Abstract: A certain company's shell and tube heat exchanger experienced severe leakage within less than 2 months of operation, with multiple holes and cracks appearing in the bellow. The section of the leaking bellow was intercepted on site, and the alloy composition, microstructure, and corrosion product characteristics of the bellow were analyzed using morphology observation, chemical composition analysis, metallographic examination, and energy spectrum analysis. Based on the comprehensive information of the service environment and material characteristics, the cause of the leakage was analyzed and discussed. The results indicated that the leakage of the bellow originated from the inner wall of the pipe, and the excessive inclusion in the pipe tissue was the main reason for the weakening of the corrosion resistance of the bellow, inducing pitting corrosion, and ultimately perforation.