What are the types of galvanized steel pipes?

1. Hot dip galvanized pipes produce an alloy layer by reacting molten metal with an iron substrate, thereby bonding the substrate and coating together. Hot dip galvanizing is the process of first pickling steel pipes. In order to remove iron oxide from the surface of the steel pipes, after pickling, they are cleaned in an ammonium chloride or zinc chloride aqueous solution or a mixed ammonium chloride and zinc chloride aqueous solution tank, and then sent to a hot-dip galvanizing tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The hot-dip galvanized steel pipe undergoes complex physical and chemical reactions with the molten plating solution, forming a corrosion-resistant and tightly structured zinc iron alloy layer. The alloy layer is integrated with the pure zinc layer and the steel pipe substrate. Therefore, it has strong corrosion resistance.

2. Cold galvanizing is also known as electroplating galvanizing, with a very small amount of galvanizing, only 10-50g/m2. Its corrosion resistance is much different from that of hot-dip galvanized pipes. The zinc layer of cold galvanized steel pipes is an electroplating layer, which is independently layered with the steel pipe substrate. The zinc layer is relatively thin and easily adheres to the steel pipe substrate, making it prone to detachment. Therefore, its corrosion resistance is poor. Cold galvanized steel pipes are prohibited from being used as water supply pipes in newly constructed residential buildings.