Electrochemical Investigation of the Influence of an Amine-Based Corrosion Inhibitor on Corrosion -Erosion of Gas Pipelines

Mohammad Rasti, Ali Mobaraki Nejad

Gas pipelines are exposed to erosion-corrosion phenomena in production fields. The synergetic effect of fluid parameters (such as velocity, turbulence, fluid regime, etc.) and the characteristics of the corrosion scales formed on the pipe wall can accelerate erosion-corrosion inside oil and gas pipelines. Most of times, injection of corrosion inhibitors (CI) is the only available option to prevent internal corrosion of pipelines. In this study, the influence of an amine-based CI on erosion-corrosion rates, in flowing fluid condition, is electrochemically investigated. The test electrolyte is synthesized to simulate condition of a multiphase gas pipeline. The corrosion rate is measured by Electrochemical Impedance Spectroscopy (EIS) in presence of different concentration of corrosion inhibitor (0, 5, 50, 100 ppm). The dynamic properties of the flowing fluid inside gas pipelines is simulated by means of a cylindrical working electrode with 1200 (rpm) rotational speed. The results showed that in the lack of good adhesion of the corrosion inhibitor films, they could be readily detached form the steel surface by the erosional characteristics of the flowing fluid, exposing the bare metal to corrosive media. This dramatically reduces the life span of the pipeline and causes immature erosion-corrosion failures. 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.