The significance of hot dip galvanizing is that the corrosion resistance of steel strip is greatly improved after the surface of steel strip is covered by a layer of galvanized layer, which can save materials and resources and bring good economic and environmental benefits into play. The protective effect of galvanized layer on steel strip is mainly as follows.
(1) when the surface of galvanized plate is intact, only zinc corrosion, because the zinc corrosion products have a good protective effect on zinc, so the corrosion speed is very slow, the life is not galvanized steel l5 ~ 30 times.
(2) the most common situation is in the processing, installation and use of galvanized sheet, surface scratches, or other reasons make the local destruction of coating, the steel strip from the wound is exposed to the environment, if the coating is nonmetal material, the steel base will soon be exposed by the corrosion, but the special sacrifice protection performance of galvanized sheet, make the corrosion speed becomes very slow.
（3）In this case, the zinc in the coating and the iron in the strip form a galvanic cell in a humid environment. Since the standard electrode potential of zinc is only -1.05V, lower than the -0.036V of iron, zinc is oxidized as an anode and iron is protected as a cathode. Because the product after zinc corrosion is very dense, the reaction speed is very slow, that is to say, the overall corrosion resistance is greatly improved. This method of preservation is called sacrificial preservation.
