Simulation of corrosion-erosion of passive metals using a micro-scale dynamical model

Abstract

This article reports our recent efforts in extending a micro-scale dynamical model (MSDM), which was originally developed to model mechanical wear, to simulation of erosion-corrosion or corrosive wear of passive metallic by taking into account of chemical and mechanical properties of passive films as well as the competition between passivation and failure of passive films during corrosive wear processes. In this model, the target material is discretized and mapped onto to a discrete lattice. Each lattice represents a small volume of the material. The site-site interaction is dependent on mechanical properties of the material. For erosion-corrosion involving solid particle impingement in corrosive slurry, each ejected solid particle is also discretized and treated in a similar way. Determined by the activity of the target metal, the lattice sites are classified into two groups: active and passive sites. During an erosion-corrosion process, passive lattice sites on surface, which protect the inner active lattice sites from being corroded, could be damaged or worn away by the impingement of ejected particles. When the passive sites on surface are removed and active lattice sites underneath are exposed to the corrosive solution, they begin to transform from an active state to a passive state, corresponding to the development of passive film. The active lattice sites continuously degrade until a complete passive film forms. The dissolution rate of the target metal is influenced by the passivation state and the deformation of the adjacent lattice regions. In order to evaluate the effectiveness of this model in simulating corrosive wear, erosion-corrosion of 304 stainless steel is simulated and preliminary comparison between modeling and experiments is made.