Hot dip galvanizing is the reaction of molten metal with iron matrix to produce alloy layer, so that the matrix and the coating are combined. Hot dip galvanizing is the first steel parts for pickling, in order to remove iron oxide on the surface of steel parts, after pickling, through ammonium chloride or zinc chloride aqueous solution or ammonium chloride and zinc chloride mixed aqueous solution tank for cleaning, and then into the hot dip plating tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion and long service life.