Tianjin Brisk Metalwork Co., Ltd. is one of the leading manufacturers and suppliers of hot dip galvanized square hollow section in China. We have world-leading production equipment and strong manufacturing capabilities. Please feel free to buy bulk durable hot dip galvanized square hollow section from our factory.
Tianjin Brisk Steel is one of the manufacturers of Hot Dip Galvanized Square Hollow Section in China. Our products are mainly exported to the Middle East, Southeast Asia, Europe, New Zealand, and other regions.If you would like to learn more about our products, feel free to contact us and send your purchase list.
PRODUCT
Tianjin Brisk Steel focus on produce and supply hollow section and steel pipe
How Hot Dip Galvanizing Works
- Surface preparation – the finished square tube is degreased, then pickled in acid to remove rust and mill scale.
- Fluxing – a flux bath prevents oxidation and helps the zinc bond to the steel surface.
- Galvanizing bath – the tube is fully immersed in molten zinc, forming a series of zinc-iron alloy layers metallurgically bonded to the steel.
- Inspection – coating thickness, adhesion, and appearance are checked against the relevant standard before dispatch.
Because the coating forms through a chemical reaction rather than simple plating, it will not peel or flake under normal handling, and it continues to protect cut or drilled edges through galvanic (sacrificial) action.
Standards and Coating Thickness
Hot dip galvanized coatings on structural steel products are most commonly specified to one of the following standards:
- ASTM A123/A123M – the U.S. standard covering zinc coatings on rolled, pressed, and forged steel shapes, including structural tube. Coating thickness requirements are minimums, based on steel thickness category, and there is no maximum limit.
- EN ISO 1461 – the international/European standard for hot-dip galvanized coatings on fabricated iron and steel articles, commonly used across Europe, the Middle East, and parts of Asia.
Typical average coating thickness for structural square hollow section falls in the range of 45–85 microns, depending on base steel thickness - thicker steel sections retain heat longer in the zinc bath and generally develop a thicker coating.
Base Tube Specification
The underlying square hollow section is typically manufactured to a cold-formed structural tube standard before galvanizing, most commonly:
- EN 10219 S235JRH / S275J0H / S355J2H – cold-formed welded structural hollow sections (Europe)
- ASTM A500 Grade B/C – cold-formed welded carbon steel structural tubing (North America)
Common size range: 20×20 mm up to 400×400 mm outer dimension, with wall thickness from around 1.5 mm to 16 mm and standard lengths of 6 m, 12 m (custom cut lengths available on request).
Typical Applications
- Outdoor and agricultural structures – livestock sheds, greenhouses, fencing frames
- Highway and roadside infrastructure – guardrail posts, signage frames, noise barriers
- Solar mounting structures and ground-mount racking systems
- Marine and coastal construction where salt-air corrosion resistance is critical
- Carports, pergolas, and light structural steelwork exposed to weather
- Electrical transmission towers and substation structures
FAQ
Q: How long does a hot dip galvanized coating last?
A: Service life depends on coating thickness and the local environment. In typical rural or urban atmospheres, a standard hot-dip galvanized coating on structural steel commonly provides several decades of protection before first maintenance is needed; in coastal or industrial atmospheres, the corrosion rate is faster and service life is correspondingly shorter.
Q: Can hot dip galvanized square hollow section be welded on site?
A: Yes, but welding burns off the zinc coating in the heat-affected zone, leaving bare steel that is vulnerable to corrosion. Field welds are typically cleaned and repaired with a zinc-rich paint or a metallizing spray to restore corrosion protection.
Q: What sizes and wall thicknesses are available?
A: Standard production commonly covers outer dimensions from 20×20 mm to 400×400 mm, with wall thicknesses from about 1.5 mm to 16 mm. Exact availability depends on the mill's tube-forming and galvanizing bath capacity, so it's worth confirming size and length with the supplier for large or non-standard orders.
Q: What causes white rust on new galvanized steel, and is it a defect?
A: White rust (zinc oxide/zinc hydroxide) can form when freshly galvanized steel is stored in damp, poorly ventilated conditions, especially when tubes are stacked tightly together. Light surface white rust is usually a cosmetic issue rather than a structural one, but heavy or progressive white rust indicates poor storage and should be addressed with the supplier, since it can reduce coating life if left untreated.
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