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Help CenterSteel Pipe & Tube & Hot Dipped Galvanized Steel Pipe，ASTM A53 Gr.A/B、EN 10255、BS1387、JIS G3452
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1. Product Definition & Executive Standards
1.1 Full Product Name
Low-pressure Fluid Transportation Hot-Dipped Galvanized Welded Steel Pipe. It adopts straight-seam welded steel pipe or seamless steel pipe as the base material with overall internal and external hot-dip galvanized anti-corrosion treatment.
1.2 Core Executive Standards
National Standard: GB/T 3091-2025 (Low-pressure Fluid Transportation Welded Steel Pipe), GB/T 13912 (Specification for Hot-Dip Galvanized Coatings)
Material Standard: GB/T 700 (Carbon Structural Steel)
International Standards: ASTM A53 Gr.A/B, EN 10255, BS1387, JIS G3452
2. Base Material & Mechanical Properties
2.1 Common Steel Grades
General Fluid Pipe: Q235B (mainstream), Q215A/B
High-strength Structural & Thick-walled Pressure Pipe: Q355B
Light-duty Small Pipe: Q195
2.2 Mechanical Indexes (Q235B)
Yield Strength (Rel): ≥235MPa
Tensile Strength (Rm): 370~500MPa
Elongation after Fracture: ≥21%
Excellent performance in bending, threading and welding processing
2.3 Hydrostatic Test Standard
DN15~DN168.3: Pressure holding at 3.0MPa without leakage
DN177.8~DN323.9: Pressure holding at 5.0MPa without leakage
3. Production Process & Coating Technical Parameters
3.1 Complete Production Process
Black pipe inspection → Degreasing & Deoiling → Fresh water rinsing → Hydrochloric acid pickling & derusting → Neutralization cleaning → Flux impregnation (ammonium chloride + zinc chloride) → Drying & preheating → Hot dipping in molten zinc solution at 455±5℃ for 30~120 seconds → Internal & external zinc blowing & leveling → Water cooling & passivation → Washing & air drying → Surface finishing → Hydrostatic/coating inspection → Marking, bundling & warehousing
3.2 Core Galvanized Coating Parameters (National Standard Mandatory)
Coating Structure: Inner zinc-iron alloy layer + outer pure zinc layer with metallurgical bonding (non-physical adhesion)
Zinc Coating Weight: Standard grade ≥300g/㎡; Heavy anti-corrosion customized grade ≥500g/㎡
Zinc Coating Thickness: Average ≥65μm, single point minimum ≥55μm; engineering thickened grade 70~100μm
Anti-corrosion Mechanism: Sacrificial anode protection. The zinc layer corrodes preferentially when scratched locally, protecting the steel pipe substrate from rusting
3.3 Appearance Characteristics
Uniform silver-gray surface with natural zinc spangles. A small amount of tiny zinc tumors and zinc slag on local areas are normal process phenomena. The internal and external pipe wall coatings are complete and uniform without missing plating, peeling or large-area shedding.
4. Complete Specification Parameters
4.1 Nominal Diameter Range
DN15 (1/2 inch) ~ DN300 (12 inches), covering civil, fire protection and municipal full-scenario applications
4.2 Standard Outer Diameter Comparison Table (Commonly Used)
Nominal Diameter (DN) |
Outer Diameter (mm) |
Standard Wall Thickness (mm) |
Thickened Wall Thickness (mm) |
|---|---|---|---|
15 |
21.3 |
2.75 |
3.25 |
20 |
26.8 |
2.75 |
3.50 |
25 |
33.7 |
3.25 |
4.00 |
32 |
42.4 |
3.25 |
4.00 |
40 |
48.3 |
3.50 |
4.25 |
50 |
60.3 |
3.80 |
4.50 |
65 |
76.1 |
4.00 |
4.75 |
80 |
88.9 |
4.00 |
5.00 |
100 |
114.3 |
4.00 |
5.00 |
150 |
168.3 |
4.50 |
6.00 |
200 |
219.1 |
6.00 |
8.00 |
4.3 Standard Length
Regular factory fixed length: 6 meters per piece. Custom lengths of 3m, 4m, 9m and 12m are available with on-demand cutting service. The galvanized weight gain coefficient ranges from 1.028 to 1.064 with wall thickness variation. Weight calculation formula: Theoretical weight of black pipe × galvanized weight gain coefficient
5. Core Product Advantages
Superior Durable Anti-corrosion PerformanceSalt spray resistance test: no red rust after 1000+ hours. Service life: 20~50 years in dry indoor environments, 8~15 years in buried/coastal humid environments. Its anti-corrosion capacity is 3~5 times that of cold galvanized (electro-galvanized) pipes.
Ultra-strong Coating AdhesionNo large-area coating peeling after 180° cold bending, knocking, threading and grooving processing. Only slight local zinc loss occurs after collision with easy repair.
Full-bore Internal & External ProtectionThe inner wall of the steel pipe is synchronously galvanized, effectively preventing scaling and rust blockage during fluid transportation, suitable for long-term delivery of water and gas media.
Diversified Installation AdaptabilityCompatible with four mainstream connection methods: threaded connection, grooved clamp connection, flange connection and welding connection, with complete supporting galvanized pipe fittings for convenient construction.
Stable Pressure Resistance & Compliance SafetyComply with acceptance specifications for fire protection, gas and municipal water supply & drainage projects. Specially recommended for outdoor, buried and open-air steel structure projects.
Low Full-life Cycle CostHigher initial procurement cost than cold galvanized pipes, but almost no later rust removal and painting maintenance cost, resulting in lower comprehensive project cost.
6. Four Main Connection Methods & Applicable Scenarios
Threaded ConnectionApplicable for small pipes ≤DN100, indoor water supply and fire protection branch pipes. Standard pipe threads are processed at pipe ends and sealed with raw material tape.
Grooved (Clamp) ConnectionApplicable for medium and large-diameter pipes ≥DN80, fire sprinkler systems and HVAC main pipelines. It causes no damage to the zinc coating, features convenient disassembly and assembly and excellent seismic performance, serving as the first choice for engineering projects.
Flange ConnectionApplied for connection with water pumps, valves, equipment and positions requiring frequent maintenance, with stable pressure bearing via flange gasket sealing.
Welding ConnectionSuitable for structural supports and large-diameter buried pipelines. Welding will damage the high-temperature zinc coating, so weld seams must be repainted with zinc-rich primer for secondary anti-corrosion treatment.
7. Main Application Fields
Fire Protection Engineering: Indoor and outdoor fire hydrants, automatic sprinkler systems, fire pump room main pipelines (designated pipes by construction specifications)
Fluid Transportation: Municipal cold water supply, heating steam, gas, industrial low-pressure oil & water, agricultural irrigation
Power & Communication: Cable protection conduits, outdoor power transmission tower frames, photovoltaic supports
Steel Structure Infrastructure: Greenhouse frames, factory guardrails, construction scaffolding, municipal bridge supports
Chemical & Coal Industry: Factory low-pressure medium transportation, underground ventilation, anti-corrosion support structures
8. Installation, Laying & Maintenance Guidelines
8.1 Buried Laying
Lay 100mm fine sand at the bottom of the pipe trench, remove hard stones during backfilling to avoid scratching the zinc coating. Wrap anti-corrosion adhesive tape for enhanced protection in corrosive soil environments.
8.2 Overhead Laying
Set fixed supports in accordance with specifications and control support spacing reasonably. Install insulation layers for high-temperature steam pipelines to reduce accelerated oxidation of the zinc coating.
8.3 Daily Maintenance
Minor exposed iron caused by collision: Polish and clean the surface, then apply zinc-rich repair paint.
Long-term immersion in strong acid and strong alkali high-corrosion media is prohibited.
Inner-lined plastic hot-dip galvanized composite pipes are recommended for drinking water transportation to reduce zinc ion precipitation.
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