How is zinc securely plated onto steel?

The formation of a zinc layer on steel pipes involves complex physical and chemical interactions between the steel pipes and molten zinc. When zinc is in a liquid state, it can erode and dissolve most metals, regardless of their melting points. Taking the "dry" hot-dip galvanizing process as an example, steel pipes coated with zinc chloride solvent are preheated to a temperature of 200-250°C in a drying oven before being immersed in molten zinc at 480-500°C. Initially, the steel pipes absorb a large amount of heat instantaneously, causing the zinc liquid on the pipe surface to solidify rapidly, forming a solid outer shell. Due to the continuous and abundant heat supply, this shell melts quickly. When the surface temperature of the steel pipes reaches equilibrium with the temperature of the molten zinc, iron and zinc begin to interact. Therefore, the actual process of galvanizing steel pipes with zinc follows these steps: solid iron dissolution; the combination of iron and zinc to form an iron-zinc alloy compound, resulting in an iron-zinc alloy layer; on the outer side of the iron-zinc alloy layer, a pure zinc layer is attached. Upon cooling, the pure zinc layer crystallizes, with the inner side of the zinc layer adhering to the steel pipe substrate. Thus, the hot-dip galvanizing process primarily involves the formation of a zinc coating through diffusion.