Abstract: A rubber fuel tank was found to be leaking after installation and was found to be caused by cracking of the fuel tank flange. Macroscopic inspection of the cracking position of the flange, macro and micro observation of the fracture, material composition analysis, bonding interface analysis, metallographic examination, and the Fourier Transform Infrared (FT-IR) spectroscopy analysis were carried out to analyze the cracking reasons of the flange and the corrosion reasons of metal embedded in the flange. The results show that the cracking mode is overload. The main reason for the overload cracking is that the bonding edges of the embedded metal of the flange and the rubber were completely corroded by the chlorohydrin rubber, causing the bonding interface to crack, which in turn decreased the load-bearing capacity of the structure. There were a large number of microcracks at the edge of the metal in the flange, which further aggravated the weakening of the bonding region.