How is the zinc in hot-dip galvanizing firmly plated on steel?

How is the zinc in hot-dip galvanizing firmly plated on steel?

 

A layer of zinc is formed on the steel pipe after a very complex physical and chemical interaction between the steel and the molten zinc. When zinc is in a liquid state, it can corrode and dissolve general metals regardless of their melting point. Taking "dry" hot-dip galvanizing as an example, the steel pipe coated with zinc chloride solvent is preheated to a temperature of 200-250°C in a drying furnace and then enters the zinc liquid at a temperature of 480-500°C. First of all, the steel pipe absorbs a large amount of heat in an instant, causing the zinc liquid on the surface of the steel pipe to suddenly cool down, causing it to solidify on the surface of the steel pipe in an instant, forming a solid shell. Due to the continuous and large supply of heat, this layer The shell melts due to the rapid heat. When the surface temperature of the steel pipe and the temperature of the zinc liquid reach equilibrium, the solution and zinc begin to interact. Therefore, the actual process of galvanizing the steel surface is carried out according to the following steps: solid iron ferrolysis; iron and zinc combine to form iron-zinc The alloy compound produces an iron-zinc alloy layer; the outside of the iron-zinc alloy layer is connected to a pure zinc layer. When cooled, the pure zinc layer crystallizes, and the inside of the zinc layer is connected to the steel pipe matrix. Therefore, the hot-dip galvanizing process is mainly a process of forming a galvanized layer due to diffusion.