(1) the definition of 40g, 60g, 80g, 100g, 120g, 180g, 200g, 250g, 275g, 280g, etc.:: DX51D + Z galvanized zinc coating to prevent corrosion of the steel surface subjected to prolong its life, the steel surface is coated with a layer of metallic zinc, zinc-coated steel sheet which is known as galvanized steel. (2) Classification and Uses: According to the production and processing methods can be divided into the following categories: ① hot-dip galvanized steel. The steel sheet was immersed in molten zinc bath, so that the surface adhesion layer of zinc sheet steel. At present, continuous galvanizing production process, that is, to become immersed in a continuous roll of steel melting zinc plating bath is made of galvanized steel; ② alloyed galvanized steel. This steel is manufactured by hot dipping, but after the trough, immediately it is heated to about 500 ℃, it generates zinc and iron alloy coating. This galvanized coatings with good adhesion and weldability; ③ galvanized steel. Such manufacturing galvanized steel sheet having excellent workability by plating. But the coating is thin, the corrosion resistance is better hot-dip galvanized sheet method; ④-sided and double-sided difference galvanized steel plating. Single-sided galvanized steel, i.e., only one side of galvanized products. In terms of welding, painting, rust treatment, processing, has a better than two-sided galvanized sheet flexibility. To overcome the disadvantages of single uncoated zinc, another one on the other side is coated with a thin layer of zinc galvanized sheet, ie the difference between double-sided galvanized sheet; ⑤ alloy, composite galvanized steel. It is steel with zinc and other metals such as lead, zinc alloy and even made into composite plating. This plate has both excellent rust resistance, and good coating performance.