Synergistic effect of inhibitor mixture based on enhanced electron transfer

The inhibition performance of a mixture of an imidazoline quaternary ammonium salt (IM) and octylphenol polyoxyethene ether (OP) (IMO) toward carbon dioxide (CO₂) corrosion of L245 steel in 3 wt% sodium chloride (NaCl) solution at 25°C was studied using electrochemical measurements. Notably, the inhibition efficiency of the IMO inhibitor stayed steadily in the long-term immersion test, and the inhibition efficiency increased with time. This was attributed to the improved electron-transfer performance between the inhibitor molecules and the metal surface. OP molecules promoted electrons to the metal, while IM molecules accepted electrons from the metal. The interactions between the inhibitor molecules and metal surface were enhanced, and the relative bonding intensities were improved. Moreover, the adsorption configurations of the mixture of IM and OP facilitated the improvement of the thickness and the compactness of the inhibitor layer. OP and IM showed a good synergistic inhibition effect.