Development of Numerical Calculation Method of Formation of Corrosion Products in Galvanic Corrosion

A numerical calculation method was developed for obtaining the corrosion product chemical distribution in galvanic corrosion of a zinc-coated iron substrate under atmospheric conditions. A one-dimensional (1D) model, in which the width of the solution was mathematically divided into minute elements, while the solution height (<i>h</i>^sol) perpendicular to the substrate surface was treated as a non-geometric variable, was applied to the developed calculation method. It was confirmed that time step could be larger when corrosion product formation was calculated based on Gibbs free energy changes of the reactions. The developed calculation method was validated by the qualitative agreements between measured and calculated results. In the measured and the calculated results, it was confirmed that the potential difference between Zn and Fe was larger and the corrosion products formed in lower Cl^- concentration in stability diagram were formed in the lower NaCl concentration solutions. Since the developed calculation method is suitable for the calculations in which <i>h</i>^sol is thin and is variable and corrosion period is long, it is suitable for the calculations of atmospheric corrosion.