Part I. Thermodynamic and kinetic aspects of the hot DIP (Zn) - Coating formation

Abstract

A hot dip (Zn) - coating formation is carried out in the industry conditions. Two types of the steel substrate are applied to the experiment. Two morphologically different coatings are obtained, accordingly. A hot dip (Zn) - coating formation is also carried out in the laboratory conditions for making some additional explanations of the revealed phenomena. The thickening of the Γ - phase sub-layer is observed in details to determine time of the transition from stable into meta-stable solidification. The Fe-Zn phase diagrams for stable and meta-stable equilibrium are calculated, respectively. The phase diagram for dissolution is also determined. The criterion of the higher temperature of the solid/liquid (s/1) interface is successfully applied to the Fe-Zn system to justify the competition between stable and meta-stable solidification. The mass balance verification is performed for the (Zn) - coating in order to define the nominal Zn - solute concentration required by dissolution and next by solidification. The Zn - solute concentration in the dissolution, super-saturation and saturation zones are determined thermodynamically. The growth kinetics is described for all the sub-layers in the (Zn) - coating.