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Vehicle heat exchangers are exposed to a number of aqueous environments ranging from inhibited coolants to seawater. Frequently, the design of the heat exchanger results in a galvanic couple between copper and a stainless steel. This couple can either prevent or promote pitting and crevice corrosion of the stainless steel member. This paper demonstrates the use of electrochemical corrosion measurement techniques to predict this behavior. Stainless steels which have acceptable, marginal and unacceptable resistance to localized corrosion when coupled to copper in aggressive environments are described. Potentiodynamic polarization curves for a variety of stainless steels were measured in artificial seawater to determine their pitting and critical protection potentials. Mixed potential measurements for these alloys galvanically coupled to copper were then made to predict the localized corrosion behavior of the stainless steel.

The increasing use of aluminum for engine and cooling system component design has resulted in the need for improved monitoring of cooling system performance. These new systems are more susceptible to damage from corrosion and overheating. A sensor is now available that responds to inhibitor depletion and to low coolant level in service. This device combines sensing electrodes and electronics into a package that mounts directly onto the radiator and provides a compatible vehicle computer output. This paper describes the design, application, and performance of this sensor.