Corrosion inhibition using nitrogen

Nitrogen, acting as a supervisory gas in piping, is a well-documented inhibitor of corrosion and has been implemented in industries such as gas and oil, pharmaceutical and the marine transit industry. Historically, dry and pre-action fire suppression systems have used compressed air as the supervisory gas to pressurise piping, however, it contains both oxygen and moisture causing the system piping to corrode leading to failures resulting in property damage, production downtime, and increased maintenance costs. Additionally, corrosion impacts system hydraulics and reduces the efficiency of fire sprinkler system designs.

A study conducted by Potter Electric Signal1 analysed the corrosion-inhibiting effects of 98% nitrogen gas when applied to both carbon steel and galvanised steel, in an environment simulating a dry pipe fire sprinkler system. The weight loss methodology is utilised to examine the effects.

dry and pre-action systems are the world’s second most common type of fire suppression system. With increasingly widespread use of these systems, attention has turned to the issue of corrosion.

Initially, galvanised pipe was preferred for use in dry or pre-action systems with the expectation that galvanised pipe would experience less corrosion. When pipe is galvanised, its walls are coated with zinc to reduce the detrimental effects of corrosion on steel as it acts as a sacrificial material by first reacting with corrosion-forming components, thus creating a protective layer of scale build-up and protecting the steel. Widescale adoption of galvanised piping in dry and pre-action systems, along with multiple decades of use, has resulted in unfavourable performance. In fact, case studies have shown that due to oxygen cell corrosion, pinhole leaks begin developing within two years after installation of a galvanised dry system, while ruptures have occurred within four years.

A survey evaluating the internal conditions of dry sprinkler systems for two decades was performed by the notified body, VdS. It indicates that more than 70% of the current dry pipe systems have to be treated for corrosion within 12½ years, of which some 20% of the systems will have to be almost fully replaced (EFSN 2009). In NFPA 13 – 2013, the performance of galvanised pipe was recognised to be no better than that of black steel pipe. The need for corrosion protection in dry and pre-action sprinkler systems became evident and one such corrosion prevention technique is replacing the supervisory air with nitrogen gas.

One key attribute of nitrogen gas is its general inability to react with metals… To comprehend why nitrogen, unlike oxygen, does not cause corrosion to propagate, it is important to understand the corrosion mechanism. Generalised corrosion reaction is caused by production of electrons which are produced and then consumed in the cathodic reaction by dissolved oxygen. This process causes uniform corrosion, but can be inhibited by limiting one of the reactants, such as oxygen.

The specific issue with dry and pre-action systems, when compared to typical wet systems, is the abundance of oxygen supplied by the air compressor. The Potter study was specifically designed to see the relative difference between using nitrogen gas over air and its effect on corrosion rates. Corrosion testing of black steel sample strips and galvanised sample strips under simulated dry and preaction conditions was conducted to evaluate corrosion inhibiting benefits of 98% purity nitrogen gas compared to compressed air in systems half filled with water and systems which contained no significant quantity of water. The systems half filled with water were used to create a trapped water condition often found in dry and pre-action fire suppression systems due to inadequate draining, which results from system design layout limitations.

The purpose was to compare the relative differences between using 98% nitrogen and compressed air in a variety of different applications.

In every environmental condition, 98% nitrogen resulted in a lower metal loss when compared directly to compressed air. This was also visibly apparent when the corrosion sample strips were removed from the testing manifold. The most noticeable differences were observed when comparing 98% nitrogen to compressed air for the galvanised sample strips. The corrosion sample strips exposed to 98% nitrogen had more uniform corrosion deposits than those exposed to compressed air. This was evident for pipes half filled with water as well as drained pipe setups.

Inhibition effectiveness is measured as the percent reduction in metal loss when using 98% nitrogen as compared to the same conditions using compressed air. Depending on the environmental conditions, using 98% nitrogen in lieu of compressed air decreased metal loss from 45.4% to 91.8% with an average of 69.4%.

Nitrogen gas

The largest improvement was noticed in a dry galvanised system which resulted in a 91.8% corrosion reduction.

Percentage protection was used to calculate how much longer a system would last, on average, under supervisory nitrogen compared to compressed air… For example, assume a steel system half filled with water has a life expectancy of 15 years when using supervisory air. If the system used supervisory nitrogen, the expected life of the system would increase from 15 to 70 years (15 years X 4.7 = 70.5).

The metal losses under every condition were lower when using black steel when compared to galvanised steel. Visual inspection of the galvanised sample strips indicated the sacrificial zinc layer was compromised, exposing the steel to accelerated corrosion. At the exposed steel surface, a defined pitting mechanism was observed. Conversely, the black steel sample strips corroded more uniformly.

This study concluded that

1. The use of 98% nitrogen in lieu of compressed air as a supervisory gas reduces corrosion in both galvanised and black steel systems regardless of whether or not trapped water is present.

2. The corrosion reduction potential ranges from 48% to 91% when compared to compressed air.

3. Using 98% nitrogen gas in lieu of compressed air increases the life expectancy of a dry or pre-action system on an average of 5.3 times.

4. The use of galvanised steel instead of black steel results in higher metal loss rates when compared in equivalent environments.

5. The use of 98% nitrogen gas in a relatively dry, black steel environment has the lowest corrosion rate overall.

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So, who is Paul Dutton?

My personal experience has been gained over 34 years as a leader within the UK military and Police Service where until January 2023 I was Director of Multi Agency Gold Incident Command training for the UK, College of Policing. I have held command positions at Strategic, Tactical and Operational level within the Police Service. I have worked on numerous overseas humanitarian operations for the United Nations, NATO and the Foreign and Commonwealth Development office and I led the UK, International Police Response Cadre for seven years delivering disaster management response and training across the world.

What inspired you to found GSB Command Training?

In less than 100 days in 2017 more than 100 innocent members of the public lost their lives in the United Kingdom as victims of multiple, devastating incidents: building fires, terror attacks and natural disasters.

The Grenfell Tower Fire, Manchester Arena Bombing, Westminster Bridge terrorist attack, flooding and wildfires were all declared Major Incidents, defined in the UK as; “An event or situation with a range of serious consequences which requires special arrangements to be implemented by one or more emergency responder agency”.

In the ensuing six years, I questioned whether we were better prepared to respond at pace, to save lives and reduce harm.

Over the last 3 years I have trained, tested and exercised over 1000 strategic and tactical commanders from the Fire, Ambulance and Police Service. My experience is that all commanders arrive for their multi agency command course well trained and highly skilled in their own organisations systems and processes. As individual organisations we all have a 24/7 ‘on call’ system which works well during our day-to-day business. What we do very well is train regularly for single agency response incidents which happen frequently, as a consequence we and in particular the Fire Service is excellent at single agency emergency response. What we fail to do so well is plan and train for those low frequency, high risk major incidents which may only happen to us once in our career, if we are lucky.

Are YOU ready? Is your organisation ready?

Experiences of the multi-agency emergency services preparedness for high impact, low frequency events with paul dutton , Director of GSB Command Training.

Can you expand on your concerns?

During the first hours of the response to the Manchester Arena Bombing on 22nd May 2017, the whole of the on-call command team for Greater Manchester Fire and Rescue Service convened at their single agency command suite, no one attended the Multi Agency Silver or Multi Agency Gold groups. The failure to implement the primary JESIP1 principle of Co-locate caused a 90-minute delay for the Fire and Rescue service to arrive at the scene of the attack, this failure has been heavily criticised throughout the Manchester Arena Attack Inquiry.

At the Grenfell Tower Fire the executive leaders for London Fire Brigade responded quickly with the Commissioner attending the scene and entering the building while it was ablaze. These actions were considered heroic by many in the service and beyond however these actions were later brought into question during the inquiry. London Fire Brigade has subsequently changed its policy, the Commissioner and Deputy Commissioners no longer attend the scene of incidents. This change is designed to distance the most senior leaders from the scene of and provide the protection, which was not available to the Commissioner during the Grenfell Inquiry. After a challenging time at the inquiry the Commissioner retired from service earlier than planned.

So why does this happen? With years and years of training why do you think commanders of the emergency services still make mistakes when responding to Major Incidents?

I believe the answer lies in a failure to personally prepare.

We fail to personally prepare ourselves for the day the ‘big job’ comes in. We take being ‘on call’ for granted, it is just another part of our job, it comes with promotion. We are so busy with our day to day business we often don’t give being on call a second thought until we are leaving the office and need to grab our additional ‘on call’ kit and equipment. We have local plans and major incident plans but do we all really know what our role is within those plans?

Imagine, it is 0300, you are in bed, fast asleep, you are the on-call Gold or Silver Commander for your organisation. The phone rings, you answer it, half asleep, to be told by a wide awake and nervous control room operator that an aircraft has crashed or there has been a gas explosion in a busy night club. The incident is 15 minutes old and it is already believed that fatalities are in double figures with over 50 injured at the scene. How are you going to respond? how are you going to take up a command role which adds value to this response, saves lives and prevents the incident from getting worse?

Those commanders who have trained for this will instinctively recall their training and start to put into place their personal response plan. In the last few months, I have received 2 emails from commanders who told me their recent command training and personal response plan gave them the knowledge and confidence to respond quickly and effectively when they were faced with a mass casualty major incident.

Can you tell us more about major incident scenarios?

There are 2 types of major incident.

A Rising Tide, Covid 19 is probably the best example of this, a major incident (Pandemic) which is heading towards us, and we have time to prepare. The second and most problematic is a ‘No Notice’, sudden onset incident.

How does the training you offer make a difference?

A ‘No Notice’ incident requires commanders to react quickly, with no time to prepare. Throughout our careers as Sector or Incident Commanders we are trained to get to a scene as quickly as possible to tackle the incident. As strategic commanders our response must be different. When the shock of a major incidents hits us and the adrenaline is pumping around our bodies we need to ‘keep our heads’ while those around us are losing theirs. Coordinated Strategic and Tactical Command in an emergency is crucial, it allows for the coordination of resources and response effort to maximise efficiency and effectiveness. With the correct training I believe 50% of a strategic commanders’ immediate response work can be pre planned, prepared and tested during peace time. Truth is, many of the core roles for commanders in the event of a major incident are already set within our plans or government documents. The problem is, we have so many plans and documents many of them are sat on the shelf unread.

As seen in the Manchester Arena attack when strategic command fails during an emergency it can lead to a disorganised and inefficient response. Valuable resources may be misallocated or not utilised effectively causing delays and potentially exacerbating the situation. In extreme cases failure of strategic command can result in loss of life, damage to property, and longer-term consequences for affected communities.

But surely, emergency preparedness, response and recovery is not one size fits all? Drawing upon my personal command experience and the experiences shared with me by commanders from across the globe I lead GSB Command Training with a single focus, to provide bespoke, world class training which will prepare commanders to optimise their ability to respond quickly, save lives and reduce harm.

Within my small team of subject matter experts, I have a former Chief Fire Officer and a barrister who specialises in training commanders to understand their legal duties and prepare for an inquiry.