How is zinc securely plated onto steel?

The formation of a zinc layer on steel pipes involves quite 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 process" of hot-dip galvanizing as an example, steel pipes coated with zinc chloride flux are preheated to a temperature of 200-250°C in a drying oven before being dipped into molten zinc at 480-500°C. Firstly, the steel pipe absorbs a large amount of heat instantaneously, causing the zinc liquid on its surface to suddenly cool and solidify, forming a solid outer shell. Due to the continuous and abundant supply of heat, this shell melts quickly. When the surface temperature of the steel pipe balances with the temperature of the molten zinc, iron and zinc begin to interact. Therefore, the actual process of galvanizing steel pipes with zinc involves the following 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. When cooled, the pure zinc layer crystallizes, with the inner side of the zinc layer bonding to the steel pipe substrate. Thus, the hot-dip galvanizing process is primarily a process of forming a zinc-plated layer through diffusion.