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Help CenterSteel Pipe & Tube & Galvanized Steel Pipe，Q195, ASTM A53 Gr.A/B, EN 10255, BS1387
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Hot-dip galvanized steel pipe, also known as galvanized welded steel pipe, refers to carbon steel pipe coated with a zinc layer on the surface for anti-corrosion and rust prevention and extended service life. Currently, hot-dip galvanized steel pipe dominates the market, while backward cold galvanized pipes have been basically phased out. It is a high-quality anti-corrosion steel pipe widely recognized in the industry.
1. Product Classification & Production Process
Hot-Dip Galvanized Steel Pipe (Mainstream Product): The steel pipe is pickled to remove surface oxide scale, then immersed in molten zinc liquid at 450–460℃ to form a composite layer of zinc-iron alloy and pure zinc with strong adhesion to the steel substrate. The zinc layer thickness is ≥55μm with a double-sided zinc coating weight of approximately 600g/㎡. This type of anti-corrosion steel pipe features a service life of 30–50 years under conventional indoor and outdoor environments.
Cold Galvanized Steel Pipe (Obsolete): Adopts electro-galvanizing technology with a thin and uneven zinc layer of only 10–50g/㎡, resulting in poor anti-rust performance. It is prone to rusting and has been officially prohibited for domestic use since 2000.
2. Material & Executive Standards
Product Material: Standard grade adopts Q235B carbon steel; Q355B low-alloy steel is available for high-strength working scenarios, featuring stable mechanical properties and reliable quality.
Executive Standards:
GB/T 3091-2025 Welded Steel Pipes for Low-Pressure Fluid Delivery, the national standard for universal fluid transmission pipes;
GB/T 13912-2022 Metallic Coatings — Hot-Dip Galvanized Coatings on Iron and Steel Articles — Specifications and Test Methods.
3. Core Specification Parameters (Common Sizes)
Common nominal diameter, outer diameter, wall thickness and unit weight parameters are listed below:
Nominal Diameter |
Outer Diameter (mm) |
Wall Thickness (mm) |
Unit Weight (kg/m) |
DN15 (1/2") |
21.3 |
2.75 |
1.35 |
DN20 (3/4") |
26.9 |
2.75 |
1.70 |
DN25 (1") |
33.7 |
3.25 |
2.41 |
DN40 (1.5") |
48.3 |
3.50 |
3.84 |
DN50 (2") |
60.3 |
3.80 |
4.88 |
DN80 (3") |
88.9 |
4.00 |
8.38 |
DN100 (4") |
114.3 |
4.00 |
10.85 |
The standard fixed length is 6 meters per piece. Custom lengths from 3 to 12 meters are available. All specifications of hot-dip galvanized steel pipes can be processed on demand.
4. Product Performance Features
Excellent Anti-Corrosion Performance: The zinc layer provides physical isolation and sacrificial anode protection. It remains rust-proof even with partial coating damage, making this anti-corrosion steel pipe far more durable than ordinary black steel pipes.
Ultra-Long Service Life: Requires no maintenance for 30–50 years in conventional atmospheric environments, 5–10 times the service life of ordinary pipes.
Stable Mechanical Properties: Inherits high strength of carbon steel with excellent pressure resistance, bending resistance and impact resistance, suitable for complex working conditions.
Elegant Appearance: Features uniform silver-white zinc spangles with a smooth surface, applicable for exposed installation.
High Cost Performance: One-time installation with long-term maintenance-free use, effectively reducing later operation and maintenance costs.
Easy Processing & Installation: Supports cutting, threading, bending and welding with low construction difficulty, serving as an ideal fluid transmission pipe.
5. Main Applications
Fire Protection Engineering: Applied for fire hydrant and sprinkler systems, serving as the preferred hot-dip galvanized steel pipe for fire engineering projects.
Low-Pressure Fluid Transmission: Used for conveying gas, air, oil, heating steam, sewage and other media, classified as standard fluid transmission pipes.
Building Structure: Widely used for scaffolding, steel structure supports, guardrails and equipment brackets.
Electrical Engineering: Serves as wire protection pipes with compression and corrosion resistance to ensure circuit safety.
Usage Restriction: This type of pipe has been prohibited for drinking water pipeline use since 2000 to avoid potential safety hazards caused by zinc ion precipitation.
6. Quality Inspection Standards
Visual Inspection: The hot-dip galvanized steel pipe surface shall be free of missing galvanization, black spots, peeling and defects with uniform zinc spangles.
Zinc Layer Thickness Test: Tested by magnetic thickness gauge, the zinc layer thickness shall be no less than 55μm to guarantee the basic anti-corrosion performance of anti-corrosion steel pipes.
Hydrostatic Pressure Test: Standard test pressure for ordinary fluid transmission pipes is 2.5MPa, and 3.0MPa for thickened pipes. Qualified products show no leakage and no pressure attenuation.
Bending Test: Pipes with DN≤50mm show no pipe cracking and no zinc layer peeling after 90-degree bending.
7. Installation & Maintenance
Connection Methods: Three mainstream connection modes are available: threaded connection, flange connection and welding, adapting to diverse engineering construction requirements.
Daily Maintenance: Hot-dip galvanized steel pipes require no additional paint protection under normal service environments. Cold spray zinc coating can be applied to repair welding joints and damaged coating areas to restore anti-corrosion performance.
8. Purchasing Guidelines
Prioritize qualified regular hot-dip galvanized steel pipes and reject inferior cold galvanized products with thin coatings and poor rust resistance.
Verify compliance with GB/T 3091-2025 national standard and strictly check pipe outer diameter, wall thickness and weight to avoid non-standard products.
Test zinc layer thickness and surface quality, and refuse unqualified anti-corrosion steel pipes and fluid transmission pipes with insufficient wall thickness and substandard coatings.
9. Delivery Cycle
In-Stock Orders: Sufficient inventory of full-specification hot-dip galvanized steel pipes, standard national-grade anti-corrosion steel pipes and general engineering fluid transmission pipes. Conventional in-stock orders will be delivered within 3–5 working days after payment.
Custom Processing Orders: Orders with customized fixed lengths (3–12m), threading, cutting and flange processing will be delivered within 5–7 working days.
Large-Batch Engineering Orders: Production schedule can be negotiated according to purchase quantity, with the fastest delivery within 5 working days.
Logistics Service: Supports full-truck delivery and express logistics with nationwide distribution and stable transit time to meet urgent engineering demands.
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