Galvanized square pipe is made from hot-rolled or cold-rolled steel strips, processed through welding or cold bending to form square-section pipes. A galvanized coating forms a corrosion-resistant layer, commonly available in cold-dip galvanizing and hot-dip galvanizing methods. The corrosion protection lifespan can reach 50 years. It possesses excellent mechanical properties and corrosion resistance, and is widely used in construction, machinery, transportation, and other fields.
Glory Steel supplies hot-dip Square GI pipes with zinc coatings ranging from Z30 to Z275. As a top-tier supplier in China, we can customize and produce square tubing in all sizes.
Specification
| Item | Galvanized Square Tubes |
| Country of Origin | Tianjin, China |
| Surface Treatment | Galvanized |
| Coating | Z30-Z275 |
| Cross-sectional Shape | Square, Rectangular |
| Material | Q195, Q215, Q235 (A/B), Q345 (B/C/D/E), S275/JR, S355JR, A53, st37, 10#-45#, etc. |
| Standards | GB, ASTM, JIS, BS, AISI, EN, DIN, API |
| Certifications | ISO9001, API, CE, JIS, GS, etc. |
| Length | 1-12m (6m/6.4m/12m) |
| Wall Thickness | 0.5-25mm |
| Production Process | ERW, Cold-rolled, Hot-rolled/Cold-rolled |
| Packaging | Standard Airworthiness |
Features
- Excellent Corrosion Resistance: The zinc layer formed on the surface through the galvanizing process provides rust and oxidation resistance, significantly extending service life. Service life can reach over 20 years in suburban, urban, and coastal areas.
- Good Mechanical Properties: The base material is carbon steel square tubing, which inherently possesses high strength and rigidity, impact resistance, and can withstand large loads. It can be used for structural support.
- Excellent Processing Performance: It can be welded, cut, and bent, making installation simple. It is suitable for everything from door and window frames to large steel structure projects, offering a variety of sizes and high construction efficiency.
- High Cost-Effectiveness: The galvanized layer has a smooth surface and uniform color, allowing for direct exposed use. It has low maintenance costs, a long service life, and overall cost-effectiveness.
Application areas
- Construction Engineering and Steel Structure Products: Columns, beams, and support pipes for steel structure buildings, stadiums, and bridges; pipe racks for plumbing systems, drainage pipes, and stair handrails; curtain wall frames; door and window fabrication; underground pipe support and wiring.
- Industrial Manufacturing and Supports: Manufacturing of agricultural and chemical machinery; materials for oil well drilling and pipelines in the oil and gas industry; photovoltaic supports; advertising racks, etc.
- Transportation and Municipal Engineering: Automobile frames and chassis; subway and highway guardrails; street light poles; pipes for charging stations.
- Furniture and Agriculture: After welding, it can be used as animal and field fences; table, chair, and shelf materials; water supply, drainage, and pipeline materials.
Production process
Hot-dip galvanized square tube
Hot-rolled/cold-rolled steel sheet/strip → Cold bending + high-frequency welding → Pickling and rust removal → Neutralization and cleaning → Drying → Hot-dip galvanizing (450-500℃ zinc bath) → External blowing for zinc removal/Internal blowing for slag removal → Water cooling and curing → Passivation treatment → Eddy current testing + hydrostatic testing → Finished product inspection → Packaging and warehousing.
Electro-galvanized (cold galvanizing) Square tube
Surface pretreatment → Electro-galvanizing (zinc salt solution electrolytic deposition) → Water washing → Drying → Finished product inspection → Packaging and warehousing.
Quality Inspection Process
- Raw Material: Verify steel grade, certificates, and surface quality.
- Production: Control forming dimensions, ensure sound welding, and maintain uniform zinc coating.
- Finished Product: Check dimensions, zinc layer thickness, pressure tightness, and surface finish.
Galvanized square pipe weight chart
| Outer side length (mm) | WT(mm) | Weight (kg/m) |
| 20×20 | 1.0 / 1.2 / 1.5 | 0.59 / 0.69 / 0.83 |
| 25×25 | 1.0 / 1.2 / 1.5 / 2.0 | 0.75 / 0.88 / 1.08 / 1.40 |
| 30×30 | 1.5 / 2.0 / 2.5 | 1.33 / 1.73 / 2.11 |
| 40×40 | 1.5 / 2.0 / 2.5 / 3.0 | 1.81 / 2.37 / 2.91 / 3.43 |
| 50×50 | 2.0 / 2.5 / 3.0 / 4.0 | 3.02 / 3.72 / 4.40 / 5.69 |
| 60×60 | 2.0 / 2.5 / 3.0 / 4.0 | 3.67 / 4.53 / 5.37 / 6.98 |
| 80×80 | 3.0 / 4.0 / 5.0 | 7.31 / 9.56 / 11.73 |
| 100×100 | 3.0 / 4.0 / 5.0 / 6.0 | 9.21 / 12.09 / 14.91 / 17.66 |
| 120×120 | 3.0 / 4.0 / 5.0 / 6.0 | 11.11 / 14.62 / 18.06 / 21.43 |
| 150×150 | 4.0 / 5.0 / 6.0 / 8.0 | 18.32 / 22.68 / 26.98 / 35.34 |
Theoretical weight formula
Weight per meter (kg/m) = 0.02466 × (side length + side length – wall thickness × 2) × wall thickness × (1.03～1.06).
Zinc Coating Comparison Table for Different Standards
| Standard | Commonly used coating levels | Zinc coating weight (g/m²) | Zinc layer thickness (µm) | Notes |
|---|---|---|---|---|
| ASTM A123 / ISO 1461 | Hot-dip galvanized | ≥275 (total both sides) | ≥85 (local average) | Global standard for hot-dip galvanized steel structures |
| ASTM A653 / A1011 | G60 / G90 | ≥180 / ≥275 | ≥45 / ≥67 | Pre-galvanized sheet steel (for reference only) |
| EN 10346 / EN 10219 | Z275 | ≥275 | ≥67 | European standard for pre-galvanized sheets |
| GB/T 13912 / GB/T 6728 | Z275 | ≥275 | ≥67 | Chinese standard for hot-dip galvanized hollow sections |
| JIS G3302 / JIS G3466 | Z275 | ≥275 | ≥67 | Japanese standard for galvanized steel structures |
| AS/NZS 1365 | Z275 | ≥275 | ≥67 | Australian/New Zealand standard |
Material Description
Our hot-dip galvanized square and rectangular tubes use structural carbon and low-alloy steel as base material, ensuring excellent weldability, mechanical strength, and long-term durability for construction and engineering applications.
We offer a full range of grades complying with major international standards to meet different market and project requirements:
- Chinese standard: Q195, Q215, Q235(A/B), Q355(B/C/D/E), 20# seamless grade
- American standard: ASTM A500 Gr.B/Gr.C, ASTM A53 Gr.B, A36 – European standard: S235JR, S355JR (EN 10219)
- German standard: ST37
For general structural use, Q235B / ASTM A500 Gr.B / S235JR are the most common and cost-effective grades. For high-strength or load-bearing projects, we recommend Q355B / ASTM A500 Gr.C / S355JR.
Note: DX51D is a base material for pre-galvanized steel sheets, mainly used for pre-galvanized (post-forming) pipes. For hot-dip galvanized (post-welding) pipes, the structural steel grades listed above are used to ensure full zinc coating protection at welds and corners.
Zinc Coating Description
Z275 (equivalent to US standard G90) is an internationally recognized high-performance zinc coating designation, representing a total zinc coating weight of ≥275 g/m² on both sides.
Our hot-dip galvanizing process ensures a complete, uniform zinc coating on all surfaces, including welds and corners, providing far better corrosion resistance than pre-galvanized pipes. This makes Z275 the ideal choice for outdoor projects, coastal area structures, and heavily corrosive industrial environments.
Why Choose Us?
- Automated Production: Full-process intelligent equipment coverage ensures short delivery cycles, high dimensional accuracy, and batch consistency.
- Flexible Customization: Supports non-standard specifications; samples of irregular cross-sections/special zinc coatings are available within 72 hours; customized solutions have been provided to over 200 industries.
- Guaranteed Quality: 12 inspection processes from raw materials to finished products ensure zinc coating uniformity is 1.5 times higher than national standards; products have passed EU CE certification.
- High Cost-Effectiveness: Professional export services, factory direct sales, no middlemen. Flexible minimum order quantities for trial orders; supports FOB/CIF/CFR/Ex-Works and other trade terms.
FAQs
Glory Steel Factory, located in Tianjin, China, is an ISO 9001 certified factory with an annual output of 100,000 tons. We specialize in manufacturing GI steel pipes ranging from Z30 to Z275, including square, round, rectangular, and triangular pipes, as well as culverts, corrugated pipes, drainage pipes, gas pipes, and oil pipes. With high-quality products and services, our products are exported to over 120 countries.
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