Synergistic Effect of Iodide Ion and 4-Hydroxy Coumarin on the Corrosion Inhibition of Mild Steel in Hydrochloric Acid

Abstract

No discussion of the use of inhibitors in acid solution is complete without mentioning the phenomenon of synergism. Synergism also operates in corrosion protection where an enhanced inhibition may be related to interaction between inhibitor compounds. This effect has been observed since the earlier days of inhibitor technology and continues to be a potent tool in the development of acid inhibitors for specialized uses. Hence, in this paper, the corrosion inhibition behavior of mild steel (MS) in 1 M hydrochloric acid in the presence of 4-hydroxy coumarin (4HC) and potassium iodide (KI) has been investigated using the mass loss method and electrochemical techniques. The inhibitive performance of 4HC is considerably enhanced by the addition of KI. The addition of KI to different concentrations of 4HC has intensified its efficiency through considerable reduction in the mass loss, corrosion current density , double layer capacitance , and increase in charge transfer resistance . The calculated synergism parameter “” is greater than unity, thereby proving the fact that the improvement in inhibition efficiency of 4HC, generated by the addition of KI, is due to synergism.