Preparation and Corrosion Inhibition of a Mixed Acid Imidazoline Anti-Sulfur Corrosion Inhibitor

A mixed acid imidazoline anti-sulfur inhibitor was prepared using sebacic acid, oleic acid and diethylenetriamine as raw materials. The effects of mass ratio of oleic acid to sebacic acid, molar ratio of carboxylic acid group to diethylenetriamine, cyclization temperature and cyclization time on the corrosion inhibition were investigated by orthogonal test to determine the optimal synthesis process of mixed acid imidazoline anti-sulfur corrosion inhibitor. The effect of dosage of mixed acid imidazoline anti-sulfur inhibitor synthesized through the optimal process on corrosion inhibition was studied by immersion test and electrochemical test. The results showed that the optimum synthetic conditions were that the mass ratio of oleic acid to sebacic acid was 4:1, the molar ratio of carboxylic group to diethylenetriamine was 1:3, the cyclization temperature was 220℃, and the cyclization time was 5 h. The mixed acid imidazoline anti-sulfur corrosion inhibitor synthesized in the optimum conditions was a mixed type corrosion inhibitor and could reduce the corrosion rate for N80 steel from 1.23 mm/a to 0.073 mm/a, and its inhibition efficiency was up to 99.5%.