Knowledge about steel pipes: Classification of galvanized steel pipes
2013-07-18
Galvanized steel pipes are divided into cold galvanized pipes and hot galvanized pipes. The former has been banned, while the latter is still temporarily encouraged by the state for use.
Hot galvanized pipe:
Hot galvanized pipe is produced by having molten metal react with the iron substrate to form an alloy layer, thus combining both the substrate and the coating. Hot galvanizing involves first pickling the steel pipe to remove surface iron oxide, followed by cleaning in a solution of ammonium chloride or zinc chloride, or a mixed solution of ammonium chloride and zinc chloride, before being sent to the hot dip galvanizing tank. Hot galvanizing has advantages such as uniform coating, strong adhesion, and long service life.
Hot galvanized steel pipe: The steel pipe substrate undergoes complex physical and chemical reactions with the molten plating solution, forming a corrosion-resistant tightly structured zinc-iron alloy layer. The alloy layer integrates with the pure zinc layer and the steel pipe substrate, resulting in strong corrosion resistance.
Cold galvanized pipe:
Cold galvanizing refers to electro-galvanizing, which has a very low zinc coating amount of only 10-50g/m2. Its corrosion resistance is significantly inferior to that of hot galvanized pipes. Reputable galvanized pipe manufacturers mostly do not use electro-galvanizing (cold galvanizing) to ensure quality. Only small enterprises with outdated equipment use electro-galvanizing; naturally, their prices are relatively cheaper. Currently, the Ministry of Construction has officially issued a document to eliminate outdated cold galvanized pipes and prohibits their use for water and gas pipelines in the future.
Cold galvanized steel pipe: The zinc layer is an electroplated layer that is independently layered from the steel pipe substrate. The zinc layer is thin and simply adheres to the steel pipe substrate, making it prone to peeling off. Therefore, its corrosion resistance is poor. In new residential buildings, using cold galvanized steel pipes as water supply pipes is prohibited.
Shenyang Tengfei Iron Corporation
Shenyang Tengfei Steel Pipe Co., Ltd.
Address: No.6 A 3, No.13 Road, Economic and Technological Development Zone, Shenyang City, Liaoning Province
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