Hot-dip galvanizing is a process technology that involves immersing steel, stainless steel, cast iron, and other metals into molten liquid metal or alloy to form a coating. It is one of the most cost-effective and widely used steel surface treatment methods in the world today. Hot-dip galvanized products not only significantly reduce corrosion of steel and extend its lifespan but also contribute to energy and material saving, playing an irreplaceable role. Galvanized steel is also one of the high value-added short-term products supported and prioritized for development by the country.
During the hot-dip galvanizing process, an iron-zinc alloy layer is formed between the iron base and the outermost pure zinc layer. A zinc-iron alloy layer is formed on the surface of the workpiece during hot-dip galvanizing, ensuring a good bond between iron and the pure zinc layer. In simple terms, when an iron workpiece is immersed in molten zinc, a zinc-alpha iron eutectic is first formed at the interface. This eutectic is a crystal formed by iron atoms in a solid state that dissolve zinc atoms, with weak gravitational forces between the two types of metal atoms. Once zinc saturates the eutectic, zinc and iron atoms diffuse into each other, with zinc atoms gradually migrating into the iron matrix to form an alloy. Iron in the zinc bath forms intermetallic compounds with zinc, settling to the bottom of the hot-dip galvanizing kettle as zinc dross. When the workpiece is removed from the zinc bath, a pure zinc layer forms on the surface, exhibiting a hexagonal crystal structure with an iron content of no more than 0.003%.