Corrosion Reason and Management Advice for Desalination Seawater Piping in a Certain Ship

Galvanized steel pipes were used for desalination seawater pipe in a certain type of ship. Galvanized steel pipe internal corrosion was serious and the water quality became bad after a period of time at sea. Through the corrosion morphology observasion and pitting depth measurement, the macroscopic corrosion morphology was observed; using the microscopic analysis methods such as fluorescence, IR and XRD, the corrosion products of galvanized pipe were analyzed. The results show that the galvanized pipe corrosion type is localized corrosion and pitting corrosion is serious. The main reasons for the galvanized pipe corrosion were as follows:firstly, corrosion of the seawater was rather strong and the water quality was in weak acid,secondly, unstable γ-FeOOH and Fe₃O₄ were main ingredients in the pipe, and rust layer was loose, which provide protection to the underlying substrate. It is suggested that for seawater pipeline replacement and maintenance in the late design, 316L stainless steel with stronger corrosion resistance should be chosen, and mineralization process should be carried out in desalination.