Steel pipe substrate and the molten bath complex physical, chemical reactions, the formation of corrosion-resistant structure of zinc-iron alloy layer. Alloy layer and the layer of pure zinc, steel matrix blend. So the corrosion resistance ability. 
 The zinc layer is independent of stratification of the plating layer, the zinc layer and the steel pipe substrate. The zinc layer is very thin zinc layer is simply attached to the steel pipe substrate is easy to fall off. Therefore, its poor corrosion resistance. In new residential, prohibit the use of cold galvanized steel pipe