Reduction of the emissions of CO2 and other greenhouse gases is a global challenge. Carbon capture and storage (CCS) is one of the most ready to use technologies applicable for industries such as biogas upgrading, cement, and in general, gas cleaning. Even though the technology is mature, optimization is still needed to reduce costly production losses and shutdowns. CO2 corrosion is a significant problem in the industry, and therefore, fundamental information regarding the corrosion product, FeCO3, is needed. FeCO3 creates a protective barrier on the steel surface under the right conditions, and therefore information on the solubility is important. In this study, the solubility of FeCO3 in water and under the influence of CO2 is investigated. Results revealed that the FeCO3 solubility in water (with and without the presence of CO2) is constant with temperature. A global maximum in the FeCO3 solubility was seen when increasing CO2 pressure. This phenomenon is not seen in the typical carbonate systems.