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Chemical Limitations of Water

Published: 16/03/2015

Although water is cheap and readily available, it is also the root cause of corrosion within engine cooling systems.

Water when heated drives off a significant proportion of dissolved oxygen, but as it cools reabsorbs fresh oxygen. This cycle leads to a perpetual cycle of corrosion, which is accentuated in classic vehicles with no expansion chamber.

Water also acts as an electrolyte if dissolved solids, such as hardness salts (lime scale) etc., are present. This promotes galvanic corrosion where metals of high nobility sacrifice themselves to metals of lower nobility – this is often manifested by pitting.

Corrosion inhibitor formulations have changed many times over the years, but not always for the better. Nitrite, silicate, borate and azole based products have been around for many years, with Organic Acid Technology (OAT) inhibitors appearing more recently. OAT formulations are often branded as ‘Long-Life’ based on their five year life-span, compared with 1-2 years for standard antifreeze formulations.

Although OAT-EG-Water mixtures are now used in most new car engines, they have proven less successful in older vehicles and heavy duty diesel engines (HDDE). After several years of trying OAT based products many HDDE OEMs and fleet operators reverted to nitrite and/or Hybrid OAT (HOAT) formulations. One reason for this u-turn was that OAT formulations offer little protection against liner pitting.

To maintain effective inhibitor levels it is often necessary to retro-dose with Supplemental Coolant Additives or SCAs. It is common for SCA’s to be under or over dosed leading to accelerated corrosion rates, cylinder liner pitting or blocking up of radiator channels with congealed inhibitor.

Evans Waterless Coolants contain little oxygen and are comparatively poor conductors in comparison to water based coolants. Subsequently metal corrosion and coolant degradation is eliminated. For these reasons Evans Waterless Engine Coolants can be considered 4LIFE!

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