By means of combined processes the range of zinc alloy coatings which may be produced using conventional hot-dip or electrolytic deposition can be significantly extended. In this article, two basic processes will be described: on the one hand the conventional hot-dip or electrolytic deposition followed by deposition of an additional metallic coating and subsequent diffusion-annealing. On the other hand metallic pre-coating followed by hot-dipping or electrolytic deposition and subsequent diffusion-annealing.By applying additional thin Mg, Mn or Fe-coatings with a thickness in the order of 100-500 nm on hot-dip or electro-galvanised steel sheet by means of PVD and subsequent thermal processing promising applications result, since Zn-Mg, Zn-Mn or Zn-Fe alloy coatings with favourable microstructures, corrosion and application-related properties are obtained.Zn-Ni or Zn-Ni-Fe alloy coatings may be obtained by electrolytic deposition of a Ni pre-coating (0.5-2#mu#m) and subsequent galvannealing of such a steel strip. Furthermore, the use of pre-coatings is an interesting approach to improve the hot-dip galvanisability of high-strength steels.
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