Time-dependent high-pressure CO2-induced corrosion and mechanical degradation in lightweight fly-ash cement/P110 steel system

This study innovatively investigated CO 2 -induced corrosion and mechanical degradation in lightweight fly-ash cement/P110 casing steel system under normal and high pressures. Key findings revealed time-dependent corrosion and mechanical evolution. Under normal pressure, cement properties peaked at 28 days, contrasting with 21 days under high pressure. Simultaneously, the corrosion rate of steel steadily increased, particularly under high pressure. A two-stage degradation process was proposed based on cement hydration and corrosion competition. Higher pressure accelerated degradation through intensified cement carbonation and cement/casing interfacial cracking. The predicted 30-year carbonation depth under high pressure was 51 mm based on the established fitting equation ( H = 3.7026 t 0.2919 − 4.8205 ).