Inhibition of mild steel corrosion by hexadecylpyridinium bromide in 0.5 M H2SO4

The inhibiting action of hexadecylpyridinium bromide (HDPB) on mild steel in 0.5 M H2SO4 solution in the temperature range of 30–60 °C was studied using potentiodynamic technique and weight loss measurements. The collected polarization curves were used to study the effects of the inhibitor concentration and temperature on the corrosion behavior of mild steel. The inhibitor was found to be a mixed-type inhibitor. Maximum range of protection efficiency of HDPB was obtained at its critical micelle concentration (cmc). Weight loss measurements confirmed the above results. The inhibitor showed stronger influence on the anodic branch by shifting the free corrosion potential to more positive values. The surface coverage values were found to fit with Bockris–Swinkels isotherm with molecular ratio equal to 3. The apparent activation energy of corrosion, Ea is lower in presence than in absence of the inhibitor. Also, higher negative values of the free energy of adsorption, ΔGadso and higher positive value of the enthalpy of adsorption, ΔHadso were obtained. The above results helped us to predict the mode and extent of adsorption of HDPB on the iron surface.