Conductivity of Engine Coolant and Antifreeze Solutions

Cavitation Corrosion of Aluminum Water Pumps

Conductivity of engine coolant as used in the vehicle is not a valuable measurement. It must be diluted to eliminate interference from the glycol.

Coolant conductivity is affected mainly by the concentration of glycol to water in the coolant. To a lesser degree,  the concentration of additives also has an effect. This is the effect that a few people are still trying to use to evaluate the serviceability of a coolant.

ASTM has not established a method for the industry, but a paper presented to ASTM by Dr. Rick Carr of The Penray Companies clearly illustrates that the conductivity of a coolant, taken from a vehicle, provides no valuable data because the effect of glycol is so overpowering. Dr. Carr goes on to show that, in conventional coolants, diluting the coolant 9-to-1 with distilled water does generate a more reliable field test to estimate the concentration of total dissolved solids in the coolant.

To make this method work, Dr. Carr's curves in the paper need to be used. Amalgatech has generated a similar set of data by repeating the experiments, graphed above.

Amalgatech further refined this approach by developing a curve for dilutions of coolant made in a ratio of 49-to-1. Amalgatech found that this dilution effectively eliminates the effect of glycols in the coolant, and predicts the actual TDS (total dissolved solids) concentration of the coolant. Because the dilution must be precise, this is probably a laboratory method.

Conductivity estimates of TDS in coolants is limited to conventional coolant technologies.

Thanks to Amalgatech for use of the chart.