An ab initio molecular dynamics study was used to investigate the effects of Ag and Ni additives on Zn diffusion in steel hot-dip galvanizing. Ag-Zn, Ni-Zn, and Zn-Zn ensembles were selected to model the industry process. For the Zn-Zn ensemble, the calculated pair correlation function, first peak position, and coordination number were in good agreement with available experimental data. Differences in the structural and electronic properties among Ag-Zn, Ni-Zn, and Zn-Zn ensembles were examined. For Zn self-diffusion, a diffusion constant of 2.48 x 10-9m2/s was obtained; very close to the experimental value of 2.37 x 10-9m2/s. The Zn diffusion constants of different ensembles increased in the order: Ag-Zn ≈ Zn-Zn > Ni-Zn, which was in agreement with the additive effects upon the thickness of coatings in galvanizing, where Ag increased the coating thickness, but Ni decreased it. The molecular dynamics simulations revealed that the role of additives in controlling the zinc coating thickness was to alter zinc diffusion speed before reaching the substrate.

Effects of Ag and Ni Additives on Zn Diffusion in Steel Hot-Dip Galvanizing: an ab initio Molecular Dynamics Simulation. Zhu, W., Wu, P., Jin, H.M., Liu, H.L.: Chemistry of Materials, 2004, 16[26], 5567-73