Synergistic Corrosion Inhibition Effect of Oleic Acid Imidazoline and Oleic Acid in Saturated CO2 Salt Solution

The synergistic effect of imidazoline and oleic acid corrosion inhibitor on corrosion inhibition of N80 steel in formation water containing CO2 saturated oilfield was studied by weight loss method and electrochemical technology. The corrosion morphology was observed by SEM. By measuring the contact Angle of the metal surface film, the hydrophobic performance of the metal surface film was evaluated, and the adsorption model was established and the adsorption curve was fitted. The corrosion inhibition mechanism of the two corrosion inhibitors was analyzed when the two inhibitors acted alone and after mixing. The results showed that when imidazoline and oleic acid were used alone, the corrosion potential could be positively moved, and the inhibition efficiency was 82.89% and 78.51%, respectively, when the addition amount was 100 mg/L. When the imidazoline: oleic acid was 25∶75, the inhibition efficiency was the highest. Compared with the imidazoline with the same concentration alone, the inhibition efficiency was increased by about 15% (98.07%). When a single corrosion inhibitor was added, the corrosion degree of the metal surface decreased with the increase of the concentration. After the addition of the compound corrosion inhibitor, the number and the size of pitting decreased compared with the corrosion morphology after the addition of a single inhibitor at the same concentration. The contact angle of the metal surface increased after the combination of the two inhibitors, which indicated that the hydrophobic ability of the corrosion inhibitor film formed on the metal surface was stronger than that when the two inhibitors were used alone. The Gibbs free energy ΔG0 imidazoline and oleic acid were calculated as ‒48.578 kJ/mol and ‒48.319 kJ/mol, respectively. There is a good synergistic effect between imidazoline and oleic acid. A single imidazoline or oleic acid corrosion inhibitor acted on the metal surface through chemical adsorption. The corrosion inhibition mechanism after the combination of imidazoline and oleic acid could be attributed to the change of the structure of the mixed film which made the corrosion inhibitor film denser, thus achieving a better corrosion inhibition effect. © 2022, Chongqing Wujiu Periodicals Press. All rights reserved.