What are the classifications of galvanized pipes?

When the galvanized pipe was first born, it was still a very popular product. Generally, the galvanized pipe we often say is now mainly used to transport gas and heating. In the past, many galvanized pipes were used as water pipes. What are the classifications of galvanized pipes?
1. Hot-dip galvanized pipe: react the molten metal with the iron substrate, so that an alloy layer can be produced, and the substrate and the coating can be combined. Hot-dip galvanizing is to pickle the steel pipe first. In order to remove the iron oxide on the surface of the steel pipe, it needs to be washed in ammonium chloride, zinc chloride aqueous solution, ammonium chloride chloride or zinc chloride mixed aqueous solution tank after pickling, and then into the hot-dip coating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life.
2. Cold galvanized pipe: cold galvanized is electro-galvanized, the amount of galvanized is very small, only 10-50g/m2, and its corrosion resistance is much worse than that of hot-dip galvanized pipe. The galvanized pipe manufacturer of the track, in order to ensure the quality, the large purchase of JDG threading pipe does not use electro-galvanizing (cold plating). Only small companies with small equipment and outdated equipment use electro-galvanized steel, of course, their prices are relatively cheaper. At present, the Ministry of Construction has officially laid down the cold-galvanized pipe with backward technology, and it is not allowed to use cold-galvanized pipe as water and gas pipe in the future.
3. Hot-dip galvanized steel pipe: The steel pipe substrate and the molten plating solution undergo complex physical and chemical reactions to form a corrosion-resistant zinc-iron alloy layer with a tight structure. Then the alloy layer is integrated with the pure zinc layer and the steel pipe substrate. Therefore, it has strong corrosion resistance.
4. Cold galvanized steel pipe: the zinc layer is an electroplating layer, and the zinc layer is independently layered with the steel pipe substrate. The zinc layer is relatively thin, and the zinc layer is easily attached to the steel pipe substrate and is easy to fall off. Therefore, its corrosion resistance is poor. In newly built houses, it is forbidden to use cold-galvanized steel pipes as water supply pipes.