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Frequently Asked Questions

Some frequently asked questions about coolants, heat transfer fluids, use of antifreeze, etc.

If you cannot find the answer to your question in the FAQ section, please do not hesitate to contact us.

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What is the main function of a coolant?

The main function of a coolant is to transfer heat - primarily to remove the heat of the engine and to reduce the risk of overheating. A coolant also protects the engine against freezing and boiling and against corrosion, cavitation and erosion.

Do you have to dilute a glycol-based coolant?

Concentrated coolant can never be used in the application as such in view of heat transfer properties due to the high glycol concentration. In addition, compatibility with cooling system materials can be negatively affected.

In general a concentrated coolant is diluted in function of a targeted and/or required freeze point. Typical coolant concentrations do range between 40% and 50% and in some cases up to 60%;

What is OAT?

OAT is the abbreviation for Organic Additive Technology. It was discovered a couple of years ago that certain organic compounds (organic acids) provide outstanding corrosion protection on many kinds of metals and alloys. Arteco was one of the first to commercialise OAT coolants in Europe. The Organic Additive Technology gives long lasting corrosion protection because the organic additives do not deplete even after many operating hours or high mileages. OAT Coolants, such as Havoline© XLC, are often referred to as Extended Life coolants or Long Life coolants.

What is silicate?

Silicate is a mineral that is found all over the world and is a major constituant of sand, many rocks and stones. Silicate has to be extracted from natural sources in an energy consuming process before it can be used as corrosion inhibitor in coolants or in other applications such as construction material, inorganic fillers for plastics, paints and coatings or raw material for photovoltaic applications.

Silicate is a mineral or inorganic corrosion inhibitor with a relatively fast action on aluminium and aluminium alloys. It works by a formation of closed thin layers on aluminium surfaces. The disadvantage of that mechanism can be, as with many other mineral corrosion inhibitors, the hindrance of the heat transfer from aluminium engine parts to the coolant. In order to have a long term corrosion protection and good heat transfer on aluminium and on other metals and alloys, the silicate is almost always combined with OAT technology.

As inorganic inhibitor, silicate tends to agglomerate under demanding operating conditions of vehicles (passenger cars, heavy duty, ...) which compromises the corrosion inhibition on aluminium and its stability in the coolant. These problems are addressed in Arteco's silicate OAT lobrid coolants.

What is RA?

RA stands for “Reserve Alkalinity” and is a measure for the capacity of a coolant to take up acid, also called “buffer capacity”. Reserve Alkalinity is measured in terms of milliliters of 0.1 normal Hydrochloric Acid (0.1N HCl). The more milliliters the coolant can take up, down to a pH of 5.5 as defined in ASTM D 1121, the higher the Reserve Alkalinity is.

A high Reserve Alkalinity is often considered as a quality and performance guarantee. However, the RA has always to be considered in connection with the coolant technology of the respective coolant, i.e. Traditional, Hybrid, Lobrid and OAT–Technology and with the intended application. The RA of Traditional and Hybrid Technology ranges typically from 4-8 whereas the RA of OAT Technology and Lobrid Technology are typically situated around 3 ml 0.1 N HCl (50 vol% Ready Mixes, for more info please refer to our Product Information Leaflets). For historical reasons, in many heavy duty application high RA is still preferred, whereas the low RA technologies seemed to be more appropriate for passenger car and light duty vehicles. With increasing heat and mechanical stress in both, heavy duty and passenger car applications, also the low RA coolant Technologies, OAT and Lobrid, find their way into heavy duty applications. The additives providing high reserve alkalinity tend to become unstable under high heat and mechanical stress.  

What is pH?

pH is the negative decadic logarithm of the hydrogen ion concentration. It is a scale to specify how acidic or basic a water based solution is referring to the pH of pure water. Pure water displays a pH of 7 which is also designated as “neutral” or “neutral pH”. Water based media with pH values below 7 are called acidic, pH values above 7 designate the basic pH range. The maximum possible pH of water based systems is 14 (e.g. concentrated caustic soda) and the lowest is 0 (e.g. concentrated mineral acids).

As coolants (concentrates and ready mixes) are strictly speaking due to the presence of glycol no longer water based systems, the correct measurement of pH value in a coolant in operation necessitates a specific procedure that should be carried out on the basis of a sample in a specialized laboratory. Measurement of pH of coolants with commercially available pH strips will produce misleading results. The correctly measured pH in a coolant sample is a good indicator of the end of life of a coolant, in general terms a pH of 7 should lead to a closer inspection of the coolant and potentially to a renewal of the coolant.

The desired operating pH range of a coolant is pH 7.5 - 9 as many metals and metal alloys present in a cooling system are least prone to corrosion in that pH range and most additives and corrosion inhibitors are at their optimum activity in this pH range.

What is density and how is it affected by base fluid concentration?

Density by definition is mass per unit volume.
Example: 1 liter of water weighs 1.0 kg at 4°C, so the density in this example is 1 kg/liter. At this temperature water has its maximum density or lowest volume since the water molecules are optimally arranged.

Obviously density of a substance varies with temperature and pressure. Pressure dependency is typically limited for solids and liquids, but is much higher for gases.
For binary systems - such as a water/glycol mixture - density varies also with the concentration ratio of both substances. Considering a mixture of water and MEG at a certain temperature, the density moves to higher values by adding more MEG to the mixture.
As a result, 90vol% Havoline® XLC has a higher density (1.107kg/L at 20°C) compared to 40vol% Havoline® XLC (1.056kg/L).

Mixtures of water and MPG however do not follow the same behaviour. At a given temperature the density of water/MPG will start to decrease once the concentration of MPG has reached about 80vol%. The reason for this is a steric hindrance of the methyl group of the MPG molecule for MPG concentrations above 80vol%, which is the result of a non-optimal arrangement of water and MPG on molecular level.

What is Electric Conductivity?

Electrical Conductivity (EC) or specific conductance represents the ability of a matter (solid, liquid, gas and plasma) to allow the transport of charged particles. A high EC indicates a material that readily allows electric current.

EC is commonly signified by the Greek letter σ (sigma), but also κ (kappa) and γ (gamma) are sometimes used. The SI unit (International System of Units) of EC is Siemens per meter (S/m), whereas for engine coolants and heat transfer fluids (HTFs) µS/cm is often used.

In electrolytes such as an engine coolant or HTF, electrical conduction happens by ions - which is the collection of anions and cations - traveling, each carrying an electrical charge. The conductivity of ionic solutions/electrolytes varies with concentration of ions and temperature. Think about distilled water as an almost insulator whereas salt water is a reasonable fair conductor. 

As can be understood from the above, the quality of the dilution water itself (linked to the total ion content) plays an important role in the EC of the coolant. Secondly, the inhibitor  technology is affecting the EC level as well.  And in addition, when the coolant or HTF is circulating in the system it might pick up remnants from machining and other contaminants, all having an impact on the overall EC. It is therefore incorrect to deduct from the EC value the dilution ratio of an engine coolant or HTF.

How to select the right sample analysis package?

The best-fit analysis package depends on the application, the frequency of sampling, the condition of the coolant, the condition of your engine/system, the reason for taking a sample, …   Here below are some general guidelines. 

  • Select BRONZE if you perform already regular checks and are closely monitoring your coolant quality (f.e. via monthly sampling).  It also serves as good alternative for less accurate in-field measurements.   This will result in better insights on the current condition of your coolant properties
  • Select SILVER if you wish to obtain an overall view on your cooling system via determination of corrosion, contaminants & other metal components.  This package is also ideal to detect potential deterioration of your coolant by analysing degradation products and other anions. 
  • Select GOLD if you want to attain a complete chemical evaluation of the coolant, including a detailed corrosion inhibitor analysis.  This package gives you a full picture on the composition of the coolant, its condition and a potential contamination or deteriorationt.  
  • Select the MICROPATCH as extra analysis in case of hazy samples or samples with clearly visible deposits.  By separating the deposits via filtration, and a microscopic analysis of the deposits, interesting learnings will lead to better understanding of the nature of the deposit, the cause and eventually how to address the problem.  
What is flux?

Flux is a chemical, a so-called process aid, also known under the name nocoloc (Solvay trademark name). It is used in the welding process of aluminium heat exchangers. Flux prepares the aluminium surface for the welding process and reduces substantially the welding temperature. Flux remains as a flux residue in the inside of the finished aluminium heat exchanger.

What are the consequences of flux interacting with an engine coolant?

As Flux remains as a flux residue in the inside of the finished aluminium heat exchanger after the welding process, the remaining flux comes into contact with the coolant at the moment of the filling process of the cooling system.  Flux will interact with the corrosion inhibitors present in the coolant, and the interaction is different depending on the type of inhibitors.

Mainly inorganic corrosion inhibitors such as silicate have a high risk to interact with the remaining flux. The potential long term consequences are reduced availability of silicate for aluminium corrosion protection and the formation of gelish deposits. The deposits tend to block narrow ducts and/or channels in the cooling system particularly in heat exchangers.

This phenomenon is partially prevented by the heat exchanger manufacturers by extraction of flux residues from the aluminium heat exchangers which is a costly process. The better way to prevent this is to use Arteco's silicate-free OAT based or silicate stabilised coolants.