PIPE GALVANIZING

Pipe Galvanizing

Pipe galvanizing is a coating process that gives steel pipe a zinc coating to prevent corrosion and rust. Pipe galvanizing was widely used in residences constructed. When it was introduced, galvanized pipe was an alternative to lead pipe for water supply lines.

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Why Using Pipe Galvanizing?

Without pipe galvanizing, corrosion is a persistent danger to metal; therefore, it must be protected. It is possible to create oxidation in metal when corrosive elements such as salt, dirt, moisture, or chemicals come into contact with the iron in the metal. Rust is formed as a consequence of the reaction. Because of the corrosion of metal, pipes are at risk of collapsing or exploding.

Adding a coating of zinc to metal during the pipe galvanizing process serves to protect it against corrosion. This zinc reinforcement provides two types of protection for metals:

  • It acts as a protective barrier between the sensitive iron and the corrosive elements.
  • Galvanic corrosion is prevented by using this product. When compared to the majority of metals, zinc exhibits significantly anodic characteristics. When it comes into touch with a more noble metal, it acts as an anode, releasing electrons very immediately. When a noble metal would otherwise be taking electrons from carbon steel or another basic metal, this sacrifice comes in useful.

Types of PIPE GALVANIZING

There are two common types of pipe galvanizing you can easily found in the market.

In terms of dependability, hot-dip pipe galvanizing is one of the most effective pipe galvanizing methods available. According to the American Galvanizers Association, hot-dip pipe galvanizing structural steel may extend the life of the steel by more than 70 years. During the pipe galvanizing process, you need to dip your metal into a solution of liquid zinc. Because it allows you to immerse the whole thing at once, it is an excellent choice for pipe supports of various shapes and sizes.

Product shapes that are constant, such as metal sheets or plates, are typical candidates for pre-galvanized coatings. Pre-galvanizing metal is accomplished by passing it through a zinc wash. Pre-galvanizing, on the other hand, is often done before manufacturing, as the name indicates. This implies that any cuts made during the production process will be exposed to corrosive elements.

Dimensions and Sizes of 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 Pipe Galvanizing

The technique for producing Hot Dip Galvanized Pipe is the same as the procedure for making other steel products, including stainless steel. Hot-dip pipe galvanizing is the process of immersing iron or steel goods in molten zinc in order to coat them with a protective layer of zinc. The iron in the steel reacts with the molten zinc when the steel is submerged in it, resulting in metallurgical reactions between the iron and the zinc. This is because the coating develops perpendicular to all surfaces as a consequence of the diffusion process, which results in a uniform thickness across the object.

During the hot-dip pipe galvanizing process, surface preparation, galvanizing, and inspection are the three most important operations to perform.

shows the processes of hot dip galvanizing

- Surface Preparation

Surface preparation is a critical stage in the application of any coating or finish. When a coating fails before it has had a chance to reach the end of its expected service life, it is almost often due to incorrect or inadequate surface preparation.

Because zinc will not react with rusted or corroded steel, the surface preparation step of the galvanizing process has its own built-in quality control mechanism. The presence of any faults or shortcomings in surface preparation will be instantly apparent when the steel is taken from the zinc bath because the dirty portions will remain uncoated, allowing for fast correction of the problem.

- Galvanizing

According to the standards, the bath chemistry must include at least 98 percent pure zinc and is maintained at a temperature of around 840 degrees Fahrenheit (449 C). The steel is lowered at an angle by the crane hoist. In addition to allowing air to escape from tubular forms or pockets that may be included in the design of a produced item, it also enables molten zinc to displace the air that has been trapped within.

The zinc interacts with the iron in the steel in the kettle, resulting in the formation of a series of zinc-iron intermetallic alloy layers in the kettle. After the manufactured item reaches bath temperature, the coating development is complete, and the items are gently withdrawn from the galvanizing bath. Draining, vibrating, and/or centrifuging are used to remove excess zinc from the solution. The metallurgical reaction will continue as long as the item is kept at or near bath temperature after it has been taken from the bath. Cooling articles may be accomplished in two ways: by immersing them in a passivation solution or by putting them out in the open air to cool.

- Inspection

The last part of the operation, inspection, is basic and takes just a few minutes to complete. Both the coating thickness and the appearance of the hot-dip galvanized coating are closely evaluated when it comes to this kind of coating. Additional tests for adherence are performed; however, they are often only performed as a “referee” test or when a problem is identified with the patient.

Because, as previously stated, zinc will not react with unclean steel, a visual inspection of the material may offer a very accurate evaluation of the quality of the galvanized coating. A variety of fundamental physical and laboratory tests may also be performed to ensure that the coating fulfills all of the specifications for thickness, homogeneity, adhesion, and appearance, among other things. Products are galvanized by ASTM standards, which have been in use for many years and are widely acknowledged and approved by the public.

The Process of Producing Pre-Galvanized Pipe

The production of pre-galvanized pipe is quite similar to that of welded pipe. The only difference is in the raw material and zinc spray. A pre-galvanized pipe is made from pre-galvanized strips, which are galvanized prior to pipe manufacture. However, since the welding seam will be the only section that does not have a zinc coating, a zinc spray technique must be done following the welding process.

Difference between Hot Dip Galvanizing and Pre-Galvanizing

An automated approach may also be used to galvanize pre-galvanized pipe to EN 10240. Immersion durations are short, and steam may be forced into the bore of the tube after extraction to create a smooth surface finish. Although coating thicknesses of 45-55 m are possible, the bulk of products manufactured have a significantly thinner covering of 20-30 m.

Because pre-galvanized pipe components are often only submerged in the galvanizing solution for a brief amount of time, the coating is rather thin. Hot-dip galvanization results in a thicker zinc coating than pre-galvanization, which offers superior rust and corrosion protection, particularly for pipes that are regularly used outdoors and exposed to snow, ice, rain, and salt.

The zinc coating on the steel sheet must meet the requirements of ASTM A525 Grade G90 and G120. The total zinc weight of the exterior and interior surfaces shall be between 0.90 oz/sq ft (or 0.45 oz/sq ft each side) and 1.20 oz/sq ft (or 0.60 oz/sq ft each side). These coating weights do not apply to the inner welded region.

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)

Advantages of Pipe Galvanizing

So, how can galvanizing your piping system benefit you and your business? The following are some of the advantages of galvanizing pipe supports.

- Cost-Effectiveness

The question you may be asking is: “If pipe galvanizing provides anti-corrosive characteristics, why not just utilize stainless steel pipes?” The solution is a matter of money. However, although stainless steel has corrosion resistance built into its design, it is often more costly than conventional carbon steel. Consequently, galvanizing is a reasonably inexpensive method of adding an additional layer of protection to otherwise durable materials.

- Performance

Alternatives such as paint or other basic coverings, on the other hand, may seem to be a straightforward answer. However, they are not without their drawbacks. For starters, they often chip or scrape the surface, exposing the underlying metal to rust. Second, since they are readily worn away, they must be reapplied on a regular basis. Finally, when subjected to extreme temperature fluctuations or external erosion, they have a tendency to flake or peel off.

- Less Labor-Intensive

Galvanized metal is subjected to a rigorous production process, but after it has been applied to metal, the product is ready to be sent out the door. As a result, your team will not be burdened with the time-consuming and labor-intensive operations of applying paints or other coatings. You will also save time by not having to spend time prepping surfaces, monitoring supports for scratches, or repainting your walls.

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