Hot dip galvanizing is to make molten metal and iron matrix reaction and produce alloy layer, so as to combine the matrix and coating.  Hot dip galvanizing is the first steel parts pickling, in order to remove iron oxide on the surface of steel parts, 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