A small addition of Al in the liquid Znbath inhibits the Fe/Zn reactions during hot dipgalvanizing of steel sheets. Although it is wellknown that Al and Fe are tied up in an layerlocated at the interface between Fe and Zn, theeffect of the galvanizing parameters on theformation of this Alrich interfacial layer is not.This study has been carried out to determine theeffect of the galvanizing parameters on theformation of this Al-rich layer. Five zinc bathscontaining 0.10,0.12,0.13,0.16, and 0.18 wt pct Alwere used to produce galvanized coatings ofcommercial ultra-low-carbon(ULC) steel substrate.Full inhibition of the Fe/Zn reactions wasachieved in baths with Al content above 0.15 wtpct. The Al-rich layer is isomorphous to Fe2Al5crystals and the Fe-Al ratio is close to Fe2Al5with large amounts of Zn present (22 to 28 wt pct).The morphology of the Al-rich layer is stronglyrelated to the Al content of the bath. Indeed,bath contents above 0.15 wt pct are associatedwith two sublayers of Fe2Al5 crystals, making upcolonies of grains of similar crystallographicorientation and directly associated to thecrystallographic orientation of the steel grains.In baths with contents below 0.15 wt pct, the Al-rich layer has only one sublayer of crystals andshows colonies of grains with similar orientation.Finally, the Fe2Al5 crystals have a strongcrystallographic texture. X-ray diffraction (XRD)reveals that the (200) planes are parallel to the surface of the substrate.
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