A method has been developed of initial assessment of the effectiveness of steel corrosion inhibitors in cooling water, in order to determine the manner of water inhibition in a pilot cycle or directly in the industrial cycle. Electrode linear polarizations have been measured in the range of +/-(10-20) mV in series, 8 model stands each, with various conditions of water preparation. The examination of samples of water from the cooling systems of a continuous caster of one of steel plants indicated that there is a possibility of determining the protective properties of inhibitors within 20 h-which has been confirmed with direct gravimetric measurements.