The effects of Cl− and Ca2+ on corrosion and scale formation of 3Cr steel in CO2 flooding produced fluid

Abstract

To elucidate the effects of Cl⁻ and Ca²⁺ on the corrosion and scale formation of 3Cr steel in CO₂ flooding-produced fluid, corrosion weight loss experiments, and titration experiments were conducted. The resulting products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). This study examined the corrosion and scaling behavior of 3Cr steel under the influence of Cl⁻ and Ca²⁺. The results indicate that both Cl⁻ and Ca²⁺ promote the corrosion of 3Cr steel. Notably, Cl⁻ diminishes the promoting effect of Ca²⁺ on corrosion and inhibits scaling, revealing a mutual enhancement between corrosion and scaling. The mechanisms of localized corrosion under varying concentrations of Cl⁻ and Ca²⁺ differ; under-scale corrosion occurs in environments with 5000 mg·L⁻¹ Cl⁻, while Cl⁻induced corrosion is observed in 20000 mg·L⁻¹ Cl⁻ environments. This study highlights that under the synergistic effects of Cl⁻, Ca²⁺, and scaling processes, the protective product film dissolves, thereby influencing both corrosion and scaling processes.