Electrochemical System to Study Corrosion of Metals in Supercritical CO2 Fluids

The CO₂ sequestration is an important technology to be promptly developed if fossil fuels are continued to be used and CO₂ emission to atmosphere is to be reduced. Low alloy carbon steel pipelines are considered to be used to transport the supercritical CO₂ from power plants to underground sequestration sites. However, the CO₂ stream will not be pure and dry, but will contain a number of corrosive contaminants. We have developed an experimental system that allows employing a number of in-situ electrochemical techniques, such as Electrochemical Impedance Spectroscopy, Linear Sweep Voltammetry, and Cyclic Voltammetry, at elevated temperature and pressure. These methods are used to measure the parameters of the real time corrosion process without withdrawing the sample from the system. Traditional weight loss/gain analysis and ex-situ methods of imaging and surface analysis - optical microscopy, SEM, TEM, and XRD, are used in parallel to investigate the surface degradation. The results of our first measurements of corrosion  of API 5L carbon steel in supercritical CO₂ fluids doped with H₂O, O₂, and SO₂ at temperatures up to 50 ºC and pressures up to 150 bar are presented in this paper.