TY - JOUR A1 - Aristia, Gabriela A1 - Le, Quynh Hoa A1 - Bäßler, Ralph T1 - Corrosion of Carbon Steel in Artificial Geothermal Brine: Influence of Carbon Dioxide at 70 °C and 150 °C JF - Materials N2 - This study focuses on the corrosion mechanism of carbon steel exposed to an artificial geothermal brine influenced by carbon dioxide (CO2) gas. The tested brine simulates a geothermal source in Sibayak, Indonesia, containing 1500 mg/L of Cl-, 20 mg/L of SO4 2-, and 15 mg/L of HCO3-with pH 4. To reveal the temperature effect on the corrosion behavior of carbon steel, exposure and electrochemical tests were carried out at 70 °C and 150 °C. Surface analysis of corroded specimens showed localized corrosion at both temperatures, despite the formation of corrosion products on the surface. After 7 days at 150 °C, SEM images showed the formation of an adherent, dense, and crystalline FeCO3 layer. Whereas at 70 °C, the corrosion products consisted of chukanovite (Fe2(OH)2CO3) and siderite (FeCO3), which are less dense and less protective than that at 150 °C. Control experiments under Ar-environment were used to investigate the corrosive effect of CO2. Free corrosion potential (Ecorr) and electrochemical impedance spectroscopy (EIS) confirm that at both temperatures, the corrosive effect of CO2 was more significant compared to that measured in the Ar-containing solution. In terms of temperature effect, carbon steel remained active at 70 °C, while at 150 °C, it became passive due to the FeCO3 formation. These results suggest that carbon steel is more susceptible to corrosion at the near ground surface of a geothermal well, whereas at a deeper well with a higher temperature, there is a possible risk of scaling (FeCO3 layer). A longer exposure test at 150 °C with a stagnant solution for 28 days, however, showed the unstable FeCO3 layer and therefore a deeper localized corrosion compared to that of seven-day exposed specimens. KW - Carbon steel KW - CO2 KW - Corrosion KW - Electrochemical impedance spectroscopy KW - Geothermal PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-498168 DO - https://doi.org/10.3390/ma12223801 SN - 1996-1944 VL - 12 IS - 22 SP - 3801-1 EP - 20 PB - MDPI CY - Basel AN - OPUS4-49816 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Le, Quynh Hoa A1 - Bäßler, Ralph A1 - Bettge, Dirk T1 - On the corrosion mechanism of CO2 transport pipeline steel caused by condensate: Synergistic effects of NO2 and SO2 JF - Materials N2 - To study the effects of condensed acid liquid, hereafter referred to as condensate, on the CO2 transport pipeline steels, gas mixtures containing a varying concentration of H2O, O2, NO2, and SO2, were proposed and resulted in the condensate containing H2SO4 and HNO3 with the pH ranging from 0.5 to 2.5. By exposing the pipeline steel to the synthetic condensate with different concentration of acidic components, the corrosion kinetic is significantly changed. Reaction kinetic was studied using electrochemical methods coupled with water analysis and compared with surface analysis (scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometry (XRD)) of corroded coupons. The results showed that, although the condensation of NO2 in the form of HNO3 causes faster general corrosion rate, it is the condensation of SO2 in the form of H2SO4 or the combination of SO2 and NO2 that may cause much more severe problems in the form of localized and pitting corrosions. The resulting corrosion forms were depended on the chemical nature of acids and their concentration at the same investigated pH. The effects of changing CO2 flow rate and renewing condensate on pitting corrosion were further studied. KW - Carbon capture, utilization and storage technology KW - CCUS KW - Corrosion KW - Condensate KW - Electrochemical characterisation KW - Pitting corrosion KW - Impurities KW - Carbon steel PY - 2019 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-473685 UR - https://www.mdpi.com/1996-1944/12/3/364 DO - https://doi.org/10.3390/ma12030364 SN - 1996-1944 VL - 12 IS - 3 SP - 364, 1 EP - 17 PB - MDPI CY - Basel AN - OPUS4-47368 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -