Immersion Time Dependence of the Reaction between Fe–Si Alloys and Liquid Zinc

Abstract

By use of Fe–0.10 and 0.97 mass%Si alloys, the immersion time dependence of the reaction between the Fe–Si alloys and liquid zinc has been studied for the time ranging from 60 s to 6 ks at various temperatures in the range from 713 K to 873 K. The relations between the thickness of the alloy layer (d) and the immersion time (t), and those between the quantity of iron having reacted with zinc (Δw) and the immersion time are obtained in the form of d=atm and Δw=btn, respectively, where a, m, b and n are constants.To obtain information on the silicon reactivity in hot dip galvanizing, the reactivity of the Fe–Si alloys with liquid zinc is compared with that of pure iron under the same condition used in this study. The reaction mechanism of the Fe–Si alloys with liquid zinc is discussed, by considering the morphology and growth of the alloy layer and the immersion time dependence of the quantity of iron having reacted with zinc.The rapid reaction of the Fe-0.10 mass%Si alloy with liquid zinc in the vicinity of 713 K and that of the Fe-0.97 mass%Si alloy in the vicinity of 753 K are caused by the effect of silicon that allows the formation of the (zeta+eta) mixture layer whose growth does not obey the diffusion-controlled process. The rapid reaction of the Fe-0.97 mass%Si alloy with liquid zinc in the vicinity of 793 K is caused by the effect of silicon on the rapid growth of the (delta 1+eta) layer.