The process of forming a hot-dip galvanizing layer is a process of forming an iron-zinc alloy between the iron matrix and the outermost pure zinc layer. When the surface of the workpiece forms an iron-zinc alloy layer during the hot dip plating, only the iron and the pure zinc layer are formed. For a good combination, the process can be simply described as follows: When the iron workpiece is immersed in the molten zinc liquid, a solid solution of zinc and alpha iron (body center) is first formed at the interface. This is a crystal formed by the dissolution of zinc atoms in the solid state of the base metal iron. The fusion between the two metal atoms is relatively small. Therefore, when zinc is saturated in the solid solution, the two elements of zinc and iron diffuse into each other, and the zinc atoms diffused into (or infiltrated into) the iron matrix migrate in the matrix of the matrix, gradually forming an alloy with iron, and diffuse. The iron in the molten zinc liquid forms an intermetallic compound with zinc and sinks into the bottom of a hot-dip galvanizing pot, namely, dross. When the workpiece is removed from the zinc bath, the surface forms a pure zinc layer, which is a hexagonal crystal. Its iron content is not more than 0.003%.