Experimental study on the influence of CO2 corrosion on hydrogen permeation and hydrogen embrittlement sensitivity of X52 pipeline steel

• Providing detailed experimental data on the hydrogen permeation behavior of X52 steel under different corrosion conditions. • Elucidating the mechanisms by which CO 2 corrosion products influence hydrogen embrittlement sensitivity. • Offering practical guidance for the evaluation and management of hydrogen-blended natural gas pipelines . The corrosion product layer formed on the inner wall of hydrogen-blended natural gas pipelines significantly affects the interaction between hydrogen and pipeline steel, thereby influencing the hydrogen diffusion characteristics and hydrogen compatibility of the pipeline steel. By combining in-situ gaseous hydrogen permeation tests, SSRT tests, SEM morphological analysis, and XRD testing, this study investigates the microscopic morphology, composition, and structural characteristics of the CO 2 corrosion products formed on X52 pipeline steel under different conditions. It quantifies the impact of the CO 2 corrosion product layer on the hydrogen permeation kinetics of X52 steel and elucidates the mechanism of mechanical property degradation of X52 steel in a gaseous hydrogen environment with a CO 2 corrosion product layer, revealing the essential role of the corrosion product layer in affecting material hydrogen compatibility. The results show that compared with uncorroded samples, the steady-state current density of X52 steel samples under different corrosion conditions is significantly reduced. Furthermore, the hydrogen embrittlement index calculated from the SSRT tests and the fracture morphology indicate that while corrosion exacerbates the loss of material ductility, it also hinders hydrogen permeation.