Short description

Galvanized steel pipes are divided into cold galvanized steel pipes and hot-dip galvanized steel pipes. The use of cold galvanized steel pipes has been banned, while the latter is still temporarily recommended for use by the state. In the 1960s and 1970s, developed countries internationally began to develop new types of pipes and gradually banned the use of galvanized pipes. The Ministry of Construction of China and three other ministries also issued a document clearly stating that galvanized pipes should not be used as water supply pipes starting from 2000. Cold water pipes in new residential areas rarely use galvanized pipes anymore, although some residential areas still use galvanized pipes for hot water pipes. Hot-dip galvanized steel pipes are widely used in fire protection, electricity, and on highways.

Galvanized Steel Pipe Product Applications

  Hot-dip galvanized steel pipes are widely used in construction, machinery, coal mining, chemical, power, railway vehicles, automotive industry, highways, bridges, containers, sports facilities, agricultural machinery, petroleum machinery, prospecting machinery, greenhouse construction, and other manufacturing industries.
  Galvanized steel pipes have a surface with a hot-dip galvanized or electro-galvanized layer on welded steel pipes. Galvanization can increase the corrosion resistance of steel pipes and extend their service life. The uses of galvanized pipes are extensive, including not only as pipes for water, gas, oil, and other general low-pressure fluid pipelines, but also as oil well pipes and oil pipelines in the petroleum industry, especially for offshore oil fields, pipes for oil heaters, condensers, and coolers in coking equipment for the chemical industry, pipes for coal distillation and oil exchange, as well as pipes for pier piles and support frames in mine tunnels.

Hot-dip galvanized pipe

Hot-dip galvanized steel pipes are produced by reacting molten metal with an iron substrate to form an alloy layer, thereby combining the substrate and the coating. Hot-dip galvanizing involves first pickling the steel pipes to remove the iron oxide from their surface. After pickling, the pipes are cleaned in a bath of ammonium chloride or zinc chloride solution, or a mixed solution of ammonium chloride and zinc chloride, before being sent into the hot-dip galvanizing tank. Hot-dip galvanizing has advantages such as uniform coating, strong adhesion, and long service life. During the hot-dip galvanizing process, the steel pipe substrate undergoes complex physical and chemical reactions with the molten zinc bath, forming a tightly structured zinc-iron alloy layer that is resistant to corrosion. This alloy layer merges with the pure zinc layer and the steel pipe substrate, giving it a strong resistance to corrosion.

Cold galvanized pipe

Cold galvanized pipes are essentially electro-galvanized, with a very small amount of zinc coating, ranging from 10 to 50 grams per square meter. Their corrosion resistance is significantly lower than that of hot-dip galvanized pipes. Manufacturers of galvanized pipes, to ensure quality, mostly do not use electro-galvanizing (cold plating). Only small enterprises with outdated equipment use electro-galvanizing, and of course, their prices are relatively cheaper. The Ministry of Construction has officially issued a document to phase out the technologically backward cold galvanized pipes, prohibiting their use for water and gas pipes. The galvanized layer of cold galvanized steel pipes is an electroplated layer, with the zinc layer and the steel pipe substrate being independently stratified. The zinc layer is relatively 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, the use of cold galvanized steel pipes as water supply pipes is prohibited.

Galvanized Steel Pipe Weight Factor

Nominal Wall Thickness (mm): 2.0, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5.
Factor Parameter (c): 1.064, 1.051, 1.045, 1.040, 1.036, 1.034, 1.032, 1.028.
Note: The mechanical properties of steel are important indicators to ensure the final performance (mechanical properties) of steel, which depend on the chemical composition and heat treatment system of the steel. In the steel pipe standards, according to different usage requirements, tensile properties (tensile strength, yield strength or yield point, elongation), as well as hardness, toughness indicators, and high and low temperature performance required by users are specified.
Steel Grade: Q215A; Q215B; Q235A; Q235B.
Test Pressure Value/Mpa: 3Mpa for D10.2-168.3mm; 5Mpa for D177.8-323.9mm.
Current National Standard for Galvanized Steel Pipes
National Standards and Size Standards for Galvanized Pipes
GB/T3091-2015 Welded Steel Pipes for Low Pressure Fluid Delivery
GB/T13793-2016 Straight Seam Electric Welded Steel Pipes
GB/T21835-2008 Welded Steel Pipe Dimensions and Unit Length Weight

Uses of Galvanized Steel Pipes

Instructions for the Use of Galvanized Steel Pipes
The commonly referred galvanized pipes, the type of iron pipe used for gas and heating, are also galvanized pipes. As water pipes, after several years of use, galvanized pipes can accumulate a large amount of rust and scale inside. The yellow water that flows out not only pollutes the sanitary ware but also carries bacteria that grow on the rough inner walls. The rust corrosion causes the content of heavy metals in the water to be excessively high, severely endangering human health.