The nature of the intermetallic layer which forms on the steel surface during immersionin typical galvanizing baths for galvannealed (GA) sheets production has been investigatedon two commercial Titanium-stabilized Interstitial-Free (Ti-IF) steel substratesgalvanized in baths with different Al contents. Results from this study show that in bothcases the inhibition layer is biphasic and composed of a very thin Al-rich phase layer,identified as Fe2Al5Znx, and a thicker Zn-rich phase layeron top of it, identified as δ. Experimental results also show that theFe2Al5Znx phase layer becomes discontinuouswhen decreasing the bath Al content. Discussions about the mechanisms of formation and thefinal microstructure of this inhibiting layer are also tackled in this paper by means ofthe Al-Fe-Zn ternary phase diagram at 460 °C and assumptions to justify any deviation fromthermodynamic equilibrium are as well proposed.
