Abstract: A system for evaluating the metal corrosion preventiveness of a coolant is disclosed, comprising a reference electrode (1), a working electrode (2) made of an iron material, preferably cast iron, and a voltage meter (3). The voltage meter is electrically connected with the reference electrode and the working electrode such that the redox potential to be generated between the two electrodes in the coolant (C) can be measured by the voltage meter when the two electrodes are partially submerged separately in the coolant. The system can provide an evaluation of the metal corrosion preventiveness of the coolant from the measurement of the redox potential. The cast iron for the working electrode may advantageously be surface-treated by tempering means or alkalization means.