Corrosion caused by carbon dioxide (CO2) on carbon steel pipes and oil and gas processing-equipment is common. Water-soluble CO2 produces carbonic acid (H2CO3) which has more corrosive properties than hydrochloric acid (HCL) at the same pH. Electrochemical impedance spectroscopy and linear polarization resistance were employed to determine the processes occurring during the adsorbed inhibition process on the metal surface. Imidazoline based inhibitor concentration variations helped uncover the ability of inhibitor inhibition and the passivation strength of the formed layer. This research was conducted on A106 Grade. B carbon steel in an environment of 3 % NaCl. The imidazoline based inhibitor concentration varies from 0 to 40?ppm at 40 ?. At a temperature of 40 ? and without inhibitor, the corrosion rate showed 143.6 MPY, but dropped drastically to 22.4 MPY when 5?ppm inhibitor was added. Electrochemical Impedance Spectroscopy was applied to study the inhibition mechanism. It was found that based on an adsorption isotherm analysis, chemisorption happened between inhibitor and metal.