某燃气-蒸汽联合循环机组余热锅炉中压蒸发器鳍片管在运行期间发生泄漏，采用宏观形貌和显微组织观察、扫描电镜及能谱分析、物相分析及实验室溶垢试验等方法对其失效原因进行了分析。结果表明：泄漏管漏点位置及附近腐蚀产物层下组织均无异常；个别鳍片管局部区域在原始制造时已发生严重腐蚀，形成了鼓疱状腐蚀产物，其无法通过化学酸洗溶解去除而遗留下来，在机组运行期间，该位置进一步遭受氧腐蚀而发生减薄，最终导致泄漏；建议加强中压蒸发器鳍片管的入场验收管理，重点关注鼓疱状腐蚀、划伤等原始缺陷，以防止此类泄漏事故再次发生。

A fin tube of middle pressure evaporator for heat recovery steam generator of gas-steam combined cycle unit leaked during operation. Macroscopic appearance and microstructure observation, scanning electron microscope and energy spectrum analysis, phase analysis and laboratory scale dissolving test were used to analyze the leakage reasons. The results show that the structures under the leakage point and nearby corrosion product layer were normal. Local areas of some fin tubes had been severely corroded during the original manufacturing, forming the blister-like corrosion products, which cannot be removed by chemical pickling and dissolution. During the unit operation, the position was further corroded by oxygen and thinned, which eventually led to the leakage. It was suggested to strengthen the acceptance management of the fin tube of middle pressure evaporator, focusing on the original defects such as blister-like corrosion and scratches to prevent such leakage accidents from recurring.