Influence of substrate oxidation on dynamic wetting in hot dip Al-Zn-Si coatings

In metallic hot dip coating processes, the formation of a thin continuous and uniform alloy layer is critical in providing the vital metallurgical bond at the substrate-coating melt interface. When the alloy layer isn't uniform, bare spots or uncoated areas are formed which greatly affect the corrosion resistance and surface appearance of the coated product. Direct and indirect dynamic measurements of mass transfer during metallic coating are difficult, if not impossible. However, the concept of interfacial resistance to mass transfer is analogous to that of interfacial resistance to heat transfer. Using this concept, measurements based on dynamic reactive wetting and thermal interfacial resistance were performed at millisecond resolution to study the effects of low carbon substrate oxidation on the formation of 55Al-Zn-1.6Si hot dip coatings. The effect of substrate oxidation on the dynamic wetting of 55Al-Zn-1.6Si hot dip coating melts on low carbon steel substrates was investigated using an experimental apparatus based on the sessile drop technique.