Galvanized steel pipe is a welded steel pipe with a hot-dip or electro-galvanized surface.

Galvanization can increase the corrosion resistance of steel pipes and prolong the service life.

Galvanized steel pipe has a wide range of uses, in addition to being used as a pipeline for general low pressure fluids such as water, gas and oil, it is also used as an oil well pipe and oil pipeline in the petroleum industry, especially in the marine oil fields, as an oil heater, condensation cooler and coal distillation and oil washing exchanger for chemical coking equipment, and as a support frame pipe for trestle pipe piles and mining pits, etc.

Classification of galvanized steel pipe.

Galvanized steel pipe is divided into cold galvanized steel pipe and hot galvanized steel pipe, cold galvanized steel pipe has been banned.

In the sixties and seventies, developed countries began to develop new types of pipes and banned galvanized pipes one after another.

Hot-dip galvanized steel pipes are widely used in fire fighting, electricity and highways.

Hot-dip galvanized pipe is made by reacting molten metal with iron substrate to produce an alloy layer, thus combining both the substrate and the coating.

Hot-dip galvanizing is done by pickling the steel pipe first, in order to remove the iron oxide on the surface of the pipe, pickling it and then cleaning it by ammonium chloride or zinc chloride in aqueous solution or mixed ammonium chloride and zinc chloride in aqueous solution bath, and then feeding it into a hot dip galvanizing bath.

Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The hot-dip galvanized steel pipe substrate reacts with the molten plating solution in a complex physical and chemical reaction to form a corrosion-resistant, structurally compact zinc-iron alloy layer.

The alloy layer is integrated with the pure zinc layer and the steel pipe substrate, so its corrosion resistance is strong.

Cold galvanized pipe is galvanized, the amount of galvanization is very little, only 10-50g/m2, its own corrosion resistance is much worse than the hot dip galvanized pipe.

Most of the regular galvanized pipe manufacturers do not use electro galvanizing (cold galvanizing) in order to ensure quality.

Only those small enterprises with small scale and outdated equipment use galvanizing, and of course their prices are relatively cheaper.

Cold galvanized steel pipe galvanized layer is an electroplated layer, the zinc layer and the steel pipe substrate independent of each other.

The zinc layer is thin, and the zinc layer is simply attached to the steel pipe matrix and easily peels off.

Therefore, its corrosion resistance is poor. In new residential buildings, it is prohibited to use cold galvanized steel pipes as water supply pipes.

Weight factor
Nominal wall thickness (mm): 2.0, 2.5, 2.8, 3.2, 3.5, 3.8, 4.0, 4.5.
Coefficient parameter (c): 1.064, 1.051, 1.045, 1.040, 1.036, 1.034, 1.032, 1.028.

Note: Steel mechanical properties are important indicators to ensure the final use of steel properties (mechanical properties), which depends on the chemical composition of steel and heat treatment system. In the steel pipe standard, according to the different requirements for use, specify the tensile properties (tensile strength, yield strength or yield point, elongation) and hardness, toughness indicators, and user requirements of high and low temperature properties, etc.

Grades of steel: Q215A; Q215B; Q235A; Q235B.
Test pressure value/Mpa: D10.2-168.3mm for 3Mpa; D177.8-323.9mm for 5Mpa

Galvanized steel pipe current national standards
Galvanized pipe national standards and size standards
GB/T3091-2015 Welded steel pipe for low pressure fluid transportation
GB/T13793-2016 Longitudinal electric welded steel pipe
GB/T21835-2008 Welded steel pipe size and weight per unit length


galvanized steel pipe factory

3.5 inch galvanized pipe