THE EFFECT OF THIADIAZOLE RING FORMATION ON MILD STEEL CORROSION IN ACIDIC MEDIA: THEORETICAL AND ELECTROCHEMICAL STUDIES

The influence of isophthalohydrazide (IPH), 5,5′ -(1,3-Phenylene)bis(N-ethyl-1,3,4-thiadiazol-2-amine) (IBET) and 5,5′ -(1,3-Phenylene)bis( N-ethyl-1,3,4-thiadiazol-2-amine)(PBETA), were tested as corrosion inhibitors for carbon steel in 1 M HCl solution. The corrosion inhibition efficiency was measured by using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The inhibition efficiency was found to increase with increasing inhibitor concentration up to maximum 95.6% at 30°C. The inhibition efficiencies obtained from these methods were in good agreement. The Langmuir adsorption isotherm was found to provide the best explanation of the adsorption behavior of the investigated inhibitors on the metal surface. The calculated adsorption thermodynamic parameters reveal a between chemi- and physisorption of the inhibitors on the metal surface. Quantum chemical calculations study were further applied to reveal effect of geometric and electronic structural parameters on the inhibition efficiency of inhibitors (%IE). The morphology of carbon steel samples was investigated by scanning electron microscopy (SEM).