Corrosion Inhibitors

Properly formulated engine coolants contain additives that inhibit corrosion, cavitation and scale formation in the cooling system.  Developments in engine technology has demanded advancements in coolant technology in order to meet the more complex requirements of manufacturers using lighter metals and plastics for the construction of engine and cooling system components.

Engine coolants are typically classified on the basis of the additive package utilised in the product.  There are three main categories of engine coolants from an additive technology perspective: Traditional Coolants, Hybrid (including Lobrid) Coolants, and OAT Coolants. 

Traditional Coolants

Traditional (or conventional) coolants are formulated with mineral (inorganic) inhibitors such as phosphates, silicates, borates, nitrite and other components.  Different conventional coolants will contain different combinations of these inorganic inhibitors to provide the corrosion protection required. These “traditional” inhibitors work by forming a protective blanket layer that insulates the system metals from the cooling fluid.  As a result of this method of corrosion protection, these inhibitors have relatively short service lives so require more regular monitoring and change-out.

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Hybrid (and Lobrid) Coolants

Hybrid technology coolants utilise a combination of mineral inhibitors and organic additive technology (OAT) inhibitors to protect against corrosion.  A distinction is sometimes drawn in this category between coolants containing predominately inorganic inhibitors ("hybrid") and those containing a predominately OAT inhibitor package with low levels of mineral inhibitors ("lobrid").  The combination of inhibitor technologies is broadly driven by regional preferences.  For example, Japanese and Korean OEMs prefer the use of phosphates over silicates, whereas European OEMs prefer silicates over phosphates.  

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OAT Coolants

Organic additive technology (OAT) coolants contain only "organic" inhibitors that are virtually non-depleting when compared to traditional inhibitors.  Coolants based on OAT inhibitors offer extended life corrosion protection and benefits from a compatibility perspective. OAT inhibitors work by creating a thin molecular layer at the corrosion sites, and - unlike traditional inhibitors - are not chemically consumed as they perform the function of preventing corrosion.

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