Corrosion Reason Analysis of Flange for Flexible Pipe of a Certain Type of Vessel

Corrosion and leakage phenomenon occurred on a flange for flexible pipe in seawater pipeline of a certain ship. In order to find the corrosion and leakage reasons, chemical composition analysis and metallographic examination were conducted on the flange material, micro-morphology observation and energy spectrum analysis were carried out on the corrosion area. The results show that the zinc content in the leaky flange exceeded the standard. A large amount of zinc in the matrix was preferentially dissolved as an anode under seawater conditions, leaving a copper-rich matrix and forming a continuous micro-channel on the flange sealing surface. Seawater continued to infiltrate into and around, and eventually penetrated the entire sealing surface boss, resulting leakage.