40x80mm100x200mm Hot Dip Galvanized Rectangular Steel Tube For Heavy Load

Our Hot Dip Galvanized Rectangular Steel Tubes (RHS – Rectangular Hollow Sections) are engineered for applications requiring superior bending strength and load distribution compared to square or round tubes. Manufactured from high-strength Q235B / Q355B / S355JR steel, followed by a hot-dip galvanizing process according to ISO 1461 / ASTM A123, these tubes offer excellent corrosion resistance combined with optimized structural performance. The rectangular profile provides a higher moment of inertia, making it ideal for horizontal beams, trailer chassis, long-span roofing, and industrial machinery frames. Available in sizes from 40x80mm up to 100x200mm, with wall thicknesses ranging from 1.5mm to 6.0mm.

Key features:

• Higher load-bearing capacity per unit weight

• Optimal for long-span applications (reduces support points)

• Full hot-dip galvanized coating inside and out

• Excellent weldability and machinability

• Meets international structural steel standards

Many engineers default to square or round hollow sections for structural projects without considering the specific load direction. In applications where bending occurs primarily along one axis – such as roof purlins, trailer frames, crane runways, or mezzanine floors – square tubes often provide unnecessary strength in the vertical direction while lacking depth in the bending plane. Round tubes, on the other hand, are inefficient for beam applications due to their lower section modulus. Additionally, ordinary non-galvanized rectangular tubes suffer from rapid corrosion in outdoor or humid environments, especially at weld joints and cut ends, leading to costly maintenance and potential structural failure.

Our solution is the hot-dip galvanized rectangular hollow section – specifically designed to address the limitations of other profiles. The elongated shape provides a deeper section in the plane of bending, significantly increasing the moment of inertia and section modulus. This translates to higher bending resistance with less steel weight, reducing both material and shipping costs. The hot-dip galvanizing process coats every surface – internal and external – creating a robust barrier against rust. The zinc-iron alloy layer bonds metallurgically to the base steel, offering cathodic protection that lasts for decades. Whether you are building a heavy-duty trailer, a solar carport, or an industrial mezzanine, our galvanized rectangular tubes deliver superior strength and longevity.

Note: Custom sizes, thicknesses, and higher zinc coating can be produced upon request.

Due to their optimized bending strength, our galvanized rectangular tubes are the preferred choice for:

• Heavy-duty trailer & truck chassis – main rails and cross members

• Industrial mezzanine floors – primary and secondary beams

• Solar tracking structures – long-span torque tubes

• Building roof purlins & girts – warehouse and factory roofs

• Bridge railings & highway crash barriers – high impact resistance

• Agricultural equipment – large greenhouse frames, animal housing structures

• Shipping container frames & modification projects

• Crane runways & gantry beams

Galvanizing process – The rectangular tubes undergo a multi-stage cleaning (degreasing, pickling, fluxing) before being immersed in a 550°C molten zinc bath. The zinc reacts with the steel to form layered zinc-iron alloys, then a pure zinc outer layer. The tube is slowly withdrawn to ensure uniform coating on inner and outer surfaces, then cooled and inspected.

Mechanical advantage – For a given cross-sectional area, a rectangular tube has a greater depth-to-width ratio. When the longer side is oriented vertically (or in the bending direction), the section modulus increases sharply. This means a 100x200mm rectangular tube can resist significantly more bending load than a 150x150mm square tube of the same wall thickness and weight, while offering a lower overall height if needed.

To select the optimal galvanized rectangular tube for your application, follow these guidelines:

Identify the primary load direction – Determine which axis will bear the bending stress. Orient the longer side of the rectangle along the direction of the load for maximum strength. For horizontal beams (e.g., roof purlins), the longer side should be vertical.

Calculate required section modulus – If you have engineering specifications, match the required section modulus (Sx or Sy) to our tube dimensions. For non-engineered projects, use these rules of thumb:

• Light mezzanine / walkway: 40x80mm x 2.0mm (span ≤ 2m)
• Trailer chassis main rail: 100x200mm x 4.0mm
• Solar mounting beam: 60x120mm x 2.5mm
• Industrial racking beam: 80x140mm x 3.0mm

Consider environmental severity – Standard galvanizing (45-65µm) suits most inland environments. For coastal or chemical plant use, specify 75-90µm coating.

Check fabrication compatibility – All our tubes are weldable and drillable. However, welding will remove zinc locally – use zinc-rich touch-up paint after welding. Avoid galvanizing after welding if possible, as trapped gases may cause issues.

Length & tolerance – Longer spans (up to 12m) reduce on-site joining. Confirm straightness tolerance (typically 1mm per meter) before ordering.

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