Experimental study on mechanical properties of rock salt under hydrogen corrosion

With the growing demand for large-scale hydrogen energy storage, salt caverns have attracted considerable attention as an efficient and secure storage approach. Owing to its high reactivity and diffusivity, hydrogen may interact with the surrounding rock in salt caverns, potentially affecting the safety and stability of salt cavern hydrogen storage. However, the evolution of the mechanical properties of rock salt under hydrogen corrosion remains insufficiently understood. To investigate the effects of hydrogen corrosion on the mechanical properties of rock salt, mechanical tests were performed on rock salt and interlayer samples subjected to hydrogen corrosion for 0, 30, and 60 d, complemented by microstructural characterization using computed tomography (CT) and scanning electron microscopy (SEM). The results show that: (1) The mechanical response to hydrogen corrosion varies with lithology. After 60 d, the uniaxial compressive strength of rock salt decreases by 3.9%, while that of the interlayer increases by 14.5%; (2) Confining pressure mitigates the weakening effect of hydrogen corrosion. After 60 d, the triaxial compressive strength of rock salt decreases by 1.6%, 1.0%, and 1.6% under confining pressures of 5, 10, and 15 MPa, respectively; (3) Hydrogen corrosion significantly reduces the tensile strength of both rock salt and interlayers. After 60 d of corrosion, the tensile strength of rock salt decreases by 26.2%, while that of the interlayer decreases by 51.1%; (4) Hydrogen corrosion slightly deteriorates the shear strength of rock salt under different normal loads. After 60 d, the shear strength of rock salt decreases by 10.6%, 2.6%, and 5.0% under normal loads of 10, 20, and 30 kN, respectively. Microstructural analyses reveal that these macroscopic mechanical changes are governed by the synergistic effects of grain boundary weakening, mineral phase transformation, and microcrack propagation. This study provides quantitative references for the engineering design of salt cavern hydrogen storage and offers a scientific basis for assessing its safety and stability. It is recommended that engineering designs explicitly account for the significant reduction in the tensile strength of the surrounding rock due to hydrogen corrosion, avoid tensile stress concentration zones, and prioritize salt formations with low impurities.