Abstract: Disclosed is a corrosion inhibitor for use in heat transfer fluids having a conductivity of less than 200 ?S/cm, the corrosion inhibitor having an azole compound, and at least one of a siloxane based surfactant, colloidal silica, or a mixture thereof. Also disclosed is a corrosion inhibiting heat transfer fluid, the heat transfer fluid having a conductivity of no more than or equal to 200 ?S/cm and comprising the disclosed corrosion inhibitor. Also provided is an assembly comprising an alternative power source and a heat transfer system in thermal communication with the alternative power source, the heat transfer system comprising the disclosed corrosion inhibiting heat transfer fluid. In addition, a method of making a corrosion inhibiting heat transfer fluid is disclosed wherein the disclosed corrosion inhibitor is added to heat transfer fluid having a conductivity of less than 200 ?S/cm.