Description
Factory-direct supply with in-house zinc testing — every Q235B galvanized square and rectangular steel tube is measured by coating thickness gauge before loading, ensuring Z30 to Z275 consistency per shipment.
Technical Specifications
| Parameter | Value |
|---|---|
| Designation | Q235B Galvanized Square and Rectangular Steel Tube |
| Product Type | Galvanized Square and Rectangular Steel Tube (GI Pipe / Hollow Section) |
| Steel Grade | Q195, Q215, Q235, Q345, 10#, 20#, 45#, 16Mn, ASTM A53 (Grade A/B), St37, St42, St52 |
| Standard | BS, EN, GB, AISI, ASTM, DIN, JIS |
| Section Shape | Square / Rectangular |
| Size Range | 10 mm – 1000 mm |
| Wall Thickness | 0.6 mm – 28 mm |
| Length | 1 m – 12 m |
| Technique | ERW (Hot Rolled / Cold Rolled) |
| Surface Treatment | Hot-Dip Galvanized (Zinc Coating 30–275 g/m²); also Bare, Oiled, Color Painted, 3PE |
| Tolerance | ±1% |
| Ends | Plain / Beveled / Threaded with Couplings or Sockets |
| Application | Steel structures / Building frames / General engineering / Machinery / Bridges / Ships / Boilers and pressure vessels / Industrial structures |
| MOQ | 1 Ton |
| Origin | Shandong, China |
Application Suitability
| Industry | Typical Applications |
|---|---|
| Construction & Steel Structures | Building frames, scaffolding systems, column bracing, roof trusses |
| Industrial & Machinery | Equipment frames, conveyor structures, industrial platforms, machine bases |
| Infrastructure & Bridges | Bridge railings, support piers, shipping container frames, industrial facility frameworks |
Zinc Coating Uniformity Is the Real Cost Driver on Galvanized Hollow Sections
Uneven zinc thickness means premature rust at weld seams and corners — the first place inspectors check.
I have seen containers of galvanized tubes rejected at destination because the coating measured 38 μm on the flat face but dropped below 20 μm near the corners. The supplier claimed “average Z275” on the certificate, but corner coverage was never verified. For a Q235B galvanized square and rectangular steel tube, the hot-dip process must account for zinc drainage at edges and internal corners — otherwise the thinnest spots corrode first. [NEED_CITE: hot-dip galvanizing coating thickness requirements for structural hollow sections] When your project specifies Z275, every measurement point — not just the average — must meet the threshold.
Matching Galvanized Hollow Sections to Corrosive Environments
A Q235B galvanized square and rectangular steel tube with Z275 coating serves coastal construction and industrial facilities where salt spray or chemical exposure demands long-term corrosion protection. The ERW welding process produces a smooth seam that accepts uniform zinc adhesion, while the ±1% dimensional tolerance ensures predictable fit-up on site. For interior or dry environments, Z30 or Z60 coatings reduce cost without sacrificing service life — but the choice must be made at inquiry stage, not after production. Our 2,800+ specification range covers side lengths from 10 mm to 1000 mm and wall thicknesses up to 28 mm, allowing engineers to select the exact profile without compromising on zinc class.
Engineering Compliance and Certification Requirements
Structural applications demand that Q235B galvanized square and rectangular steel tubes comply with dimensional and mechanical standards — EN 10219 for cold-formed sections in Europe, ASTM A500 or A53 for North American projects, and GB/T 6728 for domestic Chinese specifications. [NEED_CITE: EN 10219 cold-formed structural hollow section dimensional tolerances] The CE mark under EN 10210/10219 is mandatory for EU customs clearance, while SGS or BV third-party inspection reports satisfy regulated-market buyers in the Middle East and Southeast Asia. Wall thickness tolerance of ±1% ensures that theoretical weight invoicing aligns with actual delivered mass, preventing disputes at project handover. Custom end treatments — plain, beveled, or threaded with couplings — allow direct integration into bolted or welded connections without secondary machining.
Steel Grade Selection and ERW Process Fundamentals
Q235B remains the dominant grade for general structural use in China, offering adequate yield strength for building frames and scaffolding at competitive cost. For heavier loads, Q345 (equivalent to S355JR in EN standard) provides higher yield strength without increasing section size. The ERW (Electric Resistance Welding) process forms the tube from hot-rolled or cold-rolled coil, producing a longitudinal seam that is forge-welded under pressure — resulting in a homogeneous weld zone suitable for hot-dip galvanizing. Unlike seamless tubes, ERW galvanized hollow sections offer cost efficiency for non-pressure applications while maintaining dimensional accuracy across the 10 mm to 1000 mm size range. Hot-dip galvanizing immerses the finished tube in molten zinc at approximately 450°C, creating a metallurgical bond with the steel substrate that provides cathodic protection even if the coating is scratched. [NEED_CITE: steel grade equivalence between GB Q-series and EN S-series standards]
Hidden Costs of Incorrect Zinc Specification and Grade Mismatch
Ordering Q235B when the structural engineer specified Q345 means the tube may fail load testing — and replacement costs include not just the material but demolition and reinstallation. Similarly, accepting Z60 coating for a coastal facade project that requires Z275 accelerates corrosion at cut edges and weld points, leading to maintenance calls within the first year. [NEED_CITE: consequences of incorrect steel grade substitution in structural applications] Missing CE documentation blocks EU customs clearance, stranding the entire container at port while demurrage charges accumulate. These are not theoretical risks — they are recurring pain points we address through in-house testing, full certification packages, and professional export loading.
Why Procurement Teams Choose Xin Jiyuan for Galvanized Hollow Sections
Our factory operates three dedicated production lines covering over 2,800 specifications, including wall thicknesses up to 28 mm — eliminating the need to source thin-gauge decorative tubes and heavy structural sections from separate suppliers. The in-house physical and chemical laboratory tests every batch for zinc coating thickness using magnetic induction gauges, ensuring Z30, Z60, Z120, or Z275 compliance before release. We hold 41 invention patents including China’s original sharp-corner rectangular tube technology, providing architectural-grade aesthetics for facade applications. Full international certifications — ISO 9001:2015, Lloyd’s CE (EN 10210/10219), Singapore FPC, and SGS/BV verification — support customs clearance across 50+ export destinations. Custom non-standard sizes, cut-to-length service, and professional container loading with anti-damage measures protect the galvanized surface during ocean freight.
Documentation & Compliance
- Mill test certificate documenting Q235B chemical composition (C, Mn, Si, P, S) and yield strength per GB/T 700
- CE certificate confirming compliance with EN 10219 cold-formed structural hollow sections for EU market access
- ISO 9001:2015 quality management certificate covering production process and inspection procedures
- SGS or BV third-party inspection report verifying zinc coating thickness (Z30–Z275) and dimensional tolerance
- Material traceability by heat number linking each bundle to its original coil and galvanizing batch
- Export customs documents including packing list, bill of lading, and certificate of origin
Packaging, Loading & Delivery
- Q235B galvanized square and rectangular steel tubes bundled with steel strips and edge protectors to preserve zinc coating during transit
- Plastic end caps installed on all tube openings to prevent internal corrosion and debris accumulation
- Container loading optimized for 1 m – 12 m lengths with anti-shift bracing to prevent surface scratches
- Heat number and steel grade markings stenciled on each bundle for site identification and traceability
- FOB, CIF, or DDP shipping terms available with full export documentation and tracking until arrival
- Custom cutting and beveling service available for 1 m – 12 m lengths to reduce on-site fabrication waste
Ready to Verify Coating Quality Before You Order
Submit your Q235B galvanized square and rectangular steel tube specifications — including side length, wall thickness, zinc coating class, and destination port — to receive a detailed quotation with mill test certificate preview. We confirm coating thickness compliance, certification availability, and container loading plan before production begins.
Request Quotation with Zinc Coating Verification
Send your specifications to admin@sdxjypipe.com or contact us via WhatsApp at +86 188 5315 7756 for technical consultation and pricing.
Frequently Asked Questions
Q: What zinc coating options are available for Q235B galvanized square and rectangular steel tubes?
A: Hot-dip galvanizing is available in Z30, Z60, Z120, and Z275 classes (30–275 g/m²). Z30 suits interior or dry environments, while Z275 provides heavy-duty corrosion protection for coastal or industrial applications. Each coating class is verified by magnetic thickness gauge before shipment.
Q: Can you supply Q235B galvanized tubes with CE certification for EU projects?
A: Yes. Our Q235B galvanized square and rectangular steel tubes carry CE marking under EN 10210/EN 10219, supported by Lloyd’s Register certification. Mill test certificates and third-party inspection reports (SGS/BV) are provided for customs clearance.
Q: What is the minimum order quantity for custom sizes?
A: The standard MOQ is 1 Ton. Custom non-standard sizes within the 10 mm – 1000 mm side length and 0.6 mm – 28 mm wall thickness range are available with typical production lead times for non-stock specifications.
Q: How are galvanized tubes packed to prevent zinc coating damage?
A: Tubes are bundled with steel strips and fitted with edge protectors and plastic end caps. Container loading uses anti-shift bracing to prevent movement during ocean freight, preserving the galvanized surface finish.
Q: Can you provide mill test certificates showing chemical composition and mechanical properties?
A: Yes. Every shipment includes a mill test certificate documenting Q235B chemical composition (C, Mn, Si, P, S) and mechanical properties per GB/T 700. Third-party inspection by SGS or BV is available upon request before loading.
