Hot Dip Galvanized Pipe

Hot Dip Galvanized Pipe

The Hot Dip Galvanized steel pipe is a carbon steel pipe that has been zinc-coated for protection. Because the pipes are galvanized, they are resistant to rust and corrosion. Steel rusts overtime when it strikes the surface or moisture in the air. Galvanized steel round tube corrodes far slower when coated with zinc, extending the life of your tubing.

The process of coating iron, steel, or ferrous materials with a layer of zinc is known as hot-dip galvanizing (HDG). This is accomplished by passing the metal through molten zinc at 860°F (460°C) to generate zinc carbonate (ZNC03). Zinc carbonate is a robust substance that preserves steel and prevents corrosion in a variety of situations. Hot-dip galvanizing may be done cheaply and in huge quantities.

 PRODUCT FEATURES

The Application of Hot Dip Galvanized Pipe

Hot-dip galvanized steel pipe is mostly utilized in the transmission of coal, gas, and steam. It was utilized as a water pipe, but after a few years, there were many rusts in the pipe, and the water turned yellow from carrying iron oxide. The water not only contaminated dishes or other sanitary equipment but also carried bacteria generated on the interior surface of the non-smooth internal surface. As a result of corrosion, the water includes an excessive amount of heavy metal elements, which is damaging to people’s health. As a result, since the 1960s, developed countries have steadily prohibited its use as a water pipe. While hot dip galvanized pipes are increasingly being used in building projects due to their excellent corrosion resistance and lower cost than other coatings.

Dimensions and Sizes of Hot Dip Galvanized Pipe

DN

O. D.

W. T.

Inch

mm

SCH5S

SCH10S

SCH10

SCH20

SCH30

SCH40

SCH60

SCH80

SCH100

SCH120

SCH140

SCH160

STD

XS

XXS

50

2″

60.3

1.65

2.77

3.91

5.54

8.74

3.91

5.54

11.07

65

2 1/2″

73

2.11

3.05

5.16

7.01

9.53

5.16

7.01

14.02

80

3″

88.9

2.11

3.05

5.49

7.62

11.13

5.49

7.52

15.24

90

3 1/2″

101.6

2.11

3.05

5.74

8.08

5.74

8.08

100

4″

114.3

2.11

3.05

6.02

8.58

11.13

13.49

6.02

8.56

17.12

125

5″

141.3

2.77

3.4

6.55

9.53

12.7

15.88

6.55

9.53

18.05

150

6″

168.3

2.77

3.4

7.11

10.97

14.27

18.26

7.11

10.97

21.95

200

8″

219.1

2.77

3.76

6.35

7.04

8.18

10.31

12.7

15.09

18.26

20.62

23.01

8.18

12.7

22.23

250

10″

273.1

3.4

4.19

6.35

7.8

9.27

12.7

15.09

18.26

21.44

25.4

28.58

9.27

12.7

25.4

300

12″

323.9

3.96

4.57

6.35

8.38

10.31

14.27

17.48

21.44

25.4

28.58

33.32

9.53

12.7

25.4

350

14″

355.5

3.96

4.78

6.35

7.92

9.53

11.13

15.09

19.05

23.83

27.79

31.75

35.71

9.53

12.7

400

16″

406.4

4.19

4.78

6.35

7.92

9.53

12.7

16.66

21.44

26.19

30.96

36.53

40.49

9.53

12.7

450

18″

457.2

4.19

4.78

6.35

7.92

11.13

14.27

19.05

23.83

39.36

34.93

39.67

45.24

500

20″

508

4.78

5.54

6.35

9.53

12.7

15.09

20.62

26.19

32.54

38.1

44.45

50.01

550

22″

558.8

4.78

5.54

6.35

9.53

12.7

22.23

28.58

34.93

41.28

47.63

53.98

600

24″

609.6

5.54

6.35

6.35

9.53

14.27

17.48

24.61

30.96

38.89

46.02

52.37

59.54

The Process of Producing Hot Dip Galvanized Pipes

The procedure of manufacturing Hot Dip Galvanized Pipe is the same as that of manufacturing other steel materials. The immersion of iron or steel products in molten zinc to create a protective coating is known as hot-dip galvanizing. A metallurgical reaction happens between the iron in the steel and the molten zinc while the steel is immersed in the zinc. Because this is a diffusion-reaction, the coating forms perpendicular to all surfaces, resulting in a homogeneous thickness throughout the item.

Surface preparation, galvanizing, and inspection are the three essential processes in the hot dip galvanizing process.

shows the processes of hot dip galvanizing

- Surface Preparation

Surface preparation is an important step in applying any coating. When a coating breaks before the end of its projected service life, it is usually due to improper or insufficient surface preparation.

Because zinc will not react with dirty steel, the surface preparation phase in the galvanizing process has its own built-in quality control. Any flaws or deficiencies in surface preparation will be immediately visible when the steel is removed from the zinc bath because the unclean regions will remain uncoated, allowing for prompt corrective action.

- Three Steps during Surface Preparation

  1. Degreasing – Organic pollutants such as dirt, paint marks, grease, and oil are removed from the metal surface using a hot alkali solution, mild acidic bath, or biological cleaning bath. Epoxies, vinyl, asphalt, or welding slag that cannot be removed by degreasing must be removed by grit-blasting, sand-blasting, or other mechanical means before galvanizing.
  2. Pickling – Mill scale and iron oxides (rust) are removed from the steel surface using a dilute solution of hot sulfuric acid or ambient hydrochloric acid. In addition to or instead of pickling, this stage can be completed by abrasive cleaning or air blasting sand, metallic shot, or grit onto the steel.
  3. Fluxing – A zinc ammonium chloride solution is used for two purposes in the final surface preparation stage. It eliminates any remaining oxides and deposits a protective coating on the steel to prevent further oxide formation on the surface prior to immersion in the molten zinc.

- Galvanizing

When steel is entirely immersed in a bath (kettle) of molten zinc, the process is called “galvanizing.” The bath chemistry must be at least 98 percent pure zinc and kept at a temperature of around 840 F, according to the specifications (449 C). The crane hoist lowers the steel at an angle. This allows air to escape from tubular shapes or pockets that may be present in the design of a fabricated object, as well as molten zinc to displace the air.

The zinc reacts with the iron in the steel in the kettle to generate a sequence of zinc-iron intermetallic alloy layers. The coating growth is complete after the fabricated item reaches bath temperature, and the products are slowly removed from the galvanizing bath. Excess zinc is removed through draining, vibrating, and/or centrifugation. As long as the piece remains near bath temperature after being removed from the bath, the metallurgical reaction will continue. Articles are cooled either by immersing them in a passivation solution or by leaving them out in the open air.

- Inspection

The final stage of the procedure, inspection, is straightforward and rapid. Coating thickness and coating look are the two aspects of the hot-dip galvanized coating that is thoroughly scrutinized. Additional tests for adherence are given, however, they are normally only administered as a “referee” test or when an issue is detected.

A visual assessment of the material can provide a highly precise determination of the quality of the galvanized coating since, as previously indicated, zinc will not react with filthy steel. A range of basic physical and laboratory tests may also be done to check that the coating meets specification requirements for thickness, homogeneity, adhesion, and appearance. Products are galvanized in accordance with ASTM standards that have been long-established, accepted, and approved.

Hot Dip Galvanized Pipe with Threaded End

Threaded connections, which are commonly utilized on 3-inch hot-dip galvanized pipe or lesser sizes, are referred to as screwed pipe. Screwed pipe and screwed fittings can be quickly built without welding or other permanent means of attachment by using tapered grooves carved into the ends of a run of pipe. National Pipe Thread is the most used pipe thread (NPT).

The History of Hot Dip Galvanizing

Since 1742, the hot-dip galvanizing method has been utilized to provide long-lasting, maintenance-free corrosion protection at a reasonable cost. Although hot-dip galvanizing has been used to protect steel for decades, the galvanizing process is still evolving with new technology and innovative chemistries. Surface preparation, galvanizing, and post-treatment are the three primary processes in the hot-dip galvanizing process, and each will be addressed in detail. The technique is essentially simple, which gives it a significant advantage over other corrosion prevention approaches.

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