INVESTIGATION OF LOW-ALLOY STEEL DEGRADATION UNDER COMBINED CARBON DIOXIDE CORROSION AND ABRASIVE WEAR CONDITIONS

This paper presents the results of an experimental study on the synergistic effect under the combined action of CO2 corrosion and abrasive wear on low-alloy steel 09G2S, commonly used in oil and gas pipelines. The study was conducted using a specialized flow-loop test bench simulating real operational conditions, including flow velocity (up to 5 m/s), CO2 concentration (1.2 g/L) and abrasive particles (SiO2 sand, 4.2 g/L). The material degradation rates were evaluated using gravimetric and electrochemical (LPR) methods. The results demonstrated that under the combined action of corrosion and erosion, the total mass loss (4.7634 mm/year) significantly exceeded the sum of individual corrosion (1.7495 mm/year) and erosion (1.6821 mm/year) losses, confirming the presence of the synergistic effect. The calculated synergy coefficient (2.8671 mm/year) and factor contribution analysis revealed dominant synergistic interaction (60% of total degradation), while pure erosion and corrosion accounted for 27% and 13%, respectively. The ΔCR/ΔER ratio of 0.117 (according to ASTM G119−09) corresponds to the equality of synergistic and additive effects with a shift towards synergy. The obtained data are of practical importance for predicting pipeline service life and developing protection methods against corrosion-erosion wear. The proposed methodology combines field-representative conditions with high measurement accuracy.