Kinetic and thermodynamic analysis of high-temperature CO2 corrosion of carbon steel in simulated geothermal NaCl fluids

Abstract

We discuss kinetic and thermodynamic aspects of carbon steel corrosion in CO 2 -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, FeCO 3 film forms. From the metal/film interface it grows inwards by replacing ferrite with FeCO 3 . TEM reveals a precursory, likely hydrated and chloride-containing, phase that predates FeCO 3 formation. Thermodynamic predictions agree well with experimental results in that Fe-oxide formation is favored over FeCO 3 towards higher temperatures.

Study of a Local Structure at the Interface between Corrosion Films and Carbon Steel Surface in Undersaturated CO2 Environments

“…Previously, it has been suggested that FeCl + is a precursor phase originating from a homogeneous distribution of Cl − at the interface analyzed on cross sections by SEM during a dissolution process. 19 In addition, a mixture of subsets of interatomic distances from the structures for α-Fe, Fe 3 C, and FeCl 2 was quantified. These subsets of interatomic distances, including Fe 3 C and α-Fe, provide evidence for the structural damage at the interface in the beginning of the reaction.…”

“…Cementite (Fe 3 C) is also frequently mentioned to be present as an undissolved phase after the dissolution of α-Fe from steel to form the FeCO 3 corrosion film. ,− The resulting Fe 3 C phase consists of a porous network that either is in close contact or is intermingled with the FeCO 3 corrosion film. Various authors suggest that Fe 3 C increases corrosion rates because of its ability to form a galvanic connection with α-Fe, promoting local acidification. ,− Despite all these observations, other works have suggested a beneficial role of Fe 3 C as inductors of the “protective” FeCO 3 formation through the solubilization of α-Fe (Fe 2+ release) to form FeCO 3 .…”

Effect of Corrosion Temperature on the Corrosion of Q235 Steel and 16Mn Steel in Sodium Aluminate Solutions

“…15 Mundhenk et al testified that Fe-oxide formation is favored over FeCO 3 with moderately protective, thick, and porous characteristics toward higher temperatures. 16 Nimmervoll et al revealed that the mass loss increased with rising temperature, and a model of the course of corrosion was proposed. 17 Adewumi et al demonstrated that the corrosion rate increased as the exposure temperature, and uniform corrosion was noted on the specimens exposed to a low temperature (25 °C), while pitting corrosion was noted on those exposed to elevated temperature (55 °C).…”

“…The research results of Aydin et al show that the open-circuit potential value of SnO 2 -coated mild steel shifted toward more positive values compared to uncoated mild steel even under high elevated temperatures . Mundhenk et al testified that Fe-oxide formation is favored over FeCO 3 with moderately protective, thick, and porous characteristics toward higher temperatures . Nimmervoll et al revealed that the mass loss increased with rising temperature, and a model of the course of corrosion was proposed .…”

Revealing the temperature effects on the corrosion behaviour of 2205 duplex stainless steel from passivation to activation in a CO2-containing geothermal environment

“…Geothermal production fluids normally contain significant amounts of CO2 in the range of 1-2.5% by weight [20] . CO2 corrosion ("sweet corrosion") has been discussed extensively by many authors in the oil and gas field under low temperatures and low pressures [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] . High CO2 pressure accelerates the corrosion processes by lower pH and introducing significant amounts of substances (e.g., H2CO3, HCO3 -).…”