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Help CenterSteel Pipe & Tube & Hot Dipped Galvanized Steel Pipe，ASTM A53/A53M、BS1387、EN10240、JIS G3444
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1. Product Overview
Hot-dip galvanized steel pipe (hot-dip galvanized welded steel pipe) takes low-carbon straight seam welded pipe or seamless steel pipe as the base material. After complete hot-dip galvanizing anti-corrosion treatment, a dense zinc-iron alloy protective layer is formed on both inner and outer pipe walls. It is a general anti-corrosion pipe for engineering. Cold galvanizing (electro-galvanizing) has thin zinc coating and peels off easily, so it is prohibited for domestic water supply and gas pipelines. Our products only supply compliant hot-dip galvanized pipes.
Based on the sacrificial anode anti-corrosion principle of zinc coating, the pipe is isolated from air, water vapor, acid and alkali media to greatly extend the anti-rust service life of steel. It combines the structural strength of carbon steel and long-term anti-corrosion performance, suitable for indoor, outdoor, buried, humid and highly corrosive working conditions.
2. Implementation Standards
Domestic Standards
GB/T 3091-2025 Welded Steel Tubes for Low-Pressure Fluid Transportation (Main standard for fluid transportation, working pressure ≤1.6MPa)
GB/T 13912 Metallic Coatings - Hot-dip Galvanized Coatings on Steel Articles - Technical Requirements and Test Methods (Testing standard for galvanized coating)
International Export Standards
ASTM A53/A53M, BS1387, EN10240, JIS G3444. American, British and European standard specifications can be customized as required.
3. Base Material Grade
Main Grade: Q235B low-carbon carbon steel (general engineering, highest cost performance)
Optional Grades: Q195, Q215B (light thin-wall pipe), Q355B (thick-wall high-pressure, heavy-load structure)
Chemical Composition Control: C≤0.22%, Mn≤1.4%, S≤0.045%, P≤0.045%. Good ductility, supporting threading, grooving and welding processing.
Mechanical Properties: Yield strength of Q235B ≥235MPa; Yield strength of Q355B ≥355MPa with stable pressure bearing and bending resistance.
4. Complete Production Process
Black steel pipe base → Degreasing & Oil Removal → Clean Water Rinsing → Hydrochloric Acid Pickling for Oxide Scale Removal → Multi-stage Rinsing → Flux Activation (Mixture of Ammonium Chloride & Zinc Chloride) → Drying → Hot-dipping in Molten Zinc at 450℃±5℃ (1–2 minutes) → Internal & External Zinc Blowing for Thickness Control → Air Cooling & Water Cooling → Passivation & Sealing → Finished Product Inspection → Packaging & Warehousing
Synchronous internal and external galvanization, no missing galvanization or exposed substrate defects.
Passivation treatment improves the coating’s resistance to white rust, avoiding oxidation and whitening during storage.
5. Core Technical Indicators of Zinc Coating
Average zinc coating thickness ≥80μm, minimum local thickness ≥70μm
Zinc coating weight ≥640g/㎡; Heavy anti-corrosion customized version ≥850g/㎡
Strong coating adhesion: no peeling or shedding after hammering and bending tests
Anti-corrosion service life: 20–30 years under conventional dry environment; 10–20 years under outdoor humid environment; over 40 years with additional anti-corrosion coating for buried installation.
6. Specification Parameter System
6.1 Caliber Range
Nominal diameter DN15 (1/2") ~ DN300 (12"), corresponding outer diameter 21.3mm ~ 323.9mm
6.2 Wall Thickness Classification
Standard wall thickness: 2.0–6.0mm (civil water supply, fire protection conventional type)
Reinforced wall thickness: 6.0–10.0mm (high-pressure fluid, scaffolding structure)Wall thickness tolerance ±10%. Sch40/Sch80 thick-wall series can be customized for pressure-bearing pipelines.
6.3 Fixed Length
Standard length: 6 meters per piece; customized 9m, 12m available. Random fixed length from 6–12m and cutting processing are supported, length tolerance ±10mm.
6.4 Adaptable Connection Methods
Thread connection: DN15–DN50, household water supply and gas pipelines, matched with galvanized threaded fittings.
Grooved clamp connection: DN65–DN300, fire sprinkler and municipal pipe network, fast installation and anti-seismic.
Flange connection: DN100 and above for pump stations and low-pressure chemical transportation with excellent sealing performance.
Welding connection: Large-diameter structural supports and greenhouse frames; zinc coating shall be repaired after welding.
Standard National Specification Comparison Table
| Nominal DN | Inch | Outer Diameter (mm) | Standard Wall Thickness (mm) | Theoretical Weight (kg/m) |
|---|---|---|---|---|
| DN15 | 1/2" | 21.3 | 2.8 | 1.357 |
| DN20 | 3/4" | 26.9 | 2.8 | 1.760 |
| DN25 | 1" | 33.7 | 3.2 | 2.540 |
| DN50 | 2" | 60.3 | 3.8 | 5.290 |
| DN80 | 3" | 88.9 | 4.0 | 8.380 |
| DN100 | 4" | 114.3 | 4.0 | 10.85 |
7. Product Performance Testing Items
Hydrostatic Burst Test: Stable pressure at 2.5–5.0MPa without leakage, test pressure matched according to caliber.
Zinc Coating Thickness Test: Full sampling inspection by magnetic thickness gauge.
Adhesion Hammer Test: No zinc coating shedding after knocking with 5kg drop hammer.
Tensile, Flattening and Bending Mechanical Tests to ensure no cracking of base material.
Full appearance inspection: No missing galvanization, burrs, zinc tumors or holes.
8. Main Application Fields
Fire Protection Engineering: Fire hydrant pipe network, automatic sprinkler system (mandatory mainstream pipe for domestic fire protection).
Municipal Fluid Transportation: Low-pressure gas, industrial circulating water, heating pipeline.
Construction Engineering: Scaffolding, curtain wall keel, guardrail, structural support.
Agricultural Greenhouse: Greenhouse frame, farmland irrigation pipeline.
Electric Power & Communication: Cable protection conduit, street lamp support.
Industrial Plants: Low-pressure compressed air, slightly corrosive medium transportation.
9. Core Product Advantages
Long-lasting anti-corrosion: Double-layer zinc coating inside and outside to isolate rust and greatly reduce later maintenance cost.
Convenient processing: Available for threading, grooving, cutting and welding, matched with full series of galvanized pipe fittings.
Wide compatibility: Applicable for indoor, open-air and buried installation, resistant to mild acid, alkali and humidity.
Complete specifications: Cover small-caliber household pipes to large-caliber municipal pipes, non-standard customization supported.
Safe and stable: Compliant pressure bearing without leakage risk, meeting domestic fire protection and municipal acceptance standards.
Fast delivery: Sufficient spot inventory, shipped from Tianjin Port, production cycle 5–7 days.
10. Packaging, Marking & Transportation
Packaging: Standard 6m pipes bundled with steel strips, 50–100 pieces per bundle. Plastic protective caps installed at pipe ends to prevent collision damage to threads and pipe mouths during transportation.
Marking: Each bundle attached with qualification label marked with specification, material grade, implementation standard, furnace number and production date; permanent marks sprayed on pipe body.
Transportation: Truck or container sea transportation; rainproof packaging available to avoid white rust caused by moisture during sea freight.
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