Mechanisms and kinetics of the inhibition layer breakdown in the case of Ti IF steel grades galvanized in GA baths

Mécanismes et cinétiques de la rupture d'inhibition dans le cas d'un acier IF Ti galvanisé dans un bain GA

D. Zapico Álvarez (1) , Florence Bertrand (1) , J.-M. Mataigne (1) , M.-L. Giorgi (2)

1 ArcelorMittal Maizières Research SA
2 LGPM - Laboratoire de Génie des Procédés et Matériaux - EA 4038

A reaction mechanism is proposed accounting for the inhibition layer breakdown in the case of Ti IF steels. This mechanism can be summarized in two steps: 1) the transformation of the bi-layered inhibition layer into a mono-layered one, made of the δ (FeZn7) phase only, as a result of the Zn enrichment at the steel/inhibition layer interface, and 2) the local nucleation of the Г (Fe3Zn10) phase at the steel grain boundaries, breaking the δ layer off, when the Zn concentration at these locations becomes high enough (outburst formation). The kinetics of this reaction strongly depends on the Ti IF steel chemistry. The effect of the steel chemical composition on the inhibition layer breakdown kinetics would be ruled by the rate of Zn diffusion at the steel grain boundaries and the ability of the steel to accumulate the Zn atoms within a critical volume for the nucleation of Г phase at these locations.

Mots clés: inhibition layer; inhibition breakdown; Al-Fe-Zn ternary system; interfacial reactions; galvannealing

Domaines: Matériaux

D. Zapico Álvarez, Florence Bertrand, J.-M. Mataigne, M.-L. Giorgi. Mechanisms and kinetics of the inhibition layer breakdown in the case of Ti IF steel grades galvanized in GA baths. Galvatech 2015, May 2013, Toronto, Canada. ⟨hal-01810021⟩