Numerical Investigation of Galvanic Corrosion Behaviour in Ship Shafting Systems Considering Rotational Hydrodynamic Coupling Effects

Galvanic corrosion in shafting systems, which are composed of dissimilar metallic components such as propellers, shafts, and stern structures, poses a significant threat to the structural integrity and operational reliability of ships. Conventional prediction methods typically rely on static electrochemical assumptions and neglect the rotational hydrodynamic conditions generated by the operation of the propeller, potentially leading to substantial underestimation of the corrosion risk in real operating environments. This study presents a coupled numerical modelling framework in which electrochemical potential field analysis is integrated with rotational-flow-induced mass transfer effects to evaluate galvanic corrosion behaviour in ship shafting systems. The electrochemical potential distribution in seawater is solved using a boundary element method, while the hydrodynamic flow fields obtained from computational fluid dynamics simulations are incorporated by applying velocity-dependent limiting diffusion current density corrections to cathodic polarisation relations.

A representative stern-shaft assembly consisting of a nickel–aluminium bronze propeller, stainless steel shaft, and carbon steel stern structure is analysed under both static and multiple rotational operating conditions. The results show that propeller-induced turbulent flow significantly enhances oxygen transport to cathodic surfaces, leading to increased galvanic current densities and localised corrosion intensification, particularly near the shaft–propeller junction. Under high-speed operating conditions, the corrosion current density in critical regions increases by approximately 92–150% compared with static predictions. The modelling approach proposed here provides a realistic prediction tool for corrosion risk assessment, and offers engineering guidance for cathodic protection design, material selection, and maintenance planning of marine propulsion shafting systems.