Coolant protection for aluminum radiators and cooling systems

A few years ago, off-highway equipment OEMs introduced aluminum radiators and engine cooling systems manufactured with the Controlled Atmospheric Brazing (CAB) process. These are lighter and less expensive than the old copper radiators, but as with any change in equipment standards, they present new challenges.

Where the older metal radiators were soldered together, the CAB process refers to brazing (or joining) the aluminum parts together using a flux or chemical cleaning agent to prepare the aluminum for brazing. The outside of the radiator that is exposed to the atmosphere becomes oxidized or passivated, meaning a natural protective coating forms on the aluminum. However, inside the radiator, the aluminum treated with the flux remains unpassivated, or lacking in that protective layer.

When a coolant is introduced, particularly if it contains nitrites, it has a tendency to react with the unpassivated or unoxidized aluminum. This reaction can cause the formation of precipitants that clog small orifices in the cooling system. It can also upset the pH balance of the coolant itself, causing it to break down. In a nitrite-free coolant, depending on the additive chemistry, the presence of flux can change the concentration of the additives in the coolant, which has the effect of diminishing coolant life.

Some manufacturers, including Caterpillar and Navistar, have addressed the issue by offering an aluminum conditioner that effectively passivates the metal inside the radiator. This allows for the use of a coolant containing nitrites, which Caterpillar recommends for protecting cylinder liners from cavitation, while mitigating the problems caused by the unpassivated aluminum and flux. While some manufacturers have gone to a nitrite-free organic additive technology (OAT) specification due to the aluminum radiator issue, Caterpillar still calls for nitrited OAT or NOAT coolants. Most equipment users in North America, therefore, are still using NOAT-based coolants, even if they have mixed fleets, and using the aluminum conditioner in new equipment or when replacing older radiators.

Caltex Coolant Solution

At Caltex, we have come up with an alternative, which is to change the composition of the coolant rather than treating the aluminum with a conditioner. Our new Delo® ELC Advanced extended life coolant is a NOAT formulation with patented technology that controls the reaction with the aluminum and the flux to extend system and coolant life. With Delo ELC Advanced, equipment operators will no longer need to rely on a conditioner to just reduce the risk of a chemical reaction with the nitrite and unpassivated aluminum in their coolant systems.

We are further planning to introduce Delo® XLC Advanced coolant for on-highway vehicles that tend to use the non-nitrited OAT-based coolants. So, on the road or off, Caltex has your back when it comes to protecting your cooling system.

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By Dan Holdmeyer - 20 June 2019

About Author

With over 35 years in the oil and gas industry, Dan Holdmeyer has worked for Chevron the past 14 years, serving in a variety of capacities with the company in addition to his current post as Industrial and Coolants Brand Manager where he works as a lubrication engineer that supports Chevron Delo and other related lubricants brands. He plays an integral role in supporting and managing a variety of programs related to off-highway and on-highway lubrication needs. Dan also works as Chevron’s Training Specialist for their Global Lubricants division since joining the company. Prior to joining Chevron, Dan worked as a Field Engineer at Mobil Oil Corporation for 20 years (1979-99) after graduating from the University of Missouri-Columbia with a Bachelor of Science in Chemical Engineering.

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