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The process of forming a hot-dip galvanized bolt layer is the process of forming an iron zinc alloy between the bolt and the outer layer of pure zinc. The surface of the workpiece forms an iron zinc alloy layer during hot-dip coating, which allows the iron and pure zinc layers to bond well. It can be simply described as: when the bolt is immersed in a molten zinc solution, a solid solution of zinc and alpha iron is first formed at the interface. The solid state of the iron matrix dissolves with zinc atoms to form a crystal, and the two metal atoms are fused together, with relatively little attraction between the atoms. Therefore, when zinc saturates in the solid solution, the two elements of zinc and iron diffuse into each other, and the zinc atoms diffused into the iron matrix migrate in the matrix lattice, gradually forming an alloy with iron. Iron diffuses into the zinc solution and forms the intermetallic compound FeZn13 with zinc, which sinks into the bottom of the hot-dip galvanized bolt, i.e. zinc slag. When hot-dip galvanized bolts are removed from the galvanizing solution, a pure zinc layer is formed on the surface, which is a hexagonal crystal with an iron content not exceeding 0.003%.