Galvanized Rectangular Tube ASTM A500 For Construction, Machinery & Municipal Engineering Usage

Our hot-dip galvanized rectangular tube, also known as galvanized rectangular hollow section (RHS), is a high-performance structural steel product manufactured by ERW (Electric Resistance Welding) technology and surface hot-dip galvanizing treatment. It is available in a wide range of specifications, with outer dimensions from 20×30mm to 300×500mm, wall thickness from 1.5mm to 16mm, and base material grades including Q235B, Q345B (GB/T 6728), ASTM A500 Gr B/C, and EN 10219 S235JRH/S355J2H. The product features excellent corrosion resistance, high structural strength, good processability, and wide adaptability, making it an ideal choice for structural support, framing, and decoration in construction, machinery manufacturing, municipal engineering, agricultural facilities, and other fields.

In many industrial and engineering scenarios, traditional steel rectangular tubes face inevitable problems that affect project safety and service life. First, ordinary black steel tubes lack effective anti-corrosion protection, and they are prone to rust and corrosion when exposed to outdoor environments, humid conditions or soil erosion, which shortens their service life and increases maintenance costs significantly. Second, some projects have strict requirements for structural stability and load-bearing capacity, while common steel tubes cannot balance strength and corrosion resistance, leading to potential safety hazards in long-term use. Third, the complexity of construction scenarios (such as outdoor, high humidity, and heavy load) requires materials to be easy to process, install, and customize, but traditional products often have limitations in processability and specification flexibility, which affects construction efficiency and project progress. In addition, the demand for environmental protection and cost control also makes it necessary to find a material that is durable, low-maintenance, and cost-effective, which traditional steel tubes cannot fully meet.

To solve the above problems, our hot-dip galvanized rectangular tube provides a comprehensive and reliable solution. First, we adopt the hot-dip galvanizing process, which immerses the formed rectangular tube into molten zinc, forming a dense zinc-iron alloy coating on the surface that is metallurgically bonded with the steel substrate—not just a simple surface attachment. This coating effectively isolates air, moisture, and corrosive media, increasing the anti-rust life by 3-5 times compared with ordinary black tubes, and reducing long-term maintenance costs. Second, the base material is selected from high-quality steel that meets national and international standards, and the rectangular cross-section design enhances bending and torsional strength, ensuring excellent load-bearing capacity and structural stability, which can meet the needs of different load scenarios from light decoration to heavy industrial structures. Third, we provide a complete range of standard specifications and flexible customization services, supporting the customization of special dimensions, wall thicknesses, and lengths, and can also provide additional processing services such as cutting, punching, and welding to adapt to various construction needs and improve construction efficiency. Finally, our products comply with environmental standards, the zinc coating is recyclable, and the overall cost performance is high, achieving a balance between project safety, durability, and cost control.

Steel Coil → Slitting → Forming → ERW Welding → Sizing → Cutting → Passivation → Packing

This continuous production ensures:

• Stable welding seam
• Accurate dimensions
• Consistent coating

The production and anti-corrosion principle of galvanized rectangular tube mainly includes two core links: ERW tube formation and hot-dip galvanizing, and its working mechanism is as follows:

1. ERW Tube Formation: First, the flat steel coil is unrolled and shaped into a rectangular profile through cold bending. Then, the edges of the profile are welded tightly using high-frequency electric resistance welding technology. After welding, the tube is sized, straightened, and cut to the required length to form a blank rectangular steel tube with a smooth surface and stable structure.
2. Hot-Dip Galvanizing Process: The blank rectangular tube undergoes a series of pre-treatments first: degreasing (removing oil stains on the surface), pickling (removing rust and oxide layers), water washing, flux dipping (preventing secondary oxidation and enhancing coating adhesion), and drying/preheating (removing residual moisture to avoid zinc explosion during galvanizing). Then, the pre-treated tube is immersed in molten zinc liquid (temperature controlled at an appropriate range) for a certain time. The zinc liquid adheres to the surface of the steel tube and forms a dense zinc-iron alloy layer through metallurgical reaction with the steel substrate—not just a simple surface attachment. Finally, after finishing, cooling, passivation, and inspection, the galvanized rectangular tube with a uniform and firm zinc coating is obtained.
3. Anti-Corrosion Mechanism: The zinc coating acts as a "protective coat" for the steel tube. On the one hand, it isolates the steel substrate from air, moisture, and corrosive media, preventing direct oxidation and corrosion of the steel. On the other hand, zinc has a higher electrode potential than iron. When the coating is slightly damaged, zinc will act as an anode to undergo oxidation reaction first, protecting the steel substrate from corrosion (cathodic protection), thus achieving long-term anti-rust effect.

• Packing (Bundles / Seaworthy Packaging)
• Tagging
• Weight Checking
• Trucking / Shipment