What Are GI Pipes
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GI pipes are made from mild steel (low-carbon steel) that has been coated with a layer of zinc (galvanized). This zinc layer provides corrosion protection.+2
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The process generally involves forming the pipe (ERW—Electric Resistance Welding) and then galvanizing, or galvanizing after welding, depending on product specifications.
Manufacturing & Standards
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Manufactured by Jindal Pipes Ltd. (JPL) under the Jindal Star brand.
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Sizes offered: From about ½″ (approx 15 mm NB) up to 14″ NB (and ERW black & galvanized pipes in some ranges up to 24″) depending on the plant and standard.+2
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Wall thicknesses vary with the class of pipe (Light, Medium, Heavy) as per Indian Standard IS:1239 (Part-1) for GI / ERW pipes.+3
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Other standards applicable: IS:1239, IS:3589, IS:1161; and international standards like BS, ASTM, API etc., depending on use and customer requirements.
Classes & Thickness (by IS:1239)
GI Pipes are classed as Light (Class A), Medium (Class B), and Heavy (Class C). These classes refer to wall thickness (for a given nominal bore). Some indicative size / thickness examples:
| Nominal Bore / Size | Outer Diameter (≈) | Light Class Thickness | Medium Class Thickness | Heavy Class Thickness |
|---|---|---|---|---|
| ½″ (15 mm) | ~21.3 mm | ~2.00 mm | ~2.60 mm | ~3.20 mm Textron Steel Alloys |
| ¾″ (20 mm) | ~26.7 mm | ~2.30 mm | ~2.60 mm | ~3.20 mm Textron Steel Alloys |
| 1″ (25 mm) | ~33.4 mm | ~2.60 mm | ~3.20 mm | ~4.00 mm Textron Steel Alloys |
| 2″ (50 mm) | ~60.3 mm | ~2.90 mm | ~3.60 mm | ~4.50 mm Textron Steel Alloys |
These are typical values; exact thickness depends on class & nominal bore.+2
Dimensions & Length
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Standard length for most GI pipe offerings from Jindal Star is 6 meters.+2
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Types of ends:
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Plain ends
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Screwed (threaded) ends — often used when connection to fittings is needed.
+2
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Galvanization & Coating
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The steel is coated with a zinc layer as per standard practices. The coating provides corrosion resistance; helps durability especially against rust, weather, moisture etc.
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For Jindal Star GI pipes, the zinc coating is done as per IS:4736 (which prescribes required mass of zinc coating on certain steel products) in some cases.
Mechanical Properties
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Tensile strength, yield strength etc. will vary depending on the thickness, material grade and process.
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Some product listings state tensile strength of around 370 MPa and yield strength about 210 MPa for certain GI pipes.
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The coating improves service life, but mechanical load capacity is mostly governed by the steel cross-section and wall thickness, not the zinc.
Applications & Suitability
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Widely used in water distribution, plumbing, sewage, fire-fighting systems etc. because of corrosion protection.
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Also used for structural purposes, engineering works, fabrication, electric poles, automotive, etc.
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Especially useful in environments where moisture or corrosive elements are present (coastal, humid etc.). The zinc helps resist rusting.
Advantages & Limitations
Advantages:
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Corrosion resistance due to zinc coating.
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Longer service life vs plain MS pipes in wet or exposed conditions.
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Easier to maintain.
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Strong welds / joints (since ERW process).
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Flexible in size, classes, end types.
Limitations:
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Zinc layer can wear off or get damaged; once damaged, steel beneath can corrode.
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Thicker GI pipes cost more due to more material and zinc.
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Heavier than thin-walled pipes for same nominal bore (esp. heavy class).
