line annealing is steel, hot rolled or cold milk into a line of people hot Man friends, since the first type annealing furnace or in the bottom of a bundle of bell type annealing furnace of recrystallization annealing, in this way, galvanizing line is no annealing process. Steel!Before hot galvanizing, the plate must maintain a clean, pure iron active surface free of oxides and other dirt.This approach is to first by pickling method by annealing the surface oxidation of iron removal, then coated with a layer by chloride, zinc or composed of ammonium chloride and zinc chloride mixed solvent, thus prevent the oxidation of the steel plate to be.(1) mixed hot-dip galvanizing: the surface of the steel plate is hot-dipped by zinc solution covered with molten solvent without drying (i.e. the surface is still wet). The disadvantages of this method are:A. Galvanized only in lead-free condition. The alloy coating is thick and has bad adhesion.B. grown zinc slag generated at the interface between zinc and lead liquid not deposit of pan (because of the zinc slag ratio, major in liquid zinc and lead is less than the liquid), such steel plate because of the polluted surface through the zinc layer. Therefore, this method has been largely eliminated.(2) the single plate: this method is generally adopted hot pack rolling plate as raw material, the first sent after annealing of steel pickling workshop, with sulfuric acid or hydrochloric acid removal method of oxygen on the surface of the steel plate galvanized iron sheet. After pickling, the steel plate immediately goes into the water tank to soak and wait for galvanization, which can prevent the steel plate from reoxidation. After acid washing, water washing, drying, drying, into the zinc pot (temperature has been maintained in 445-465 ℃) hot dip galvanized, then oil and chromium. The product quality of hot galvanized sheet produced by this method is significantly improved and high, which is of certain value only for small-scale production.(3) wheeling hot: the continuous galvanizing line including alkali degreasing, hydrochloric acid pickling solvent, water washing, coating, drying and so on a series of pretreatment process, and the original plate into galvanized in the galvanizing line is needed before the bell type furnace, annealing. The production process of this method is complex and the production cost is high. What's more, the products produced by this method are often contaminated with solvent defects, which affect the corrosion resistance of the coating. Moreover, AL in the zinc pot often interacts with the solvent on the surface of the steel plate to produce aluminum chloride, which is consumed and the adhesion of the coating is deteriorated. Therefore, although this method has been developed for nearly 30 years, it has been developed in the world.