Effects of Mn addition on the microstructure and indentation creep behavior of the hot dip Zn coating

• Mn addition could significantly refine the grain of the Zn coating.
• Twins could be observed in the Zn coatings.
• The stress exponent of the Zn coating increases with Mn addition.
• The creep process of the Zn coating is dominated by dislocation climb and twins.

The Zn coatings with different Mn additions were prepared by hot dip process, and the effects of the Mn addition on the microstructure and indentation creep behavior of the coatings were investigated through scanning electron microscope and constant-load holding indentation technique at the room temperature. Some twins can be observed in the microstructure of Zn coating, which may account for the formation of the large thermal misfit stress between the zinc coating and the steel substrate. The amount of twin microstructure in the Zn coating decreases with the Mn addition. It is also found that Mn addition could induce MnZn13 phases to precipitate along the grain boundary and significantly refine the grains of Zn coatings. The steady-state stress of the Zn coating could be improved by Mn addition. The creep stress exponent values are in the range of 14–46 and increases with Mn addition. The creep process of the Zn coating is dominated by dislocation climb and twin formation.