PRE-Galvanized Pipe

Pre-Galvanized Pipe

Pre-Galvanized Pipe shall be made from pre-galvanized steel strip in accordance with ASTM A446. The coated steel must be cold shaped and welded into the tube using a high-frequency induction welding process capable of producing a weld bead that is stronger than the parent metal. The exterior coating that has been damaged during welding must be restored by metalizing (spraying molten zinc wire). The interior weld area that has been damaged during welding must be left unprotected.

 PRODUCT FEATURES

The Application of Pre-Galvanized Pipe

Pre-galvanized steel pipes are widely utilized in a variety of applications, including steel structures, building structures, guard rails, fences, metal furniture, solar structures, and so on.

Dimensions and Sizes of Pre-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 Pre-Galvanized Pipe

The manufacturing process of pre-galvanized pipe is very similar to that of normal welded pipe. The only differences are the raw material and zinc spray. The raw material of the pre-galvanized pipe is pre-galvanized strips, and the strips are galvanized already before pipe production. However, the welding seam will be the only part without zinc coating, so the zinc spray process shall be applied after the welding process.

What is Pre-Galvanizing?

When steel components are used in the manufacturing of a more sophisticated completed product, they may be galvanized before assembly. This is referred to as pre-galvanization, or “pre-gal.” It is also known as “in-line,” “continuous,” or “mill” galvanizing. Steel components, such as sheets or wire, are galvanized using an automated process before being reduced to size.

Depending on the type of component being galvanized, this automated procedure will vary. In general, the steel components are immersed for a short time in a “galvanizing bath” of molten zinc. Excess zinc is removed from the steel after it has been taken from the bath using a mechanical wiper, air knife, or steam. This results in somewhat thin zinc galvanized coating.

The Performance of Pre-Galvanized Pipe

The pre-galvanized pipe can also be galvanized to EN 10240 utilizing an automated technique. Immersion times are quite brief, and steam may be pushed through the bore of the tube after extraction to provide an acceptable surface finish. Although the coating thickness can reach 45-55 m, the majority of the product produced has a much thinner coating of 20-30 m.

Because pre-galvanized pipe materials are normally only immersed in the galvanizing bath for a short period of time, the coating is rather thin. Hot-dip galvanization produces a thicker zinc coating than pre-galvanization, which provides better rust and corrosion protection, especially for pipes that are frequently used outside and exposed to snow, ice, rain, and salt.

The zinc coating on the steel sheet must be in accordance with ASTM A525 Grade G90 and G120. The combined zinc weight of the external and interior surfaces must range from 0.90 oz/sq ft (or 0.45 oz/sq ft each side) to 1.20 oz/sq ft (or 0.60 oz/sq ft each side). These coating weights do not apply to the welded area on the inside.

The Difference Between Hot Dip Galvanizing and Pre-Galvanizing

Feature

Hot Dip Galvanization

Pre-Galvanizing

Coating Thickness

Thick coating with minimum average requirements of 45-85μm within BS EN ISO 1461

The coating thickness may vary, but it is typically circa 20μm for sheets and 20-30μm for tubes

Coating Continually

Continuous coating over the whole object

The uncoated area at cut edges

Coating Bond

Strong metallurgical bond with the base steel

Strong metallurgical bond with the base steel

Coating Formability

Forming after hot dipped galvanizing is not advised as it may damage the coating

A thin coating may be normally formed without any damage

Coating Appearance

Normally bright, but can be variable

Normally bright

Abrasion Resistance

A thicker layer of hard zinc-iron alloy gives a high resistance to abrasion

Thin alloy layer with reduced resistance to abrasion

Sacrificial Protection

Offer the highest level of sacrificial protection

Reduced sacrificial protection due to thin layer coating and at some uncoated areas (cut edges)

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