An inspection in a ship revealed severe corrosion happened in the BFe30-1-1 cupronickel heat exchange tubes of the auxiliary condenser. After performing eddy current testing on these tubes, areas with significant corrosion were selected for further examination. Macro observation, chemical composition analysis, energy dispersive spectroscopy (EDS), and Raman spectroscopy were used to examine the corrosion areas and to analyze the causes of corrosion. The experimental results indicated that the chemical composition and microstructure of the tube met the relevant requirements.The incomplete removal of oil films during production led to the formation of residual carbon films during heat treatment, which in turn triggered electrochemical corrosion, ultimately becoming the primary factor for the extensive corrosion of the cupronickel tubes. Additionally, residual water stains in corrosion pits was also an important cause of the accelerated corrosion in the cupronickel tubes.