Numerical Analysis Model of Galvanic Corrosion with Ion Movement and Reactions

Numerical analysis models for galvanic corrosion have been developed in recent years, but most of the ordinary models can simulate only current density and potential distribution in an electrolyte solution. In order to make clear corrosion mechanism, more information such as pH, ion and corrosion product distributions are necessary. However, it is difficult to compute these phenomena by mathematical model because various kinds of ions and complex reactions exist in corrosion progress. Calculating ion movement with satisfying electroneutrality is especially difficult.We have developed a new numerical analysis model for galvanic corrosion that can calculate ions movement and reactions. In this model, ion density distribution is corrected by solving Poisson's equation to satisfy electroneutrality. Reactions are calculated based on chemical equilibrium.Galvanic corrosion of a model Fe/Zn couple in a NaCl solution was calculated with this model. The difference of ion and corrosion product distributions in 50 ppm and 50000 ppm NaCl solutions was discussed. Corrosion product distribution obtained by this numerical analysis model agreed well with OH distribution of corrosion product measured by FT-IR method qualitatively.