An Extended Finite Element Method Based Approach for Modeling Crevice and Pitting Corrosion

Abstract

A sharp-interface numerical approach is developed for modeling the electrochemical environment in crevices and pits due to galvanic corrosion in aqueous media. The concentration of chemical species and the electrical potential in the crevice or pit solution environment is established using the steady state Nernst–Planck equations along with the assumption of local electroneutrality (LEN). The metal-electrolyte interface fluxes are defined in terms of the cathodic and anodic current densities using Butler–Volmer kinetics. The extended finite element method (XFEM) is employed to discretize the nondimensionalized governing equations of the model and a level set function is used to describe the interface morphology independent of the underlying finite element mesh. Benchmark numerical studies simulating intergranular crevice corrosion in idealized aluminum–magnesium (Al–Mg) alloy microstructures in two dimensions are presented. Simulation results indicate that corrosive dissolution of magnesium is accompanied by an increase in the pH and chloride concentration of the crevice solution environment, which is qualitatively consistent with experimental observations. Even for low current densities the model predicted pH is high enough to cause passivation, which may not be physically accurate; however, this model limitation could be overcome by including the hydrolysis reactions that potentially decrease the pH of the crevice solution environment. Finally, a mesh convergence study is performed to establish the accuracy of the XFEM and a sensitivity study examining the relationship between crevice geometry and species concentrations is presented to demonstrate the robustness of the XFEM formulation in handling complex corrosion interface morphologies.

A phase field formulation for dissolution-driven stress corrosion cracking

“…Capturing the complex morphologies resulting from this three-stage process is not an easy task and typically requires defining moving interfacial boundary conditions and manually adjusting the interface topology with arbitrary criteria when merging or division occurs. Numerical methods have been developed to capture the moving boundary problem of localised corrosion; these include the eXtended Finite Element Method (X-FEM) (Duddu et al, 2016), Arbitrary Lagrangian-Eulerian (ALE) techniques (Sun et al, 2014) and peridynamics (Chen and Bobaru, 2015). However, progress is often limited by the inability to deal with arbitrary 3D geometries, cumbersome implementations or the computational cost.…”

Modeling the effect of insoluble corrosion products on pitting corrosion kinetics of metals

“…Because these models ignore the effect of electromigration, they cannot capture a smooth transition from reaction-to diffusion-controlled regimes. Some notable numerical models that do incorporate the effects of electromigration are Laycock and White's 16 FEM model, the Sun et al 17 Arbitrary Lagrangian-Eulerian (ALE) model, and Duddu's 18 XFEM model. More recently, diffuse interface models, namely phase field (PF) models, for localized corrosion have been proposed, which incorporate the electromigration effect and thus have the ability to capture reaction-, migration-, and diffusion-controlled regimes.…”

A level set model for stress‐dependent corrosion pit propagation

“…Different methods can be found in literature to model stable corrosion pit propagation. These are finite volume models, 7,8 models that use the finite element method combined with adaptive meshing, [9][10][11] models using the extended finite element method (XFEM) combined with the level set method, [12][13][14] phase field models, [15][16][17][18] peridynamic models, 19 and cellular automata (CA) models. 20,21 Only two of these models considered lacy cover formation.…”