Investigations of Localized Corrosion of Stainless Steel after Exposure to Supercritical CO_2

摘要

Severe localized corrosion of a 316 stainless steel autoclave occurred during investigating Type H Portland cement stability in 0.16 M CaCl_2 + 0.02 M MgCl_2 + 0.82 M NaCl brine in contact with supercritical CO_2 containing 4% O_2. The system operated at 85°C and pressure of 29 MPa. However, no corrosion was observed in the same type of autoclave being exposed to the same environment, containing Type H Portland cement cylindrical samples, also operating at pressure of 29 MPa but at 50°C. The operation time for the 85°C autoclave was 53 days (1272 hours) while that for the 50°C autoclave was 66 days (1584 hours). Debris were collected from the base of both autoclaves and analyzed by X-ray diffraction (XRD). Corrosion products were only found in the debris from the 85°C autoclave. The cement samples were analyzed before and after the exposure by X-ray florescence (XRF) methods. Optical microscopy was used to estimate an extent of the 316 stainless steel corrosion degradation.