Experimental Study on the Crack Sensitivity of Storage Tank Bottom Plate Welded Joints in Hydrogen Sulfide Environments

This study investigates the cracking problems observed on the surface of T-joint welds and shell welds of storage tanks used for storing crude oil containing trace amounts of hydrogen sulfide (H2S) in a certain oilfield. Tests were conducted on Q235 and Q345R welded joints using electrodes with different hydrogen contents to evaluate their susceptibility to cold cracking, hydrogen-induced cracking (HIC), and sulfide stress corrosion cracking (SSC), as well as the effects of post-weld hydrogen removal treatment. The results show that no delayed cold cracks occurred in any welded joints of either Q235 or Q345R. Both materials exhibited hydrogen-induced cracking (HIC) on the cross-section, and the hydrogen removal treatment had little effect on improving HIC resistance. The overall HIC sensitivities of Q235 and Q345R were similar, both showing susceptibility to hydrogen absorption and internal cracking in the wet H2S environment. In contrast, SSC tests revealed that low-hydrogen welds exhibited no fractures or cracks, whereas high-hydrogen welds developed surface cracks. After hydrogen removal treatment, no SSC cracks were found in any specimens, regardless of electrode type. Therefore, for storage tanks operating in H2S-containing environments, the combination of low-hydrogen electrodes and post-weld hydrogen removal treatment is recommended to improve weld reliability and ensure operational safety.