Use of Electrochemical Quartz Crystal Microbalance in the Study of FeCO3 Solubility (C2026-00011)

Kamila Turganova, Bruce Brown, David Young, Srdjan Nesic, Kushal Singla

Carbon dioxide (CO2) is commonly present in brine from oil and gas wells, creating conditions that trigger steel corrosion with accompanying formation of iron carbonate (FeCO3). FeCO3 present as a corrosion product layer can play a significant role in retarding corrosion, but it can also contribute to the development of localized attack under certain conditions. Before evaluating its protectiveness capabilities, it is important to establish the thermodynamic stability of FeCO3 under various environmental conditions.
In this study, an Electrochemical Quartz Crystal Microbalance (EQCM) was employed to experimentally determine the solubility of FeCO3 by monitoring in situ mass change on the surface, iron concentration, and pH changes in 1 wt.% NaCl solution sparged with CO2 at three different temperatures (60–80°C). Experimental results were compared to different solubility models: concentration and ionic strength based (Ma-OT model, 2021) and non-ideal solution speciation model (Pitzer model). The methodology developed in this study provides a basis for future investigation of FeCO3 solubility under different conditions, while the experimental findings provide a foundation for further research on FeCO3 precipitation, dissolution, and corrosion product layer protectiveness.