Anticorrosion performance of 1–benzylimidazole and synergistic iodide additives on C1018 carbon steel in 15% HCl solution

Acidizing, an industrial practice to enhance petroleum recovery, causes one of the most severe corrosion attacks on carbon steel drilling pipelines. Identifying highly efficient inhibitors to ameliorate this phenomenon is important for the petroleum industry. Here, the performance of 1–benzylimidazole (BZM) as a corrosion inhibitor for C1018 carbon steel in 15% HCl was investigated using electrochemical, weight loss and surface characterization techniques. Results from electrochemical techniques (electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), linear polarization resistance (LPR) and potentiodynamic polarization (PDP)) agree that BZM performs efficiently by providing inhibition efficiency up to 75% at 25 °C with 1200 ppm concentration. The addition of 5 mM KI significantly enhances BZM efficiency to 93% at 25 °C. BZM alone is a mixed–type corrosion inhibitor with slightly anodic behavior. The addition of KI transforms the BZM inhibition mechanism more cathodically. However, the BZM + KI efficiency decreases to 60% at 60 °C. Surface characterization by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirm that BZM uses its nitrogen and phenyl groups to adsorb on the steel surface, forming a thin film which mitigates localized corrosion.