Kinetic and thermodynamic analysis of high-temperature CO2 corrosion of carbon steel in simulated geothermal NaCl fluids. (15th July 2020)

• Record Type: Journal Article
• Authors: Mundhenk, N.; Carrero, S.; Knauss, K.G.; Wonneberger, R.; Undisz, A.; Wu, Y.
• Is Part Of: Corrosion science. Volume 171(2020)
• Publication Date: 2020-07-15
• Subjects: CO2corrosion -- Carbon steel -- Thermodynamics -- Kinetics -- TEM; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.108597
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Kinetic and thermodynamic analysis of high-temperature CO2 corrosion. Electrochemical methods for corrosion rate determination at 80 °C, 160 °C and 240 °C. SEM, TEM, and XRD analyses of corrosion films reveal different growth mechanisms. At 160 °C and 240 °C Fex Oy offers superior corrosion protection compared to FeCO3 . At 80 °C high instantaneous corrosion rates are due to the absence of Fex Oy . Abstract: We discuss kinetic and thermodynamic aspects of carbon steel corrosion in CO2 -containing NaCl fluids up to 240 °C. Crystalline nm-thick Fe-oxide films only form at 160 °C and 240 °C providing instantaneous and moderate corrosion protection. The absence of Fe-oxide at 80 °C results in high initial corrosion rates until a moderately protective, but thick and porous, FeCO3 film forms. From the metal/film interface it grows inwards by replacing ferrite with FeCO3 . TEM reveals a precursory, likely hydrated and chloride-containing, phase that predates FeCO3 formation. Thermodynamic predictions agree well with experimental results in that Fe-oxide formation is favored over FeCO3 towards higher temperatures.