Inhibition performance of imidazoline inhibitors for Q235-A steel in the simulated producing well water saturated with CO₂

Inhibition performance of three kinds of imidazoline derivative inhibitors for Q235-A steel in the simulated producing well water saturated with CO₂ at 85°C were studied using weight loss and electrochemistry techniques including electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results of weight loss showed that the three kinds of imidazoline derivative inhibitors all had good inhibitor properties at concentration of 40 mg/L, the inhibition efficiency of inhibitor HSJ-3 was up to 80%. The sharp decrease of anodic current density and positive shift of corrosion potential (E_corr) indicated that these imidazoline derivative inhibitors were all anodic inhibitors which worked as "negative catalysis". The results of EIS showed that the film of inhibitor HSJ-1 with alkyl formed slowly; the film of inhibitor HSJ-2 with thiourido group formed fast and could be auto-repaired; the film of inhibitor HSJ-3 with phosphonic group also formed fast, but decayed in a short time.