Corrosion inhibition behavior of rich in double bonds imidazolines in saturated CO₂ brine

Objective The linoleic acid imidazoline containing two double bounds was synthesized, and compared with the traditional oleic acid imidazoline containing a single double bond, the effect of its strcture on corrosion inhibition performance was studied.

Methods Q235 steel was immersed in a 3 wt% NaCl solution saturated with CO₂ at 60 ℃. Corrosion inhibition efficiency was evaluated through weight loss and electrochemical tests, and the morphological changes of the steel surface after corrosion were observed using surface analysis methods. The performance of synthesized corrosion inhibitor was also studied using theoretical calculations.

Results The results show that after adding 200 mg/L of the linoleic acid imidazoline containing two double bonds, the corrosion inhibition efficiency can reach 90%, which is superior to the commonly used oleic acid imidazoline. Structurally, the linoleic acid imidazoline only differs from the oleic acid imidazoline by the presence of one additional double bond. This extra double bond increases the adsorption sites of the imidazoline corrosion inhibitor, which makes it better adsorb to the metal surface.

Conclusions The linoleic acid imidazoline with two double bonds exhibits excellent corrosion inhibition performance on carbon steel and outperforms the oleic acid imidazoline under the same experimental conditions. The adsorption process conforms to the Langmuir adsorption isotherm, primarily adsorbing on the Fe surface through N—Fe bonding.