Introducing Cathodic Protection – How Does Cathodic Protection Work?

Introducing Cathodic Protection – How Does Cathodic Protection Work?

Blogs, Cathodic Protection Blog

Cathodic protection methods – differences and similarities

In our last article, we examined electrochemical corrosion and introduced the major areas where cathodic protection is used to protect against corrosion in aggressive environments such as soils, waters, and chloride contaminated concrete.

In this article, we take a deeper dive into how cathodic protection works.

The two types of cathodic protection

There are two types of cathodic protection: galvanic anode and impressed current cathodic protection.

Both provide a cathodic protection current flow from cathodic protection anodes placed within the same electrolyte as the metal to be protected. The current flows from the anode into the electrolyte. It discharges onto the metal, controlling the corrosion. It must flow within the metallic circuit (the metal plus the cables) and back to the anode to complete the circuit.

Galvanic anode cathodic protection (GACP)

Galvanic anode cathodic protection works as summarised above.

The anode materials are alloys of either zinc, aluminium, or magnesium – all more active metals than, for example, carbon steel. These more active metals corrode preferentially to the steel when they are metallically connected to the steel in an electrolyte.

The corrosion current of the anode material is the cathodic protection current for the steel. The current flows through the electrolyte onto the steel, controlling its corrosion. The current returns to the anode in the metallic circuit.

You may have heard the term ‘sacrificial anodes’. However, though this terminology describes the anode materials and how they act (the galvanic anode corrodes preferentially to the steel), it was changed in Europe in the 1980s to ‘galvanic anodes’.

You may see galvanic anode cathodic protection identified by the acronym SACP or GACP.

·         How is galvanic anode cathodic protection used?

Offshore, anodes are normally cast onto structural tubular cores which are welded to the offshore structure during construction onshore.

Offshore oil and gas pipelines are protected with aluminium alloy or zinc bracelet anodes clamped over the protective coating and connected to the pipeline by short cables or welded connections. Such protection should last for 30 years or longer.

Onshore, short pipelines are often protected using magnesium anodes. These are cast onto steel cores and connected to the pipeline with cables. In soils of low electrical resistivity, extruded or continuously cast and hot-rolled zinc ribbon is used. Zinc ribbon is widely used as an earthing electrode to mitigate induced alternating current (AC) on buried pipelines.

Impressed current cathodic protection (ICCP)

Impressed current cathodic protection is provided by connecting a DC power source between the metal being protected and the cathodic protection anodes. In contrast to GACP, the cathodic protection current is supplied by the DC power source and not by corrosion of the anode itself.

The DC power supplies are typically transformer rectifiers (confusing acronyms include TR, TRU and T/R) which convert mains electricity to low voltage DC. In remote areas, solar panels and batteries are commonly used (and stolen); thermo-electric DC generators and both diesel and gas engines driving generators have also been used.

The negative pole is connected to the protected metal (‘negative drain point’), and the positive pole is connected to the anode. As with GACP, the cathodic protection current flows from the anode, through the electrolyte and onto the metal being protected.

The anodes can be scrap steel (a reasonably common practice in France, where old railway rails are often used in such applications), high silicon iron, or sophisticated ‘mixed metal oxides’ coated onto titanium. Other materials, including graphite, magnetite, lead, platinum-coated titanium and niobium, have also been used, though performance and cost have combined to reduce their use.

·         How is impressed current cathodic protection used?

Offshore, anodes are typically mixed metal oxide coated titanium (MMO/Ti). These can be used in both seawater and saline mud, though in the latter their consumption rate is greater.

For steel in concrete, most impressed current systems use MMO/Ti anodes either in mesh, strip, or tubular form. There is a tubular anode formed into a conductive ceramic of MMOs.

In onshore applications, groups of anodes are normally used in ‘groundbeds’, which may take the form of a long horizontal trench in which multiple anodes are buried in a carbonaceous backfill. This increases the surface area, reduces the electrical resistance to ground, and extends the anode life. Similarly, anodes and ‘coke’ can be used in deep boreholes or multiple shorter boreholes. Anodes are typically high silicon cast iron or MMO/Ti.

Most impressed current systems will require replacement after about 25 years.

Which form of cathodic protection is best?

If the cathodic protection system is well designed, installed, operated and maintained, both galvanic anode and impressed current cathodic protection can be equally effective. However, GACP is simpler and has proved to be more reliable offshore.

Onshore, ICCP systems are easier to access for maintenance and, once installed, their components are not subject to the challenges of offshore environments. If properly designed, ICCP can protect many kilometres of well-coated pipelines.

ICCP is also advantageous for bare or poorly coated steel as it can deliver hundreds of amps of low voltage direct current, while a typical galvanic anode will seldom deliver more than 5 amps.

Cathodic protection – a specialist operation

Cathodic protection is used extensively to protect critical infrastructure from corrosion. For example:

  • It is legally mandated for gas and oil pipelines to ensure their safe operation
  • Offshore gas and renewable energy structures are effectively mandated to receive effective cathodic protection by their certification bodies
  • Ships benefit from extended dry-docking rules if they have effective cathodic protection
  • The life of concrete bridges and structures affected by chlorides, from de-icing salts or marine exposure, is extended by cathodic protection
  • Newly constructed, reinforced concrete structures in severe exposure conditions also have extended life when cathodic protection is used

However, across all functions – from design through installation to testing and maintenance – cathodic protection is highly specialised. There are standards (BS ENs and BS EN ISOs) for cathodic protection applications for different structures in different environments.

A key takeaway from the standards is that they make it clear that cathodic design must be undertaken by cathodic specialists with a documented, appropriate level of competence.

How do you gain a cathodic protection specialisation?

There are no degrees that can be gained in cathodic protection, and there are no postgraduate courses in cathodic protection engineering, either. Instead, you find that cathodic protection specialists may hold a science or engineering degree (or complete an apprenticeship) before undertaking specific training and gaining experience and expertise in cathodic protection.

The Institute of Corrosion offers courses in cathodic protection, providing the training required for levels 1 to 3 for cathodic protection data collectors, technicians and senior technicians. These courses are produced, owned and administered by the Institute of Corrosion CP Governing Board (CPGB).

These courses are designed for those seeking the certification of competence in accordance with standard BS EN ISO 15257. We also find that these courses add value to managers and others who want to know what their cathodic protection staff and/or contractors must be doing and the limits of what they should do.

Independent of the cathodic protection courses and the ICorr Trustees and CPGB, the Institute of Corrosion also offers an independent assessment of competence through its Professional Assessment Committee (PAC). This is recognised internationally as confirmation of experience, knowledge and task skills as defined in standard BS EN ISO 15257; it is valid internationally.

For cathodic protection companies and for independent cathodic protection specialists, attainment of cathodic protection training and certification will ensure demonstration of competence, experience and expertise. This translates into more effective work, improving reputational excellence, and more employment opportunities.

To learn more about our range of cathodic protection training courses and the experience and qualifications needed for certification, please visit our pages detailing the Cathodic Protection, Training, Assessment and Certification Scheme.

In our next article, we explode 7 cathodic protection myths.

From the Editor

From the Editor

Latest News

I hope you are all well, and that the restrictions are not causing too many problems for work. One indirect effect the pandemic is having on the magazine is that with companies shut down or working with fewer staff, and Institute of Corrosion meetings also cancelled, then there are less news items is this issue than normal.

However, we still have three technical articles, covering, inspection and the expert witness, a novel method of monitoring Corrosion Under Insulation (CUI), and an introduction to Microbial Induced Corrosion (MIC). There are also the two new columns, “Fellows Corner”, which this time covers Corrosion Monitoring and Inspection from Bill Hedges of BP, and “Ask the Expert”, in which the questions deal with salt contamination of steel, and impressed current CP of pipes. Remember to send your technical questions for answer by our industry experts.

If you have any comments or suggestions about the content of the magazine, please let me know, it is important that we are covering topics of interest to you the reader, remember it’s your magazine. Also send your technical articles for consideration to, brianpce@aol.com.

Keep yourselves and everyone safe.

Brian Goldie, Consulting Editor

The President Writes

The President Writes

Latest News

First of all, I hope you are all keeping safe and well. We are living through very challenging times and the future remains uncertain, which can be unsettling. My thoughts are particularly with those who have lost loved ones or whose livelihoods have been affected by the COVID-19 pandemic. Now more than ever the importance of community comes to the fore. The Institute of Corrosion is in many ways like a family, and we are determined to support our members in any way we can.

I will be highlighting below the ways in which we are continuing to provide services to our members through online platforms during the lockdown period, but we also have a duty to look after our more vulnerable members. If you require assistance with delivery of food or medical supplies or if you are living alone and would appreciate the opportunity to have a chat with another member (not necessarily just about corrosion!) please let me know by emailing gareth.hinds@npl.co.uk, and we will endeavour to help 
where possible.

We have been very pleased at the success of our online activities in recent weeks. The Corrosion Engineering Division (CED) Working Day on April 29 was attended by more than 50 people from as far afield as India and New Zealand, while the series of five webinars organised at the end of April by the Aberdeen Branch, in conjunction with the Marine Corrosion Forum, attracted over 100 participants to each event. I also gave a presentation at a World Corrosion Organisation (WCO) webinar to mark World Corrosion Awareness Day on April 24, which was attended by over 250 people.

In order to facilitate these and other events, the Institute has signed up to a Zoom Pro account, which is available for use by all branches, divisions and committees. This online meeting software has a number of useful features, including parallel breakout rooms, which were trialled very successfully for the five Working Group meetings during the CED Working Day. Please contact Head Office (admin@icorr.org) for details on how to access the Institute of Corrosion Zoom facility for online meetings and events.

Our Young Engineer Programme has also gone online. This year’s programme was heavily oversubscribed, with more than 60 applicants of which 32 were selected to participate, highlighting the success and growing popularity of the programme. The delegates will receive online training and mentoring in a range of corrosion-related disciplines and will work together in groups on an industry case study. Each group will present its solution to a panel of Institute of Corrosion judges in November – hopefully in person by that time! The winning team will be rewarded with a free trip to the NACE conference in Salt Lake City in 2021.

Training courses are an important component of the Institute’s commitment to upskilling and professional development of our members. We offer a range of online training courses (check the website for details) so if you are finding that you have time to spare during the lockdown it may be worth looking into attending one of these. It could be a valuable use of your time that will boost your career when life returns to normal.

Our social media activities continue to expand and I hope you are finding it easier to keep track of what is going on across the wide range of Institute activities. I encourage you all to share and comment on our posts and blogs to take maximum advantage of the functionality these digital tools provide.
Finally, I wish you and those close to you continued health and strength and hope that we will all have the opportunity to enjoy meeting in person again when we have made it through this difficult period.

Gareth Hinds, Institute of Corrosion President

ISO 12944 – Are You Meeting the Latest Standards in Corrosion Protection?

ISO 12944 – Are You Meeting the Latest Standards in Corrosion Protection?

Blogs, Latest News

Corrosion protection of steel structures by protective paint systems

First introduced as an eight-part standard in 1998, ISO 12944 was updated for the second time in 2018 with some significant changes and additions. Setting standards for coatings for steel structures in atmospheric, immersed, and buried environments, ISO 12944 now has nine parts. This article introduces the standard, answering the key questions that professionals in corrosion prevention ask about it.

What is ISO 12944?

ISO 12944 is a globally recognised standard that lays out the rules and guidelines for the protection of assets from corrosion by use of coating systems and paint. Having been introduced in 1998, it was updated in 2007 and revised a second time in 2018.

The standard covers paint and coatings for steel structures in atmospheric, immersed, and buried environments. It does not cover coatings for concrete, non-metallic substrates, high-temperature surfaces, chemical immersion, and other uses.

The standard covers three factors when dealing with protecting steel structures from corrosion:

1.      Corrosivity

The potential of the environment to cause corrosion. To achieve this, the standard classifies the environment into categories that are rated on their ability to corrode unprotected steel.

2.      Durability

The expected lifetime of the coating system until its first major maintenance. The standard also emphasises that inspection and minor maintenance should be expected throughout the lifetime of the structure.

3.      Coating system specifications

Based on the corrosivity of the environment and the durability of corrosion protection needed, ISO 12944 acts as a guide to selecting the coating system required for the steel structure to be protected.

Who should use ISO 12944?

The standard is designed for use by all those who have some experience and knowledge of either specifying, manufacturing or using paint and coatings to protect steel structures against corrosion in different environments.

Those who need to adhere to ISO 12944 include asset owners, construction companies, engineering companies, corrosion consultants, paint manufacturers and painting companies. Individuals who must work to the standard include:

What standards does ISO 12944 detail?

Within the nine parts of ISO 12944, standards are provided across the following themes:

1.      Corrosivity, environments, and categories (parts 2 and 9)

Environments are classified across several categories, with recommendations that cover atmospheric exposure, fresh and seawater immersion, and buried surfaces.

2.      Design considerations (part 3)

The standards covered here deal with the basic criteria for the design of steel structures that are to be coated to avoid premature corrosion of the substrate.

3.      Surface preparation (part 4)

Standards for the preparation of surfaces are given, with the objective of minimising the risk of premature failure of the coating system used.

4.      Protective paint systems (part 5)

The paint system used will depend upon the environment in which it is to be used and the intended durability, and ISO 12944 covers this.

5.      Lab testing methods (part 6)

Testing methods and conditions are detailed in ISO 12944. Testing should help users decide which coating system should be used, and so standardises testing to enable more accurate and comparable testing that acts as a guide (but not exact information) for determination of durability within a given environment.

6.      Execution and supervision of paint work (part 7)

As you would expect, the standard also deals with how coating of steel structures is executed and supervised, either on-site or in the workshop. The standard includes pre-treatment and paint application methods.

7.      Development of specifications (part 8)

Part 8 of the standard deals with development of specifications for the protection of steel structures from corrosion by using coating systems. These standards also apply to the protection of individual components, and cover new work and maintenance both on-site and in the workshop.

What changed in the latest revision?

The major changes in the 2018 revision were:

  • The Introduction of part 9, which discusses offshore environments and establishes a new ‘CX’ category.
  • Alterations to the categorisation of onshore environments.
  • The introduction of a new category for coatings used in conjunction with cathodic protection in seawater and brackish water environments.
  • Changes to durability standards, and the introduction of a new category for very long durability of more than 25 years.
  • Changes to minimum dry film thicknesses and the minimum number of coats to be used. These specifications have been made mandatory to bring a halt to the ‘race to the bottom’ in which paint manufacturers were producing increasingly thin layers to compete on cost.
  • Standards for testing have been updated, with new cyclical testing recommendations to better replicate on-site conditions.

The standard also recognises the need to remain innovative. It states that new technologies and innovative products can be accepted, but the manufacturer must demonstrate suitability by either reference to third-party product testing or a demonstrable track record.

In future articles, we’ll take a closer look at the changes and updates in ISO 12944. You can also read about them in Corrosion Management Magazine.

The Institute of Corrosion Coating and Inspection Training Courses – presented by Argyll Ruane and Corrodere – will help ensure your painters and inspectors work to the latest industry standards and benefit from new technology and innovative approaches. For more information, contact us today.

Corrosion Courses Opening Again

Corrosion Courses Opening Again

Blogs, Latest News

Is it time to boost your career with training and development (T&D) in corrosion?

It’s been a tough period for training and development in the corrosion prevention industry. Because of the coronavirus lockdown, it was necessary to move a lot of corrosion T&D initiatives online. Here at ICorr, we adjusted our training and development initiatives as fast as we could, to ensure that as few people as possible were negatively affected as possible.

In a recent blog, we described some of these initiatives, including:

We can now give you more great news. Another of our approved training partners, Argyll Ruane, is now open for business and once more delivering Institute of Corrosion courses designed to address corrosion issues facing various industries.

Back in the classroom – with a difference

On 21st May, 2020, Argyll Ruane was able to announce that it is fully back up and running, and that those wishing to book onto its Institute of Corrosion courses can do so now.

These on-site courses, held at their exceptional facility at the Sheffield Business Park, will now benefit from a range of measures to ensure your health and safety as we move to a new normal economy. Training processes have been adapted, and there will be PPE in place to aid student and staff safety as well as social distancing methods. It’s on-site delivery of training with a COVID-19 twist.

Though there will be many visible differences to how training is delivered, which may include distance learning for some course material where possible and appropriate, one thing has not altered – you’ll still benefit from trainers with years of experience in the field and in delivering exciting training experiences. You can be certain that the training you receive will be accompanied by real-world examples.

The benefits of being ‘in the classroom’

While the benefits of online training have become apparent to many, there are many benefits only available through on-site training. These include:

  • The human touch – a quality that is, thus far, impossible to replicate online. The interaction that is possible between students and staff in the classroom helps all to learn. You’ll learn from questions asked by others, and the experience of all participating in the training course.
  • A classroom setting – this also helps you to hone soft skills (such as interpersonal skills) and develop your professional network more effectively.
  • Health and safety measures in place – you’ll be learning in a safe, clean environment away from the pressures of work or the interruptions at home.

A wide range of training and development in corrosion prevention

All the ICorr training and development opportunities lead you toward industry standards with internationally accredited and recognised courses and certification that help to accelerate careers in your industrial setting.

Aspects of corrosion prevention that are covered by these courses include:

Re-certifications are available online for:

  • Painting Inspector Level 1
  • Painting Inspector Level 2
  • Insulation Inspector
  • Passive Fire Protection Inspector
  • Pipeline Coatings Inspector Level 2
  • Hot Dip Galvanising Inspector

Is it time to give your career a boost through T&D?

Training is critical for your career. It helps improve your skills and abilities, and makes you more attractive to current and potential employers. Developing your value in your professional capacity is a choice that helps you in all economic conditions.

Your training and development also benefit your current employer. You’ll perform your job more effectively, improve productivity, and be more satisfied in your role (and less likely to look for another job elsewhere). Happy employees are great advertisements for any business, and make it easier to attract talented new hires.

The answer to the question “Is it time to give your career a boost through T&D?” is always yes – whether through online or on-site methods.