Under-deposit corrosion of carbon steel is a major issue in many industries, leading to pipeline failure. In environments with low fluid flow rates, inert matter settles and accumulates on the bottom of pipelines, leading to localized corrosion. Large pit-like features can be detected under the deposits but limited understanding exists surrounding the use of chemical corrosion inhibitors in stifling their growth. In this study, a bespoke test setup has been used to evaluate the performance of different inhibitor chemistries in stifling the corrosion of deep pit-like features under thick (< 8 mm) inert deposit layers. Potentiodynamic
polarization and electrochemical impedance spectroscopy measurements were used to assess the corrosion profile of X65 carbon steel at recession depths of 0 mm and 9 mm in 2 wt.% NaCl brine, under CO2-saturated conditions, at 50 °C. Galvanic corrosion in the presence of corrosion inhibitors was measured via a zero-resistance ammeter. 2-mercaptoethanol was able to reduce corrosion rates in the presence of inert silicone dioxide deposit layers. In contrast, an imidazoline derivative was considerably less effective under the same conditions. Scanning electron microscopy was used for visual assessment of surface damage after 20 hours of corrosion.