Theoretical Investigation of the Interfacial Reactions during Hot-Dip Galvanizing of Steel

Abstract

In the modern galvanizing line, as soon as the steel strip enters the aluminum-containing zinc bath, two reactions occur at the strip and the liquid-zinc alloy interface: (1) iron rapidly dissolves from the strip surface, raising the iron concentration in the liquid phase at the strip-liquid interface; and (2) aluminum forms a stable aluminum-iron intermetallic compound layer at the strip-coating interface due to its greater affinity toward iron. The main objective of this study is to develop a simple and realistic mathematical model for better understanding of the kinetics of galvanizing reactions at the strip and the liquid-zinc alloy interface. In the present study, a model is proposed to simulate the effect of various process parameters on iron dissolution in the bath, as well as, aluminum-rich inhibition layer formation at the substrate-coating interface. The transient-temperature profile of the immersed strip is predicted based on conductive and convective heat-transfer mechanisms. The inhibition-layer thickness at the substrate-coating interface is predicted by assuming the cooling path of the immersed strip consists of a series of isothermal holds of infinitesimal time-step. The influence of galvanizing reaction is assessed by considering nucleation and growth mechanisms at each hold time, which is used to estimate the total effect of the immersion time on the formation mechanism of the inhibition layer. The irondissolution model is developed based on well established principles of diffusion taking into consideration the area fraction covered by the intermetallic on the strip surface during formation of the inhibition layer. The model can be effectively used to monitor the dross formation in the bath by optimizing the process parameters. Theoretical predictions are compared with the findings of other researchers. Simulated results are in good agreement with the theoretical and experimental observation carried out by other investigators.

Characterization of hot-dip galvanized coating on dual phase steels

“…First, because of the greater affinity of Al to iron than Zn, Fe-Zn brittle phase is suppressed, leading to the formation of a so called inhibition layer, an intermetallic compound of Fe-Al [1,2]. This is indispensable for a workable galvanized product [3,4]. Second, previous works reported that alloy elements in high strength steel, such as Al, Mn, Si, and Cr, will be selectively oxidized under a protective atmosphere of H 2 + N 2 plus trace amount of water vapor, leading to bare spot defects [5,6].…”

Structure-Mechanical Property Relationship in Hot-Dip Galvanized S355k2+N Steel Plates

“…The specific composition of the as-received S355K2+N steel plate (400x300x10 mm 3 ) and the zinc bath are respectively given in Table 1 and Table 2. The plate was cut in three sheet samples (350x100x10 mm 3 ).…”

“…The plate was cut in three sheet samples (350x100x10 mm 3 ). Two samples, A and B, were considered in order to be galvanized according to standard NF ENI ISO 1461, at 450°C with a holding time of 3 min for specimen A and 10 min for specimen B.…”

“…Most galvannealing research focuses on the identification of the chemical composition, the influence of the hold time [3], the alloying elements [4], the resistance of the coating to the corrosion or to the fatigue [5]. However, residual stresses, generated by Hot-dip Galvanizing treatment and their influence on mechanical behavior are seldom studied.…”

Effect of Fe 2 B orientation on erosion–corrosion behavior of Fe–3.5 wt.% B steel in flowing zinc

“…As the erosion time increases, the iron concentration reaches saturated state in the erosion layer, which results in the rapid interface corrosion reaction and the formation of large amounts of corrosion products. Previous studies also reported that the initial corrosion reaction proceeds very fast when the metal immerses into liquid metal [36][37][38]. The corrosion rate and the time can be estimated by the Eq.…”