Synergistic Inhibition of Carbon Steel Corrosion by Inhibitor-Blends in Chloride-Containing Simulated Cooling Water

The objective of this work was to develop efficient synergistic inhibitor combinations comprising sodium nitrite (NaNO₂) and an inhibitor-blend code named (SN-50), keeping in view of their application in industrial cooling water systems. The electrochemical characteristics of the carbon steel working electrode in simulated cooling water (SCW), without and with the addition of different combinations of the inhibitors, were investigated using electrochemical impedance spectroscopy (EIS), open circuit potential (OCP). The electrode surface changes were followed by visual characterization methods. It was demonstrated in this study that all the combinations of the inhibitors exhibited synergistic benefit and higher inhibition efficiencies than did either of the individual inhibitors. The addition of SN-50 inhibitor to the SCW shifted the OCP to more anodic values and increased the polarization resistance (R_p) values of carbon steel at all applied concentrations. The higher the applied sodium nitrite concentration (in the protection concentration range), the higher the obtained R_p values and the inhibition efficiency improved by increasing the inhibitor concentration.