The mass loss method, electrochemical tests, scanning electron microscopy morphology analysis, and molecular dynamics simulation were used to study the synergistic mechanism of imidazoline (IM) and thiourea (TU) on ASTM A106B steel in CO2-saturated NaCl solution. The experimental results clearly revealed that IM and TU had good synergistic corrosion inhibition effect, and the combination of 5 mg/L IM and 5 mg/L TU exhibited the highest inhibition efficiency of 95.1%. Inhibitor molecules replaced the water molecules originally adsorbed on the metal surface and led to inhibition effects. The adsorption of the inhibitor mixtures had a better inhibition effect than individual inhibitors. The adsorption configuration and inhibition performance of the inhibitors demonstrated that the TU molecules first adsorbed on the metal surface to form the first layer, and then the IM adsorbed on TU to form the second layer. The number of water molecules originally adsorbed on the Fe surface decreased, and the diffusion of water molecules in the inhibitor film slowed down, thereby having a synergistic inhibition effect on metal corrosion.

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