Nature of the inhibition layer in GA baths

Abstract

-The nature of the intermetallic layer which forms on the steel surface during immersion in typical galvanizing baths for galvannealed (GA) sheets production has been investigated on two commercial Titanium-stabilized Interstitial-Free (Ti-IF) steel substrates galvanized in baths with different Al contents. Results from this study show that in both cases the inhibition layer is biphasic and composed of a very thin Al-rich phase layer, identified as Fe 2 Al 5 Zn x , and a thicker Zn-rich phase layer on top of it, identified as δ. Experimental results also show that the Fe 2 Al 5 Zn x phase layer becomes discontinuous when decreasing the bath Al content. Discussions about the mechanisms of formation and the final microstructure of this inhibiting layer are also tackled in this paper by means of the Al-Fe-Zn ternary phase diagram at 460 • C and assumptions to justify any deviation from thermodynamic equilibrium are as well proposed.

Roles of Al and Mg on the Microstructure and Corrosion Resistance of Zn-Al-Mg Hot-Dipped Coated Steel

“…Normally, a small amount of Al (0.1-3 at.%) is introduced to the molten bath during the galvanization process. This results in the formation of an intermetallic film between the zinc coating and the steel substrate, which helps prevent the formation of Fe-Zn intermetallic phase or "outbursts" that could negatively impact the mechanical properties of the final coating [8][9][10]. Dou in an HCl solution.…”

Operando kinetics of hydrogen evolution and elemental dissolution I: The dissolution of galvanized steel in hydrochloric acid

“…The use of a galvanized steel coating as a reference material also demonstrates the sensitivity of the AESEC technique to nanometric films. During the galvanization process with a molten 0.1 -1 at.% Al-Zn bath, an intermetallic film is formed between the zinc coating and the steel substrate, presumably in the form of Fe 2 Al 5 Zn x (0 < x < 1) [16][17][18][19][20]. This film, on the order of 20 -50 nm, inhibits the formation of Fe-Zn intermetallic phase or -outbursts‖ that are detrimental to the mechanical properties of the final coating.…”

Operando Kinetics of Hydrogen Evolution and Elemental Dissolution I: The Dissolution of Galvanized Steel in Hydrochloric Acid

“…The use of a galvanized steel coating as a reference material also demonstrates the sensitivity of the AESEC technique to nanometric films. During the galvanization process with a molten 0.1 -1 at.% Al-Zn bath, an intermetallic film is formed between the zinc coating and the steel substrate, presumably in the form of Fe 2 Al 5 Zn x (0 < x < 1) [16][17][18][19][20]. This film, on the order of 20 -50 nm, inhibits the formation of Fe-Zn intermetallic phase or -outbursts‖ that are detrimental to the mechanical properties of the final coating.…”