PIPE GALVANIZING
Pipe Galvanizing
Pipe galvanizing is the process of coating iron or steel with a layer of zinc. This helps to prevent corrosion and rust and is often used on pipes that will be exposed to the elements. The zinc provides a barrier against moisture and oxygen, which can cause iron and steel to corrode. In addition, zinc protects the metal from being damaged by ultraviolet light. The process of pipe galvanizing can be done in two ways: hot-dip galvanizing or pre-galvanizing. Hot-dip galvanizing involves dipping the pipes into a vat of molten zinc, while pre-galvanizing involves rolling galvanized coils into pipes. Both methods are effective at protecting the metal from corrosion, but hot-dip galvanizing is generally considered to be more durable. Pipe galvanizing is an important process that helps to prevent corrosion and rusting, and extends the life of metal pipes.
Why choose tuspipe?
Since 1998, Tianjin United Steel Pipe Co., Ltd (TUSPIPE) has been committed to supplying high-quality line pipes.
With over 500,000 tons annual production capacity, the company serves various fields and industries, such as oil & gas exploitation and transmission, ship & auto-building, water & electricity, environmental protection, mechanical engineering, infrastructure construction and etc.
TUSPIPE places a premium on product quality and rigorous product quality control. In order to maintain good product quality, the company has established a Test & Inspection Center since 2004. With a series of state-of-the-art tests and inspection equipment, the test & inspection center is able to perform the tensile tests, hydro tests, impact tests, DWTT, etc.
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.
Zinc has been used to protect iron and steel from corrosion for over a hundred years. The hot dip galvanizing process involves dipping the steel into a vat of molten zinc. The zinc bonds to the iron, forming a layer that prevents rust and corrosion. Hot dip galvanized pipe is used in a wide variety of applications, from residential to industrial. It is available in a variety of shapes and sizes, making it versatile for both new construction and repairs. When properly maintained, hot dip galvanized pipe can last for decades, making it an economical choice for both homeowners and businesses.
The pre-galvanized pipe is a steel pipe that has been coil coated with a zinc-based metallic coating prior to fabrication. The steel pipe is roll-formed, welded where necessary, and then passed through a high-speed set of rollers that form the desired shape. The zinc coating provides excellent corrosion resistance to the base metal, and this type of pipe is often used in construction and other applications where a long-lasting finish is required. While, due to the manufacturing method, the welding seam inside the pipe cannot be coated with zinc spray, so rust may still exist.
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 | Sth | 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 | – | – | – |
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.
