Effect of hydrophilic group on inhibition behaviour of imidazoline for CO 2 corrosion of N80 in 3%NaCl solution

Four kinds of imidazoline inhibitors with different hydrophilic group, i.e. carboxymertyl imidazoline (CMI-11), hydroxyethyl imidazoline (HEI-11), aminoethyl imidazoline (AEI-11) and imidazoline (IM-11) had been synthesised and characterised by infrared and ultraviolet spectra. The inhibition performance of these imidazoline inhibitors for CO₂ corrosion of N80 in 3%NaCl solution was investigated through linear polarisation resistance, polarisation curve and electrochemical impedance spectroscopy. In order to study the relationship between the molecular structure and inhibition properties of these imidazoline inhibitors, quantum chemical calculations have been also applied. The results showed that the presence of a hydrophilic group was beneficial to the corrosion inhibition properties of these imidazoline inhibitors, and the inhibition efficiency follows the order: CMI-11>HEI-11>AEI-11>IM-11. The calculated quantum chemical parameters supported that the lower the lowest unoccupied and highest occupied molecular orbital energy gap, the higher the inhibition efficiency. The theoretical calculation was in good agreement with experimental results.