Abstract
This paper seeks to increase the understanding of under-deposit corrosion with sand and the development of better inhibitors to mitigate this type of corrosion under sweet (carbon dioxide) conditions. In these tests an electrode exposed to the bulk solution and an electrode under the sand were galvanically coupled. This method represents the under-deposit corrosion condition within oil and gas pipelines, mimicking how the pipe surface can be covered by solids such as sand. The corrosion rates of both electrodes were monitored simultaneously using the linear polarization resistance technique. Zero resistance ammetry was used to measure the coupling current between the electrodes underneath the sand and in the bulk solution. After injection of inhibitors, the under-deposit electrode acted as the local anode and a dramatic acceleration of its corrosion was observed. The linear polarization resistance corrosion rate, the potential of the coupled electrodes, and the galvanic current density before and after the injection of inhibitors were used to characterize the corrosion inhibitor performance. Factors that affect the under-deposit corrosion measurement, such as the sand thickness, inhibitor concentration and temperature, were investigated and utilized in order to assist in the future development of higher performing corrosion inhibitors for this environment.
