Galvanized coil is a hot-rolled or cold-rolled steel plate as the base material, through the hot-dip plating or electric galvanizing process, plated on the surface of the steel plate with a layer of zinc, forming a good corrosion resistance of galvanized layer. Hot dip plating is to dip the steel plate into the molten zinc solution, and electric galvanizing is to deposit zinc layer on the surface of the steel plate using the principle of electrolysis.