As I walked through my laboratory, a recent case caught my attention. A client had sent in a sample of engine coolant that appeared in good condition based on standard refractometer readings. There was not any visible sediment or sludge, there was little to no corrosion elements present and the pH was still within acceptable tolerances. Now in coolant analysis that can be a rare thing as I see some horrible looking coolants come in on a daily basis. However, upon deeper analysis using ion chromatography, we discovered a startling level of glycolate ions – a clear sign of glycol breakdown suggesting the coolant needed changing before it started attacking the coolant system. This case perfectly illustrates the critical importance of ion chromatography in analysing engine coolants.
Engine coolant testing is one of the most inconsistent test suite between labs. Many labs I see doing a freeze point from a refractometer and a few simple corrosion elements only. Others do a couple dip tests and a glycol percent. To call what is on offer basic would be an underestimate. I have always prided in our lab doing more detailed testing as standard including visuals, glycol percent, freeze point, coolant corrosion inhibitors, corrosion elements, tap water ingress checks, pH, microscopy and more, however the thing you will discover working in a lab that no matter how detailed your testing is there are always more tests you can do.
That is why our lab is constantly investing in new instrumentation and methods at a rate I have to think sometimes have we got the instrument already, and I have had to build a second lab to fit all the instruments in.
Now to do every conceivable test on any sample type is non-sensical as it would cost millions and take months or years to perform. Hence why most labs tailor a suite usually on price first and foremost and secondly on diagnostic data. In contrast we start with what we need to give a good diagnosis and then work from there. However, there are occasions we can see certain tests are not necessarily needed on every single sample to be considered routine but on critical systems these add-ons or diamond upgrades as we call them in the lab can be used to give some much needed additional information on your machinery.
One of these tests for engine coolants is called ion chromatography or IC for short, which we will cover in today’s article.
Fundamentals of Ion Chromatography – Understanding Ion Chromatography
Ion chromatography is a process used to detect and measure specific ions (charged particles) in a water based solution. This technique separates ions based on their interaction with a stationary phase and a mobile phase in a chromatographic column. This may seem complicated but you have done something similar as a child in dropping ink on blotting paper. The ink powder is separated in the mobile water phase by the stationary blotting paper. Now IC is a more high tech and precise form of this principle allowing to separate the individual components of the coolant out and to measure them. The result looks like below with the different anions coming out at different points along the timeline.
A typical ion chromatography trace of a sample
The results offer a detailed insight into the chemical composition of the sample. Now those of you astute enough to notice we are already measuring with routine analysis a breakdown of the chemical elements present with ICP to give you total sodium, potassium etc of the coolant, but these are only measuring chemical elements and on the whole mostly only the cations rather than the anions. Don’t worry I know what your next question will be so I cover that next.
What are Cations and Anions?
In the realm of chemistry, ions are atoms or molecules that have lost or gained electrons, thus acquiring a charge.
If we take table salt for instance you may know this is sodium chloride or NaCl. However when you put it into water it dissolves and turns into ions of sodium and chloride, one with a positive charge and one with a negative charge so it forms Na+ and Cl- ions.
Cations are positively charged ions, typically formed when an atom loses electrons. Anions, on the other hand, are negatively charged ions, created when an atom gains electrons when the bond between the elements break and they dissolve into solution.
I recall in class at school struggling to remember cation and anion as which was positive and negative the morning before an exam as cats always come across as feline or feminine in my head and I struggled to break that association. Just then a boy called Edward who later went on to do physics laser optics research, got down on the floor in class, started meowing and said “Cat’s are very positive” to roars of laughter all round. I still see that in my head if I struggle to remember the difference. The scene was a bit like below if you are struggling to picture yourself.
Cat’s are very positive. How to remember Cation and Anion as positive and negative
In engine coolants, both cations (like sodium and potassium) and anions (like chloride and sulphate) play crucial roles. Monitoring these ions helps in understanding the coolant’s condition, its corrosive properties, and the potential for scale formation.
Can’t you work out the anions from the cations?
Now for the chemistry whizz’s amongst you, you may be thinking monitoring the sodium and potassium you can work out the the anions by their concentration and don’t need to test anions? That is true if you know there is only one possible anion. However, take sodium, that could be sodium nitrite a corrosion inhibitor or sodium chloride salt, one is beneficial and the other is not and the chlorides can actually be corrosive to cooling systems. Likewise calcium and magnesium can be sulphates from hard water, sulphonates from engine oil ingress, carbonates from dissolved carbon dioxide forming carbonic acid. So as you can see knowing the cations only gives half the picture. In the case of sodium and potassium even knowing no salt water is present, the anion can change as the coolant ages such as nitrites convert to nitrates as the coolant ages and the additive is spent. Even if you use non nitrite based corrosion inhibitor coolants and just a glycol and water mix the glycol itself can degrade producing glycolates as observed in the case study at the start of this article.
Glycol Breakdown and Glycolates
Glycolates are salts and esters of glycolic acid and are formed as a result of glycol breakdown in coolants. While a refractometer can measure the concentration of glycol, it cannot detect the breakdown products like glycolates. So you may have say 55% reading on the refractometer and believe you are well covered but if this is made up of significantly degraded glycol the performance of the coolant will be poor and can even damage the cooling system generating deposits and lead to machine failures. These breakdown products are critical indicators of the coolant’s health and its protective capabilities.
Nitrates and Nitrites
Nitrites are often added to coolants as corrosion inhibitors. However, their levels need to be monitored as excessive amounts can lead to issues like water pump failure or corrosion.
Nitrites are known for their capacity to prevent the oxidative corrosion of metals like cast iron and steel, which are commonly found in engine cooling systems. They help maintain the integrity of these components, ensuring efficient heat transfer and prolonging the life of the engine. They work by aiding in reducing pitting corrosion, a more localized and potentially more damaging form of corrosion. This makes nitrites especially important in heavy-duty engine applications where the risk of pitting is higher.
As the nitrites degrade they convert to nitrates so measuring the balance of nitrites to nitrates helps identify the condition of the corrosion inhibitor.
Despite their effectiveness, the use of nitrites has seen a decline. Concerns over environmental impact and health risks associated with these chemicals have driven the development of more eco-friendly coolants. The industry is increasingly adopting Organic Acid Technology (OAT) and Hybrid Organic Acid Technology (HOAT) coolants, which utilize organic acids as corrosion inhibitors. These coolants offer a safer alternative and often have longer service lives, reducing the frequency of coolant changes, if well maintained. Notice the well maintained caveat at the end there; don’t go thinking this means monitoring anions isn’t important in these products or they last much longer. As a general rule, environmentally friendly introduces new headaches and problems to combat as they tend to be far more temperamental to slight condition changes making them even more important to monitor than the more traditional coolants.
Now, first let me start before I get the letters in complaining ‘you oil companies all hate environmentally friendly’, I am one of the biggest advocates of environmentally friendly machinery fluids. We are one of the bigger labs in this area helping new fluid suppliers do research in this area and I personally think those that don’t get onboard with progress will be left out of a job over the next decade. However, although this is the direction of travel and is good for the planet, it doesn’t mean it isn’t without its problems which should be highlighted in a honest impartial view of an independent laboratory. Generally, environmentally friendly is at the expense of the machine life. Take an example of exhaust emissions of vehicles producing acid rain and sooty ash deposits that have been linked with various health conditions. Nobody I think would disagree reducing these emissions is a bad thing and the last 20 or so years have seen dramatic reductions. For instance reducing sulphur in fuel has been a big success, but sulphur is an excellent lubricant and so the ability to lubricate has been dramatically reduced as a result and vehicle fuel system faults have increased as a result because of this failure mechanism. Likewise, exhaust gas recirculation has helped reduce exhaust emissions, but the chemistry of combustion hasn’t changed so rather than all these acids going out the exhaust they are not dumped back into the engine oil making it have to work even harder. Combined with the trend to much longer oil drain intervals to reduce waste your oil is fighting harder for longer in a harsher environment. So the need to monitor is even more key. Hence, if you think about it, environmentally friendly makes fluid analysis even more critical. So if I ever highlight the disadvantages of environmentally friendly, it’s only to emphasise why you need to test more than to argue against making the change.
Effects of environmentally friendly machine fluid changes
Even if you use OAT or HOAT coolants measuring nitrites can be helpful to identify mixing of coolants as just measuring sodium will only identify a corrosion inhibitor is present and knowing if it’s bound to a nitrite or organic acid such as sebacate anion helps in identifying if the correct coolant is used.
Chlorides, Fluorides, Sulphates
These ions, often found in tap water used to mix coolants, can be highly corrosive to the cooling system. Chlorides can lead to pitting and corrosion of metal parts, while fluorides can react with other coolant components. Sulphates and carbonates can form hard water scales that reduce system cooling similar to what you see in your kettle. So now you understand what we test let’s cover how we measure these anions.
Why Consider Ion Chromatography for Engine Coolants?
Standard tests like refractometry only provide a partial picture of coolant health. Ion chromatography delves deeper, offering detailed insights into the chemical composition and potential issues to compliment the cation analysis your lab should already be offering as standard.
When should I use IC?
As an annual or 6 monthly checkup
If you do quite regular monitoring of your cooling systems say once a month or so when doing your routine oil samples for industrial engines then unless the engine is critical then you probably don’t need an IC analysis on every sample. Perhaps leaving this to a 6 monthly or annual check. However, if you seldom visit the engine and perhaps only sample a couple times a year then you really should consider adding IC into the mix to keep an eye on coolant health beyond the routine.
As part of a regular Preventative Maintenancepackage on key assets.
Regular ion chromatography can identify problems before they become major issues, saving costs on repairs and downtime. Your routine analysis will identify a lot of issues but if you want to cover all the bases, especially as 80% of all major engine failures are cooling system related.
To make a decision on a coolant change or as part of a major overhaul
If you have not visited an engine for a while, are looking to buy one, or taking on a new service contract you should really check the coolant condition and include IC to get a full picture of the health together with the oil and fuel analysis.
Conclusion: A Comprehensive Understanding for Informed Decisions
In our laboratory, we see countless cases where regular coolant testing could have prevented significant engine issues and failures. I strongly advocate for regular, detailed coolant testing. It’s not just about the current condition, but about predicting and preventing future problems.
For more information or to discuss your specific needs, feel free to reach out through the ‘blue Contact Us’ button on this page. Stay informed, stay ahead, and ensure your engine’s longevity with the right analysis.
