Abstract: Corrosion inhibition of three imidazoline derivates with different numbers of benzene rings, namely 2-phenyl-1-ethylamino imidazoline(CI-1), 2-phenyl-1-ethylamino-1-methylbenzyl quaternary imidazoline(CI-12) and 2-phenyl-1-benzoyl ethylamino imidazoline(CI-13), on mild steel in CO₂-saturated brine solution was evaluated by mass-loss method and potentiodynamic polarization method. The results show that the three imidazoline derivates can inhibit CO₂ corrosion effectively with CI-12 ranking the highest. They mainly restrain the anodic dissolution and act as anodic-type inhibitors. The adsorptions of these derivates on the mild steel surface follow the Langmuir adsorption isothermal equation and belong to chemical adsorption.

Key words: Corrosion inhibitor, CO₂ corrosion, Langmuir adsorption, Imidazoline derivate