Three-dimensional numerical simulation of micro-galvanic corrosion in 304 stainless steel weld microstructures

This study proposes a novel three-dimensional galvanic corrosion finite element simulation model that incorporates the morphological characteristics of δ-ferrite, with experimentally characterized weld microstructures as the core input parameters. During the simulation, the Nernst-Planck equation was employed to characterize the migration behavior of chloride ions in saturated saline solution and the electrochemical reaction characteristics within the system. Combined with the Arbitrary Lagrangian-Eulerian method, dynamic tracking of the evolution process of galvanic corrosion at the weld surface and cross-sectional scales was realized. Simultaneously, continuous immersion corrosion experiments were conducted, and the corrosion morphologies were observed via Laser Scanning Confocal Microscopy (LSCM) and Scanning Electron Microscopy (SEM), achieving deep coupling between experimental and simulation methods. The results show that the established model can accurately characterize the spatial evolution characteristics of weld galvanic corrosion. Specifically, continuous lath and skeletal ferrite tend to form penetrating corrosion channels, causing through-thickness damage to the weld, while dot-line and discontinuous reticular ferrite can physically block the corrosion channels and confine corrosion to the shallow surface layer of the weld. This confirms that the ferrite distribution pattern exerts a significant regulatory effect on the penetrating galvanic corrosion damage of welds at the electrochemical level. The proposed ‘microstructure distribution-potential difference-corrosion channel’ coupled calculation framework exhibits good universality, providing a systematic reference system for the numerical simulation of electrochemical corrosion of metal components. • Experimental microstructure was integrated into the computational model of micro-galvanic corrosion. • Immersion corrosion tests verified ferrite’s preferential corrosion behavior in 304 stainless steel welds. • Continuous ferrite forms corrosion channels, while discontinuous ferrite blocks corrosion propagation.