Hot-dip galvanizing was developed from the older hot-dip method. It has a history of 140 years since France applied hot-dip galvanizing to industry in 1836. However, the hot-dip galvanizing industry has developed on a large scale in the past thirty years with the rapid development of cold-rolled strip steel.
The production process of hot-dip galvanized sheets mainly includes: original sheet preparation→pre-plating treatment-→hot dip plating-→post-plating treatment-→finished product inspection, etc.
According to custom, the hot-dip galvanizing process is divided into two categories: off-line annealing and in-line annealing based on different pre-plating treatment methods, namely:
Wet method (single steel plate hot-dip galvanizing method)
Off-line annealing single steel plate hot dip galvanizing method
Hot-dip galvanizing Wheeling method (continuous hot-dip galvanizing method for strip steel)
In-line annealing Sendzimir method (protective gas method) modified Sendzimir method
U.S. Steel Federation Law (same as Japan's Kawasaki Law)
Selas method
Sharon Law
Off-line annealing: Before the hot-rolled or cold-rolled steel plate enters the hot-dip galvanizing line, it is first recrystallized and annealed in a bottom-type annealing furnace or a bell-type annealing furnace. In this way, there is no annealing process in the galvanizing line. Before hot-dip galvanizing, the steel plate must maintain a clean, pure iron active surface free of oxides and other dirt. This method is to first remove the annealed surface iron scale by pickling, and then apply a layer of zinc chloride or a solvent composed of a mixture of ammonium chloride and zinc chloride for protection, thereby preventing the steel plate from being oxidized again.
