Abstract
Most metals naturally corrode in an engineering environment and form corrosion products. The corrosion products can be either soluble or insoluble in the aqueous solution. The insoluble corrosion products (ICP) could have profound effects on the corrosion kinetics of the concerned metal. In this study, a multi-phase-field formulation is proposed to investigate the effects of ICP formation on pitting corrosion kinetics. The Gibbs free energy of the metal-electrolyte-insoluble corrosion product system consists of chemical, gradient, and electromigration free energy. The model is validated with experimental results and several representative cases are presented, including the effect of the porosity of ICP, under-deposit corrosion, corrosion of sensitized alloys, and microstructure-dependent pitting corrosion. It is observed that corrosion rate and pit morphology significantly depend on ICP and its porosity for the same applied potential.
Highlights
Corrosion is a material degradation process that is difficult to avoid because most metallic materials have practical applications in corrosive environments
Pitting corrosion of a metal is usually considered to go through three major stages: pit nucleation, pit growth, and re-passivation through formation of insoluble corrosion products (ICPs)
A multi-phasefield (MPF) model is developed for the prediction of pitting corrosion kinetics with ICP formation
Summary
Corrosion is a material degradation process that is difficult to avoid because most metallic materials have practical applications in corrosive environments. Tsuyuki et al.[23] proposed a PF model that incorporates the pH effect on corrosion rate by considering pH-dependent interface mobility, where pH is approximated for each case by Corrosion Analyzer software Their model qualitatively describes the overall phenomenon quite well but lacks any validation with experimental results, as identified by the authors. To the best of our knowledge, no PF model in the literature explicitly considers the formation of ICP as a new phase, or studies its is possible to add cathodic reactions when cathode becomes rate-limiting electrode This addition is straightforward and has been detailed in the Appendix C of our previous work.[29] The MPF model formulation is detailed in the Methods section. Because the molar concentration of metal ions close to the interface is well below the saturation limit, as shown
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