20x20mm-200x200mm Hot Dip Galvanized Square Tube For Construction & Fencing

Our Hot Dip Galvanized Square Steel Tubes are manufactured from high-grade Q195, Q235B, or Q355B steel, followed by a strict hot-dip galvanizing process in compliance with ISO 1461. The result is a strong, corrosion-resistant square tube suitable for both indoor and outdoor applications. Available in sizes from 20x20mm up to 200x200mm, with wall thicknesses ranging from 1.0mm to 5.0mm. These tubes offer excellent weldability, straightness, and a smooth zinc-coated surface, making them a reliable choice for structural, agricultural, and industrial projects.

Key features:

• Full zinc coating inside and out

• Excellent anti-rust performance (15+ years outdoor service)

• High strength-to-weight ratio

• Easy cutting, welding, and drilling

• Cost-effective compared to stainless steel

In many construction and infrastructure projects, ordinary black steel tubes are used without proper corrosion protection. Over time, especially in humid, rainy, or coastal environments, these tubes begin to rust rapidly. Rust not only affects appearance but also weakens structural integrity, leading to safety risks, frequent maintenance, and premature replacement. Painting or powder coating alone often fails due to scratches, moisture penetration, or poor adhesion, causing hidden corrosion underneath the surface. As a result, project owners face higher long-term costs and unexpected downtime.

Our solution is the hot-dip galvanized square steel tube. Unlike ordinary painted or pre-galvanized tubes, hot-dip galvanizing immerses the entire steel tube into molten zinc at approximately 550°C, forming a metallurgical bond between the zinc and the steel. This creates three protective layers: a zinc-iron alloy layer, a pure zinc layer, and a passive oxide film. This coating provides both barrier protection and cathodic protection – even if the surface is scratched, the surrounding zinc sacrifices itself to prevent the exposed steel from rusting. By choosing our galvanized square tubes, you eliminate the need for frequent repainting, reduce life-cycle costs, and ensure your structure remains safe and durable for decades.

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

Our hot-dip galvanized square tubes are widely used in:

• Steel structures & building frames – columns, beams, trusses

• Fencing & guardrails – highway barriers, garden fences, farm enclosures

• Solar mounting systems – ground and rooftop solar panel brackets

• Agricultural equipment – greenhouses, livestock pens, irrigation supports

• Transportation – trailer frames, bus shelters, sign posts

• Industrial shelving & racking – warehouses and workshops

• Decorative & architectural – handrails, awnings, street furniture

Surface preparation – The square tubes are degreased, pickled in acid to remove rust and mill scale, then rinsed and fluxed to ensure proper zinc adhesion.

Hot-dip galvanizing – The prepared tubes are slowly immersed into a bath of molten zinc at around 550°C. The zinc reacts with the steel surface to form a series of zinc-iron alloy layers.

Cooling & inspection – After a controlled withdrawal, the tubes are air-cooled or quenched, then inspected for coating uniformity, thickness, and appearance.

Final result – A metallurgically bonded, uniform coating is formed on both the exterior and interior surfaces, providing long-term corrosion protection that lasts decades in most environments.

How To Choose (Selection guide)

1. Load requirements – For light-duty applications (fencing, decoration), choose smaller sizes (20x20mm – 40x40mm) with thinner walls (1.0mm – 2.0mm). For structural or heavy loads (building frames, solar racks), choose larger sizes (60x60mm – 150x150mm) with thicker walls (2.5mm – 5.0mm).

2. Environmental conditions – In mild indoor environments, standard zinc coating (40-60µm) is sufficient. In highly corrosive environments (coastal areas, chemical plants, high humidity), request higher zinc coating (≥70µm) or additional passivation.

3. Fabrication method – If you plan to weld, cut, or drill, ensure the material is suitable for post-treatment. Our Q235B galvanized tubes offer good weldability; however, note that welding may burn off zinc locally, requiring touch-up with zinc-rich paint.

4. Length & tolerance – Confirm the required cut length and straightness tolerance with your supplier. Standard length is 6 meters, but custom lengths are available.

5. Certification – For export projects, request mill certificates and test reports showing compliance with ASTM A123, EN 1461, or local standards.

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