Effect of Si on the growth of Fe-Al intermetallic layer in Zn-11%Al-3%Mg coating

Pure iron specimens were immersed in Zn-11%Al-3%Mg-x%Si baths containing different amount of Si at 510 °C for different time. The effect of Si in Zn-11%Al-3%Mg bath on phase constitution and the growth of Fe-Al intermetallic layer in Zn-11%Al-3%Mg-x%Si coatings were investigated by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that the existence of Si in Zn-11%Al-3%Mg bath could affect the phase constitution of Fe-Al intermetallic layer and restrain remarkably the growth of the layer. The thickness of Fe-Al intermetallic layer is minimum when Si content in Zn-11%Al-3%Mg was 0.2 wt.%. The growth of Fe-Al intermetallic layer in Zn-11%Al-3%Mg and Zn-11%Al-3%Mg-0.2%Si coatings is controlled by diffusion mechanism. 0.2 wt.% Si in Zn-11%Al-3%Mg bath decreases obviously the growth-rate index n and the growth rate constant k of Fe-Al intermetallic layer in coating.