Abstract: A tin bronze globe valve for seawater pipeline of a ship leaked after being used for a period of time. The causes of leakage were analyzed by means of macroscopic observation, chemical composition analysis, scanning electron microscopy and energy spectrum analysis, metallographic examination and so on. The results show that the chemical composition of the cast tin bronze material met the technical requirements of the relevant standards, and no obvious abnormality was found in the microstructure. Local corrosion occurred on the sealing surface, and seawater erosion corrosion was the main cause of local corrosion on the sealing surface. The presence of casting porosity in the material will promoted the occurrence of corrosion, and the valve seal was not tightly sealed, resulting in leakage.