Hot Dip Galvanized S355 Hollow Section

Tianjin Brisk Metalwork Co., Ltd. is one of the leading manufacturers and suppliers of hot dip galvanized s355 hollow section in China. We have world-leading production equipment and strong manufacturing capabilities. Please feel free to buy bulk durable hot dip galvanized s355 hollow section from our factory.

Our Product

Tianjin Brisk Steel focus on produce and supply hollow section and steel pipe

We tell customers about three effects, because each one shows up later on a fabrication floor or a site:

• Toughness change in cold-formed corners. Cold forming leaves strained steel at the corners of an SHS or RHS. Holding that steel in molten zinc can accelerate strain ageing and lower its impact energy. Impact values on the original MTC therefore describe the tube before galvanizing.
• Release of forming stress. Rolled and welded tube carries residual stresses. Heat can release them unevenly, and a long, thin-walled member may bow or twist during dipping.
• Zinc-steel reaction. The silicon and phosphorus in the steel change how fast zinc grows on the surface, so the coating can come out thick and dull grey or thin and bright.

All three are manageable if they are planned before production. None can be repaired after the tube has been dipped.

1. We nominate heats by silicon and phosphorus range before we roll, so the coating comes out even and within the ISO 1461 thickness category.
2. We recommend the right base tube for the service. For thick-wall or fatigue-loaded members, we suggest hot-finished EN 10210 or normalized tube, which has no cold-worked corner to age. For light and medium walls, cold-formed EN 10219 S355J2H performs well.
3. We choose a generous corner radius on request for heavy-wall cold-formed SHS/RHS, to reduce corner strain.
4. We check straightness again after galvanizing, not only before it. Tubes above our limit are cold-straightened before bundling.
5. We confirm venting and drain holes with you before production. Enclosed hollow sections must vent air and let zinc flow in and out, or the tube is a safety risk in the kettle. We mark hole positions on your drawing and drill to the agreed layout.
6. After-galvanizing Charpy testing is available on the same lot, when your specification needs proof that impact values remain acceptable once the coating is applied.

We galvanize to EN ISO 1461, where the required minimum coating thickness rises with steel wall thickness. For the wall thicknesses most common in S355 structural tube (6 mm and above), the standard requires a mean of at least 85 microns. Our delivered coatings typically run higher than the minimum, because S355 grades tend to react actively with zinc.

Our inspection gates before release:

• Visual check - continuous coating, no bare spots, no lumps, no ash inclusions
• Magnetic thickness gauge - readings taken on all faces, at a defined number of points per tube
• Adhesion check - coating must not flake under standard tap and cutting tests
• Straightness re-check after cooling
• Inside coating check at the ends and through the vent holes
• Coating report per lot, delivered with the EN 10204 3.1 tube certificate

Coating adds mass, and we tell you how much. On a 100 x 100 x 5 mm SHS with roughly 90 microns of zinc inside and outside, the coating adds about 0.5 kg per metre (roughly 3.4% on a 14.2 kg/m tube). Use this figure for freight and structural load checks.

• Rural and urban outdoor - typical service life of several decades before first maintenance.
• Coastal and industrial - a shorter but still long life, and we recommend adding a duplex paint system over the zinc for the harshest sites.
• Buried or immersed - please tell us the soil or water conditions; we advise on coating thickness and additional protection.
• Interior structures - galvanizing is rarely needed and a black finish is more economical.

A steel contractor building maintenance gantries at a coastal port specified 150 x 150 x 8 mm S355J2H SHS, hot dip galvanized. The specification also required Charpy impact values to remain at least 27 J at -20 degC after galvanizing, and a coating mean above 85 microns.

We supplied 96 lengths x 12 m (1,152 m, about 39.6 tonnes at 34.4 kg/m):

• Heat selection by silicon range before rolling
• Three Charpy sets tested after galvanizing: results from 58 to 74 J at -20 degC
• Coating mean of 118 microns across all tubes, with the lowest single reading at 92 microns
• Straightness re-checked after dipping: 3 of 96 tubes exceeded our limit and were cold-straightened before loading
• Delivery from order confirmation to loading port: 36 days

The contractor's inspector accepted the coating report and the after-galvanizing Charpy results at the first review.

Contact now