Diffusion driven grain boundary migration in iron during zincification

The Grain-Boundary Diffusion of Zn in α-Fe

“…Also, it has been suggested that grain-boundary migration rates may be limited by the transport of Zn vapor to the Fe surface and not by diffusion in the grain boundaries. [6] Further, the Zn sources in these studies did not maintain a constant Zn vapor pressure with time, and therefore the boundary conditions in these studies could be changing.…”

“…[2] Despite the large use of galvanized steel products, the reaction of molten Zn with solid Fe is not fully understood. Several previous studies [3][4][5][6] have shown that at temperatures from 300 to 620°C, Zn diffuses rapidly into Fe. Some authors have called this ''anomalously fast'' diffusion of Zn in Fe.…”

“…[3] Several of the diffusion studies have used thin Fe foils ð$ 100 lm thick) with Zn vapor sources. [4][5][6] In the thin-foil studies, grain-boundary migration often occurs that obscures diffusion results. Also, it has been suggested that grain-boundary migration rates may be limited by the transport of Zn vapor to the Fe surface and not by diffusion in the grain boundaries.…”

General vapour-phase galvanizing and duplex coatings

“…Schmitz et al reported even lower rates at lower temperature [35]. Yu and Shewmon were unable to produce a coating above 550°C [34]. On the other hand, Short and Mackowiak, as well as Reumont et al, obtained different thickness of coatings depending on surface orientation at 500°C; and some places have even not reacted at all after 6 hours [30,33].…”

“…Bretez et al, as well as Reumont et al, have qualitatively studied the reactivity of low carbon steels (with various concentrations of silicon) with zinc vapour at 500°C, showing that the intermetallic compound changed at the surface with the temperature of growth [32,33]. Additionally, the study of Yu and Shewmon on pure iron and ultra-low carbon steel has revealed that the out-diffusion of iron between 550°C and 600°C produced hillocks of the Γ phase on the surface at the top of grain boundaries [34]. Symmetrically, zinc diffused downwards along grain boundaries.…”