Square/hot-dip Galvanized Steel Pipe

Hot-Dip Galvanized Square / Rectangular Steel Pipe (short for HDG SHS/RHS hollow section) is cold-formed ERW welded hollow structural steel tube, processed by full hot-dip galvanizing anti-corrosion treatment after pipe forming.

Different from black bare square tubes, molten zinc reacts with steel substrate to form a multi-layer zinc-iron alloy protective film, providing long-term cathodic anti-rust protection even in high-humidity pharmaceutical, food cleanrooms and outdoor factory environments. Flat right-angle surfaces simplify cutting, drilling, bolting and welding, making it the mainstream structural support material for purification engineering, HVAC and industrial frame projects.

Two core types:

1. Square Pipe (SHS): Equal side square hollow tube, uniform load-bearing, for vertical support columns, upright keels

2. Rectangular Pipe (RHS): Unequal side rectangular hollow tube, better bending resistance, for horizontal cross beams, ceiling hangers, equipment brackets

1. Manufacturing & Hot-Dip Galvanizing Process

1. Raw hot-rolled steel coil cold rolled & formed into square/rectangular blank

2. HF high-frequency ERW longitudinal welding, internal/external burr removal & stress relief

3. Pre-treatment: Pickling to remove rust, flux activation

4. Immerse into 450℃ molten zinc tank for hot-dip galvanizing

5. Air cooling, surface finishing, zinc layer thickness inspection

6. Fixed-length cutting, end deburring, bundling packaging

2. Base Steel Material & Global Standards

Steel Grades

• Q195 / S195: Light load indoor auxiliary brackets

• Q235B / S235JR / ASTM A500 Gr.B: Standard cleanroom support frame (most popular)

• Q355B / S355JR / ASTM A500 Gr.C: Heavy load long-span ceiling beams, outdoor heavy-duty structures

Certified International Standards

• Hollow section: ASTM A500, EN 10219, JIS G3466, GB/T 6728

• Hot-dip galvanizing: ASTM A123, EN ISO 1461, GB/T 13912

3. Size Range Specifications

Square Pipe (SHS)

• Side size: 20×20mm ~ 600×600mm

• Wall thickness: 1.0mm ~ 20mm

Rectangular Pipe (RHS)

• Dimension: 20×30mm ~ 400×700mm

• Wall thickness: 1.0mm ~ 20mm

Pipe End Treatment

Plain flat cut standard; optional deburred, chamfered ends for cleanroom on-site assembly

4. Hot-Dip Zinc Coating Key Parameters

• Standard zinc coating weight: 220–300g/m² (80–120μm thickness) for indoor cleanroom use

• Heavy anti-corrosion upgrade: 400–500g/m² (140–200μm) for high-humidity food/dairy workshops, outdoor factory frames

• Alloy layer structure: Zinc + zinc-iron intermetallic layers, scratch & abrasion resistant, no easy peeling during cutting/welding