For galvanized steel coils, the steel sheet is immersed in a molten zinc bath to make a sheet of zinc coated on its surface. It is mainly produced by continuous galvanizing process, that is, the rolled steel plate is continuously immersed in a plating tank with zinc melted to make galvanized steel plate; alloyed galvanized steel plate. This kind of steel plate is also manufactured by hot dip method, but immediately after being out of the tank, it is heated to about 500 ℃ to form an alloy coating of zinc and iron. This galvanized coil has good paint adhesion and weldability.