The comparatively little research on sherardizing focuses on pack cementation , , , ,  and . In most of these studies the zinc powder contains a halide activator (NH4Cl, ZnCl2). This activator is reported to facilitate the zinc deposition on the steel substrate by chemical vapor deposition . This mechanism is similar to the deposition of aluminum on iron- or nickel-based materials during pack aluminizing , ,  and . In other works  and  it PR-957 is stated that the Fe–Zn layer formation during sherardizing is mediated by the vapor pressure of zinc itself without addition of any halide activators. However, Schmitz et al.  reported an increase in layer thickness when a certain amount of ZnCl2 is added to the sherardizing process.
The aim of the present work is to investigate the impact of various zinc halides (ZnX2 with X∈ Cl, Br, I ) on the formation of Fe–Zn phases on steel substrate. For photosynthesis purpose we anneal steel samples in zinc powder in sealed quartz glass ampoules. On one hand experiments are carried out in pack cementation without any additives. On the other hand we performed sherardizing under rotation with ZnX2 added to the zinc powder. We report the impact of the zinc halides on the composition of the interdiffusion layer and on the growth kinetics of the individual Fe–Zn phases. The growth kinetics are compared to those obtained by sherardizing in pack cementation. Finite difference methods (FDM) were applied to simulate the growth of the Fe–Zn phases and to explain their growth kinetics.