Galvanized steel sheet is mainly divided into hot-dip galvanized steel sheet, alloy galvanized steel sheet, electro galvanized steel sheet, single-sided galvanized steel sheet and double-sided differential galvanized steel sheet. Hot dip galvanized steel sheet is a thin steel sheet that is dipped into the molten zinc bath to make its surface adhere to a layer of zinc. The alloyed galvanized steel sheet is also manufactured by hot dip method, but it is heated to about 500 ℃ immediately after being out of the groove, so that it can form an alloy film of zinc and iron. The galvanized steel sheet is made by electroplating. Single side galvanizing refers to products that are galvanized on one side only. In order to overcome the disadvantage that one side is not coated with zinc, another kind of galvanized sheet is coated with a thin layer of zinc on the other side, that is, double-sided galvanized sheet.