The influence of a sulfonated acrylic terpolymer scale inhibitor on CO2 corrosion behavior of N80 steel in simulated produced water

In this paper, a sulfonated acrylic terpolymer (SAS/AA/AMPS) scale inhibitor were synthesized and employed as scale inhibitors to investigate their effects on the CO2 corrosion behavior of N80 steel in simulated produced water under high-temperature and high-pressure conditions. The corrosion and scaling inhibition performance was evaluated using weight loss measurements and in-situ electrochemical techniques. The morphology, composition, and structure of the corrosion product layers formed under varying scale inhibitor concentrations were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and synchrotron-based computed laminographic (SRCL). The results demonstrated that the scale inhibitor significantly influenced the formation and properties of the corrosion product layers on the metal surface. At low concentrations, the scale inhibitor suppressed initial CaCO3 scaling, promoted Fe2+ release, and induced partial substitution of Fe2+ by Ca2+ in FeCO3, resulting in lattice distortion, reduced layer protectiveness, and accelerated early-stage corrosion. Meanwhile, at higher concentrations, the formation of a dense FexCayCO3 composite layer was observed, which significantly enhanced the long-term corrosion resistance of the steel. SRCL analysis revealed that the composite corrosion product layer formed at 100 mg/L exhibited lower porosity and higher density, contributing to superior protective properties. Furthermore, a mechanistic model was proposed to elucidate the relationship between scale inhibitor concentration, corrosion product layer formation, and the resulting corrosion inhibition performance, providing insights into optimizing scale and corrosion control strategies in CO2-saturated environments.