Phase-field modeling of pitting corrosion evolution in welded steel under the influence of residual stress

As the primary joining method, welding inevitably introduces residual stresses, which may accelerate localized pitting corrosion and thereby compromise structural durability and safety. To investigate the influence mechanism of welding residual stress on pitting corrosion evolution, this study develops a thermo-mechanical-electrochemical multiphysics-coupled phase-field model. First, a thermo-mechanical simulation of V-groove butt welding was conducted using a 6200 W moving heat source traveling at 1.0 m/min to generate the initial residual stress distribution. This field is then adopted as the initial mechanical state in the phase-field corrosion simulation. Subsequently, the effects of residual stress level, initial pit morphology, and multiple-pit coexistence on corrosion evolution are systematically investigated. The results show that tensile residual stress promotes pitting corrosion, exhibiting a threshold effect. When the residual stress exceeds 15% of the material’s yield strength, the corrosion depth increases by more than 40% compared to cases below this threshold. Under a static residual stress field, the corrosion morphology tends to become smoother. The initial defect geometry has a limited effect on the final corrosion damage. In the presence of multiple pits, the stress and ion concentration fields from adjacent pits overlap. It primarily promotes lateral expansion and area growth, with only a minor effect on vertical depth. The proposed phase-field framework reveals the underlying mechano-corrosive synergy between welding residual stresses and pitting corrosion. It thereby offers both a theoretical foundation and a numerical tool for assessing the long-term performance of welded steel structures in corrosive environments.