Effect of Imidazoline Corrosion Inhibitors on Erosion/Corrosion Processes - an Electrochemical Investigation

Erosion-corrosion is a concern for oil and gas pipelines [1]–[3]. The simultaneous influence of fluid parameters such as velocity, turbulence, fluid regime and the characteristics of the corrosion scales formed on the pipe surface can accelerate erosion-corrosion inside oil and gas pipelines [4]. Corrosion inhibitors, made of imidazoline derivatives, are widely used in oil industry to prevent internal corrosion of pipelines. In this work, the influence of an imidazoline corrosion inhibitor on erosion-corrosion rates, in flowing fluid condition, is electrochemically investigated. The test electrolyte is synthesized to simulate condition of a multiphase gas pipeline. Electrochemical Impedance Spectroscopy (EIS) was used to measure the corrosion rate in presence of varying concentration of corrosion inhibitors. A cylindrical working electrode with a rotational speed of 1200 (rpm) was employed to simulate the dynamic behavior of the flowing fluid inside wet gas pipelines. The results revealed that corrosion inhibitor films could be readily removed from the steel surface by the erosional behavior of the flowing fluid if the adhesion factor of the surface films are not sufficient. This would expose the bare metal to the corrosive medium. The consequence of such phenomena is the lifespan reduction of pipelines and thus occurrence of immature erosion-corrosion failures. This study demonstrated that the adhesion force of the corrosion inhibitor films are directly related to the thickness of the formed film on the pipe surface and the shear stress generated by flow at the steel surface. References: [1] H. Mansoori, D. Mowla, F. Esmaeelzadeh, and A. H. Mohammadi, “Case Study: Production Benefits from Increasing C-Values,” OIL GAS J., vol. 111, no. 6, pp. 64–69, 2013. [2] H. Mansoori, R. Mirzaee, A. H. Mohammadi, and F. Esmaeelzadeh, “Acid Washes, Oxygenate Scavengers Work Against Gas Gathering Failures,” OIL GAS J., vol. 111, no. 7, pp. 106–111, 2013. [3] H. Mansoori, R. Mirzaee, F. Esmaeelzadeh, and D. Mowla, “Altering CP Criteria Part of Unified Anti-SCC Approach,” Oil Gas J., vol. 111, no. 12, pp. 88–93, 2013. [4] H. Mansoori, R. Mirzaee, F. Esmaeilzadeh, and et al., “Pitting corrosion failure analysis of a wet gas pipeline,” Eng. Fail. Anal., vol. 82, pp. 16–25, Dec. 2017.