The effect of Zn coating layers on the hydrogen embrittlement of hot-dip galvanized twinning-induced plasticity steel

•Hot-dip galvanized TWIP steel underwent premature failure due to the brittle ζ layer.•H was trapped at the η-Zn layer and the Fe-Zn intermetallic layers of ζ and δ.•The amount of detrapped H was great in an order of the ζ, δ and η-Zn layers.•δ and ζ layers had higher activation energies of H detrapping than grain boundaries.•H-charging of galvanized TWIP steel did not degrade the tensile properties.

The effect of Zn coating layers on hydrogen embrittlement (HE) was investigated using hot-dip galvanized (HDG) twinning-induced plasticity (TWIP) steel. The Zn coating layers consisted of an η-Zn layer and Fe-Zn intermetallic layers of ζ and δ without Γ. H was trapped particularly at the ζ layer without Zn-H compounds. The activation energies of H desorption from the δ and ζ layers were 60.0 kJ mol−1 and 75.4 kJ mol−1, respectively. The H-charged HDG_TWIP steel did not reveal HE due to the intermetallic layers, which are exceptionally brittle even when H is not enriched.

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