Caracterisation de revetements galvanises, d'aciers haute resistance (French text)

In the past few years, we have seen a growing interest in research on the inhibition layer of galvanized steel. The inhibition layer is the result of a reaction between the aluminum contained in the liquid zinc bath and the iron in steel during the first moments of galvanization. Researchers observed that this layer slowed down or inhibited the formation of the intermetallic compounds Fe-Zn by reducing the interdiffusion Fe-Zn (Jordan & Marder, 1998). Despite the importance of this inhibition phenomenon and the results from research on the subject, the composition of the layer is not yet fully understood.; Although many authors have observed that the inhibition layer consisted mainly of Fe2Al5 containing a certain percentage of zinc (Uchida et al., 1998; Komatsu et al., 1998; Nakamori et al., 1996; Guttman et al., 1995), some studies have revealed the presence of FeAl3 (Lin et al., 1995; McDevitt et al., 1997) or of the compound FexAlyZnz (Urenicek et al., 1973; Tang et al., 1994).; The present study focuses on the characterization of the inhibition layer (its nature and morphology). In order to determine its exact chemical composition, a method was developed by using various characterization tools (transmission electron microscopy, scanning electron microscopy using a field emission gun, x-ray spectroscopy) and preparation tools (focused ion beam). We were able to determine the chemical composition of the inhibition layer for seven shades of galvanized steel at the Centre de Recherche et Développement de Cockerill-Sambre.; In addition, a dissolution technique developed by Baril (2000) allowed the observation of the layer enriched in aluminum (planar view).; Finally, we examined the effect of an agitation system for a galvanization simulator by comparing a galvanized steel by three different means: industrially, in the laboratory and in laboratory with agitation. (Abstract shortened by UMI.)...