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Help CenterSteel Pipe & Tube & Hot Galvanized Round Pipe，Q195、Q215A/B、Q235A/B、Q355B
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1. Product Overview
Hot-dip galvanized steel pipe, fully named hot-dip galvanized welded steel pipe, adopts low-carbon black welded pipe or seamless steel pipe as base material. It is immersed in molten zinc liquid at high temperature of about 500℃ to form zinc-iron alloy protective layer on both inner and outer pipe walls. Different from electro-galvanized pipe with thin coating and poor anti-corrosion performance, it is a long-term anti-corrosion pipe widely used in low-pressure fluid transportation, steel structure and fire protection projects, complying with domestic and international general engineering standards.
Applicable Standards
Domestic Standards: GB/T 3091-2015 Welded Steel Pipes for Low-pressure Fluid Transportation; GB/T 13912-2020 Metallic Coatings – Hot-dip Galvanized Coatings on Ferrous Articles – Specifications and Test Methods
International Export Standards: ASTM A53, BS 1387, EN 10240, ISO 65
2. Raw Material & Grades
The base material is high-quality low-carbon carbon steel with stable performance, easy welding, threading and bending processing:
Q195, Q215A/B: Small-diameter thin-wall pipes, greenhouse supports, cable conduits
Q235A/B (Main Grade): Fire protection, water supply & drainage, gas and steel structure projects, yield strength ≥235MPa, tensile strength 390~500MPa
Q355B: Thick-walled large-diameter pipes, heavy-duty supports, pipes for outdoor high-corrosion environments
3. Complete Production Process
Inspection of finished black pipes → Degreasing & Oil Removal → Clean Water Rinsing → Hydrochloric Acid Pickling for Oxide Scale Removal → Neutralization Cleaning → Flux Dipping → Preheating & Drying → Hot-dip Galvanizing (Immersion in zinc bath at 460~520℃) → High-pressure Air Blowing to Remove Excess Zinc Inside & Outside → Water Cooling → Chromium-free Passivation for Secondary Rust Prevention → Rinsing & Drying → Straightening, Pipe End Processing (Plain Cut / Threading / Beveling / Grooving) → Hydrostatic Pressure & Flaw Detection → Marking & Spraying Codes → Packing & Warehousing
4. Core Product Specifications & Technical Parameters
4.1 Diameter Range
Nominal diameter DN15 (1/2") ~ DN300 (12") with standardized outer diameter, divided into standard wall thickness and extra-heavy wall thickness (SCH40 / SCH80)
4.2 Wall Thickness Range
1.8mm ~ 10mm, national standard full size without negative tolerance
4.3 Standard Fixed Length
6 meters per piece normally; customized lengths of 3m, 5.8m, 9m, 12m available
4.4 Zinc Coating Technical Indicators (Mandatory National Standard)
Average zinc coating thickness ≥70μm, customized outdoor grade ≥85μm
Zinc coating weight per unit area ≥600g/㎡
Coating adhesion: No peeling or falling off after 180° bending; neutral salt spray resistance ≥1000 hours
Uniform galvanization on inner and outer walls, free of missing plating, zinc tumors, burrs and iron exposure defects
4.5 Pressure Bearing Performance
Hydrostatic test pressure 3.0MPa for DN15~DN168.3 small-diameter pipes
Hydrostatic test pressure 5.0MPa for DN177.8~DN323.9 large-diameter pipes
Normal working pressure ≤1.6MPa, suitable for low-pressure water, gas and air transportation
4.6 Optional Pipe End Treatments
Plain End: For welding and flange connection
Threaded End with Matching Couplings: Indoor water supply, drainage and fire protection threaded pipelines
Beveled End: Large-diameter welding projects
Grooved End: Special for fire protection clamp pipelines
5. Core Product Advantages
Excellent Long-term Anti-corrosion PerformanceThe zinc coating forms a physical isolation film. When the coating is damaged, zinc acts as a sacrificial anode to corrode preferentially and protect the steel substrate. Service life reaches 30~50 years indoors and over 20 years for outdoor underground burial. Its anti-corrosion life is 3~5 times that of electro-galvanized pipe, resistant to humid, saline-alkali and mild acid-base environments.
Uniform Coating with Strong AdhesionMetallurgically bonded zinc-iron alloy layer formed under high temperature, free of peeling and shedding. Inner wall is galvanized simultaneously to avoid pipe blockage caused by internal rust.
Excellent Mechanical PropertiesThe base material features high toughness, impact resistance and deformation resistance. It can be cut, welded, threaded, grooved and bent with strong construction adaptability.
Smooth Fluid TransportationSmooth inner wall without burrs, low fluid resistance and less scaling blockage. Passivation treatment meets environmental standards for drinking water transportation with non-toxic precipitation.
High Cost PerformanceLower procurement cost compared with stainless steel and plastic-coated anti-corrosion pipes, no frequent rust removal maintenance in later stage, reducing overall project cost.
Complete Specifications & Fast DeliveryFull stock of DN15-DN200 all specifications, shipped from Tianjin Port, production & delivery cycle 5-7 days. Customized size, zinc coating thickness and pipe end processing available for bulk truck orders.
6. Main Application Fields
Fire Protection Engineering: Sprinkler pipes, main fire hydrant pipelines, overhead & underground fire pipe networks
Municipal Water Supply & Drainage: Residential tap water delivery, rainwater drainage, municipal low-pressure water supply pipelines
Gas & HVAC: Civil gas transportation, heating steam pipelines, central air conditioning circulating water systems
Steel Structure & Infrastructure: Construction scaffolding, factory columns, photovoltaic brackets, highway guardrails, greenhouse frames
Power & Communication: Cable protection conduits with anti-collision and moisture-proof functions
Agricultural Irrigation: Farm water delivery pipes, breeding fences, greenhouse frames
Industrial Fluid: Compressed air, low-pressure oil, industrial clean water transportation pipelines
7. Inspection Standards & Factory Certificates
Full-item inspection for each batch with complete supporting documents:
Dimensional tolerance inspection (outer diameter, wall thickness, length)
Hydrostatic pressure resistance test, weld non-destructive flaw detection
Zinc coating thickness, adhesion and salt spray anti-corrosion test
Mechanical tensile and impact test of raw material
Factory certificate, material test report, SGS inspection report (for export)
8. Packaging, Marking & Logistics Delivery
Packaging: Bundled with steel strips in fixed quantity per bundle; plastic protective caps equipped for threaded pipes to prevent thread collision and rust
Marking: Each pipe printed with specification, DN nominal diameter, material grade, execution standard and manufacturer information; product labels attached to each bundle
Delivery: Direct shipment from warehouse, loading at Tianjin Port for 40HC high cube containers; delivery cycle 5-7 days, full truck and LCL export supported
9. Comparison: Hot-dip Galvanized Pipe VS Electro-galvanized Pipe
| Comparison Item | Hot-dip Galvanized Steel Pipe | Electro-galvanized Steel Pipe |
|---|---|---|
| Zinc Coating Thickness | 70~100μm, full coverage inside & outside | 10~30μm, extremely thin inner coating |
| Coating Adhesion | Metallurgical bonding, no zinc peeling after bending | Physical adsorption, easy peeling & shedding |
| Service Life | 20~50 years for outdoor use | 3~5 years indoor, rust within 1 year outdoors |
| Applicable Scenarios | Fire protection, municipal engineering, underground & outdoor projects | Temporary simple indoor supports, not recommended for fluid pipelines |
| Cost | Moderate, mainstream choice for engineering | Low price, unqualified anti-corrosion, prohibited in formal projects |
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