Synergistic Effect Between Oleic Imidazoline and 2-Mercaptobenzimidazole for Increasing the Corrosion Inhibition Performance in Carbon Steel Samples

In this work, the corrosion rate and inhibition efficiency of oleic imidazoline and 2-mercaptobenzimidazole in 1 M HCl were studied on carbon steel samples. The corrosion efficiency of oleic imidazoline and 2-mercaptobenzimidazole at a concentration of 75 ppm was 85.8 and 82.9%, respectively. In addition, a mixture of these reagents at a ratio of 1:1 showed enhanced corrosion inhibition. The optimal concentration of the proposed mixture of reagents was 75 ppm. In this case, the inhibition efficiency was 97.8% (by weight loss method). The synergistic inhibition effect between the components of the proposed mixture was obtained 15.9%. Meanwhile, by increasing the temperature from 298.15 to 373.15 K, the corrosion inhibition of the reagents was not considerably decreased, which was associated with their complete adsorption on the surface of the carbon steel samples. The adsorption of inhibitors followed the Langmuir isotherm. The values of free energy of adsorption in the presence of the corrosion inhibitors ranged from -31.6 to -32.62 KJ/mol, which indicated both physisorption and chemisorption features. Moreover, the results of electrochemical impedance spectroscopy and potentiodynamic polarization tests confirmed that the mixture of reagents at the ratio of 1:1 has a significantly higher inhibitory ability compared to each of the reagents alone. The used reagents behaved as a mixed-type inhibitor and affected both cathodic and anodic reactions.