A systematic study is presented to determine the corrosion behavior of four different steels (X65 carbon steel, 1Cr, 5Cr and 13Cr) that could be considered as pipeline/tubular materials for the transport and/or injection of supercritical CO2 for carbon capture and storage (CCS) applications. The purpose of the research was to establish the influence of material selection on the critical water content required to avoid substantial levels of internal corrosion in an impure supercritical CO2 system containing sulphur dioxide (SO2) and oxygen (O2). Experiments were performed in autoclaves containing supercritical CO2 at 8 MPa and 35°C in the presence of 100 ppm (mole) SO2 with 20 or 1000 ppm O2 under varying levels of humidity from 0 to 100%. General corrosion rates for all four materials were determined over a period of 48 hours via gravimetric analysis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy were all implemented to assist in identifying surface corrosion products. Results from under-saturated experiments indicated that 13Cr steel enables a greater critical water content to be tolerated before corrosion occurs in the presence of 100 ppm SO2 and 20/1000 ppm O2. No corrosion attack was observed at a water content of 650 ppm for 13Cr, while X65, 1Cr and 5Cr produced general corrosion rates of ~0.01 mm/year. At water contents of 1200 ppm, corrosion rates for all materials remained below 0.05 mm/year in the presence of 100 ppm SO2 and 20 ppm O2, with 13Cr again exhibiting superior corrosion resistance. Increasing O2 content to 1000 ppm had no significant effect on corrosion rates in under-saturated conditions. In water-saturated conditions at 100 ppm SO2/20 ppm O2 X65, 1Cr and 5Cr produced dramatically higher corrosion rates in the range of 0.7-0.8mm/year, whilst 13Cr maintained a low corrosion rate below 0.02 mm/year. Changing O2 content to 1000 ppm in water-saturated conditions increased the corrosion rates of X65, 1Cr and 5Cr to ~0.9-1.1 mm/year and that of 13Cr to 0.65mm/year, indicating the material corrosion sensitivity to O2 content. Comparison with previous results by the same authors indicated a noticeable synergy between SO2 and O2 which resulted in a greater degradation rate being observed compared to the sum of individual corrosion rates when SO2 and O2 were present independently at their respective concentrations in the water-saturated system. The research highlights that one option for controlling the corrosion rate under these specific impure supercritical CO2 conditions may be through the implementation of 13Cr, although this may impose a significant cost penalty compared to carbon steels. The work shows that low Cr-bearing steels were unable to mitigate the effects of corrosion compared to X65 steel in these particular water-saturated conditions.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)