The failure of a condensing copper tube in a steam turbine's condenser in a particular plant is used as an example in this paper, and the causes of the copper tube leakage are investigated using a combination of macro-inspection, scanning electron microscopy, corrosion product analysis, and other techniques. The findings showed that after prolonged operation, the copper produced scaling phenomena on the inner wall and created a significant number of corrosion pits beneath the scale, which ultimately led to perforated leaking. The dezincification corrosion mentioned in GB/T 30579–2022 “Damage Modes Identification for Pressure Equipments” on cooling water corrosion is not to blame for the corrosion and leaks, which are directly related to the Cl element in the circulating water.