Imidazole Derivative as Novel Effective Inhibitor of Mild Steel Corrosion in Aqueous Sulphuric Acid

Abstract

Corrosion behavior of mild steel immersed in 0.5 M H2SO4 and corrosion inhibition in the presence of different concentrations of 2,4-di-tert-butyl-6-(1h-phenantro[9,10-d]imidazol-2-yl) phenol (PIP) was investigated using weight loss and hydrogen evolution techniques at 303 – 333 K. The results indicate a maximum inhibition efficiency of 68.45% in the presence of 10 x 10-5 M PIP at 303 K. The inhibitory action of PIP in the acid solution is best described by Temkin adsorption isotherm. The Arrhenius and transition state equations are used to calculate activation parameters and the mechanism of physical adsorption is proposed for PIP from the values of Ea and ΔG*ads obtained. Thermodynamic studies indicate that the adsorption of PIP to the metal surface is spontaneous. Quantum chemical calculations using DFT is used to calculate some electronic properties of the molecule in order to ascertain any correlation between the inhibitive effect and molecular structure of the molecule PIP. PIP protected the mild steel against corrosion in the acid medium at the studied temperatures by virtue of adsorption. The corrosion rate increased with temperature both in the absence and presence of the inhibitor, but the increase was lesser in the presence of the inhibitor compared to that of the free acid solution. The inhibition efficiency increased with increase in concentration of the inhibitors.