Brass used in heat exchanger is corroded in industrial water. The used inhibitor is extracted from horse tail herb added in different concentrations and temperature to industrial water in which heat exchanger if exposed to these conditions. Brass is studied under the above conditions using potentiodynamic polarization, scanning electron microscopy (SEM) and X-ray diffraction. Potentiodynamic polarization technique was used to evaluate the corrosion rate data. Inhibition efficiency of 92.1 % at 298 k was achieved with the addition of 1350 ppm of horse tail herb from potentiodynamic polarization measurements. Potentiodynamic curves show that the presence of extracted horse tail herb in industrial water affects both the anodic and cathodic processes, decreases the corrosion current density and shifts the corrosion potential towards more noble values; the inhibitors are mixed type inhibitors.