Abstract: The water leakage was found on the shell ring surface of the reboiler during use. The reboiler has been installed and used for about one year. The leakage was located in the base metal area between the two welds on the shell ring. The shell ring and adjacent tube plate of the reboiler were both made of S30408 stainless steel, and the whole part was assembled by welding multiple components together. The macroscopic observations, component analyses, hardness tests, metallographic examinations, and energy-dispersive X-ray spectroscope analyses were conducted in the leakage area to find the fatigue cause. The results show that the leakage of the reboiler was caused by the corrosion cracks on the inner surface of the shell ring. The main reason for the cracks was the evaporation or splashing of water medium in the shell side of the reboiler, which caused the increase of the local surface Cl⁻ concentration in the small semi-circular area in the upper part of the shell side. Thus, the stress corrosion cracks formed under the action of the welding residual stress,.