This study investigated the effect of Al and Mg content and immersion time on the formation of periodic layered structure during hot-dip galvanizing in Al-Zn-Mg bath. The steel substrates were immersed in Al-Zn bath for 10 s to 120 s, with five levels of Al content in the range of 15 to 55 wt.%, and four levels of Mg additions, in the range of 0.5 to 3.0 wt.%. The microstructure and constituent phases of the periodic layered structure were characterized by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The coating with periodic layered structure contains a thin light gray Fe 2 Al 5 Zn x layer near substrate and outer periodic layered structure.The periodic layered structure consists of alternating light gray layer (FeAl 3 Zn x ) and black 2 gray layer (Al dendrites and Zn-rich interdendritic regions). The formation of periodic layered structure requires an incubation period t 1 , while if the immersion time is over t 2 , the periodic layered structure is destroyed. In addition, t 1 and t 2 varies with the Al content and Mg addition.

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