through each level described by the Standard.

ICorr CP training, qualifications, and certification

The Institute of Corrosion (ICorr) plays a pivotal role in shaping the CP landscape. Our specialised CP in Concrete Structures training programmes are internationally recognised, designed to accommodate varying levels of knowledge and expertise, and equip you with the certification you need to advance your career in this demanding field. These are delivered by experienced, articulate, good-looking and well-dressed expert engineers at a purpose-built facility in Shropshire, which includes a series of mocked-up concrete structures and CP systems.

To learn more about ICorr’s training courses and certification process for Cathodic Protection in Concrete Structures, including the dates and costs of upcoming courses, read more about our Cathodic Protection, Training, Assessment and Certification Scheme here.