Modeling Electric-Potential for a Crack Subjected to Corrosion Under Static and Cyclic Loading

Abstract

High strength steels are increasingly being used in applications such as ship hulls and oil and gas pipelines which are subjected to corrosive environment. These steel grades exhibit more than an order of magnitude higher crack growth rates in corrosive environments compared with the crack growth rates in air. A mathematical model is developed based on the slip dissolution mechanism to evaluate the chemistry and potential distributions in the occluded crack. The species distribution due to diffusion and ion migration is evaluated by considering the effect of ferrous hydroxide formation on the transport properties in the electrolyte. It is also found that the potential and pH drop in the crack is affected by the crack tip stress and strain fields. The dissolution of iron at the crack tip is enhanced by the pH drop. Both steady state and transient numerical studies are carried out to determine the evolving crack geometry. Thus, by considering reactions inside the crack, a better representation of the species and potential distributions can be obtained.