Effect of Si content on wettability of dual phase high strength steels by liquid Zn-0.23 wt.%Al

The wettability of dual phase steels by liquid Zn-0.23 wt.%Al at 450 °C (723 K) was investigated using the dispensed sessile drop method. Dual phase steels of six different Si contents (0 wt.%, 0.12 wt.%, 0.18 wt.%, 0.3 wt.%, 0.5 wt.%, and 1.0 wt.%) annealed in a 15 %H₂-N₂ gas atmosphere at a dew point of-60 °C (213 K) were examined. As the Si content increased from 0 wt.% to 0.5 wt.%, the wettability worsened. However, as the Si content increased to 1.0 wt.%, the wettability improved to be better than that of the 0.3 wt.%Si steel. Based on the surface oxide analysis results using SEM, FT-IR, and TEM analyses, the effect of the surface oxide type on the wettability is discussed. Although the morphology of the nanometer-sized surface oxides did not change, the surface oxides changed from MnO to Mn₂SiO ₄ to MnSiO₃ and then to SiO₂ as the Si content increased. After comparison of the present results with the wettability of pure oxides, it was concluded that the coating property of the dual phase high strength steel was more closely related to the type of surface oxide.