What is Galvanized square tube?
Galvanized square tube comes in two very different products that share a name. The first — ours — is pre-galvanized: hot-dip galvanized strip (DX51D+Z275 to EN 10346, about 20 µm of zinc per side) is slit, roll-formed and high-frequency welded into a square tube; the weld seam, which loses its zinc in the heat, is metallised or zinc-sprayed in-line. The result is a bright, straight, spangle-free tube with the zinc everywhere except the cut ends, made at mill speed and priced only about 100 USD/t above black tube. The second is post-galvanized: a black S235JRH tube cut and fabricated, then dipped in a zinc bath to EN ISO 1461, which coats inside, outside and ends with 55–85 µm — two to three times the life, but with the cost, lead time and slight distortion of the dip. Pre-galvanized tube is right for fences, gates, greenhouses, racks, HVAC frames and light outdoor work with a 10–15 year horizon; post-galvanized for structures, guardrails and marine or ground-contact use. Our Dilovası mill rolls the pre-galvanized range from 20×20×1.35 to 100×100×3 and arranges hot-dip galvanizing for the rest.
Galvanized square tube sizes and weight per metre
Pre-galvanized sizes from our mill list — square and rectangular together; kg/m includes the zinc.
| Size (mm) | Wall (mm) | kg/m | kg per 6 m bar |
|---|---|---|---|
| 20 × 20 | 1.35 | 0.83 | 4.96 |
| 20 × 20 | 1.8 | 1.07 | 6.44 |
| 20 × 20 | 2.5 | 1.47 | 8.83 |
| 20 × 30 | 1.4 | 1.07 | 6.4 |
| 20 × 30 | 1.5 | 1.14 | 6.85 |
| 20 × 30 | 1.8 | 1.37 | 8.22 |
| 20 × 30 | 2 | 1.51 | 9.04 |
| 20 × 30 | 2.5 | 1.87 | 11.19 |
| 20 × 40 | 1.2 | 1.11 | 6.67 |
| 20 × 40 | 1.35 | 1.25 | 7.5 |
| 20 × 40 | 1.5 | 1.38 | 8.27 |
| 20 × 40 | 1.8 | 1.64 | 9.83 |
| 20 × 40 | 2 | 1.82 | 10.93 |
| 20 × 40 | 2.5 | 2.26 | 13.54 |
| 25 × 25 | 1.4 | 1.07 | 6.4 |
| 25 × 40 | 1.4 | 1.4 | 8.37 |
| 30 × 30 | 1.2 | 1.11 | 6.67 |
| 30 × 30 | 1.35 | 1.24 | 7.44 |
| 30 × 30 | 1.5 | 1.38 | 8.27 |
| 30 × 30 | 1.8 | 1.64 | 9.83 |
| 30 × 30 | 2 | 1.82 | 10.93 |
| 30 × 30 | 2.5 | 2.26 | 13.54 |
| 30 × 40 | 1.2 | 1.3 | 7.8 |
| 30 × 40 | 1.35 | 1.45 | 8.71 |
| 30 × 40 | 1.5 | 1.61 | 9.68 |
| 30 × 40 | 1.8 | 1.92 | 11.53 |
| 30 × 40 | 2 | 2.14 | 12.81 |
| 30 × 40 | 3 | 3.18 | 19.08 |
| 30 × 50 | 1.2 | 1.49 | 8.93 |
| 30 × 50 | 1.35 | 1.66 | 9.98 |
| 30 × 50 | 1.5 | 1.85 | 11.09 |
| 30 × 50 | 1.8 | 2.21 | 13.23 |
| 30 × 50 | 2 | 2.45 | 14.7 |
| 30 × 50 | 2.5 | 3.04 | 18.25 |
| 30 × 60 | 1.2 | 1.67 | 10 |
| 30 × 60 | 2 | 2.76 | 16.58 |
| 40 × 40 | 1.2 | 1.49 | 8.93 |
| 40 × 40 | 1.35 | 1.66 | 9.98 |
| 40 × 40 | 1.5 | 1.85 | 11.09 |
| 40 × 40 | 1.8 | 2.21 | 13.23 |
| 40 × 40 | 2 | 2.45 | 14.7 |
| 40 × 40 | 2.5 | 3.04 | 18.25 |
| 40 × 40 | 3 | 3.63 | 21.76 |
| 40 × 50 | 2 | 2.76 | 16.58 |
| 40 × 50 | 2.5 | 3.44 | 20.61 |
| 40 × 50 | 3 | 4.07 | 24.44 |
| 40 × 60 | 1.2 | 1.87 | 11.19 |
| 40 × 60 | 1.35 | 2.09 | 12.53 |
| 40 × 60 | 1.5 | 2.32 | 13.92 |
| 40 × 60 | 1.8 | 2.77 | 16.62 |
| 40 × 60 | 2 | 3.08 | 18.46 |
| 40 × 60 | 2.5 | 3.83 | 22.96 |
| 40 × 60 | 3 | 4.57 | 27.41 |
| 40 × 80 | 1.4 | 2.61 | 15.63 |
| 40 × 80 | 1.8 | 3.34 | 20.01 |
| 40 × 80 | 2 | 3.71 | 22.23 |
| 40 × 80 | 2.5 | 4.61 | 27.67 |
| 40 × 80 | 3 | 5.49 | 32.92 |
| 50 × 50 | 1.2 | 1.87 | 11.19 |
| 50 × 50 | 1.35 | 2.09 | 12.53 |
| 50 × 50 | 1.5 | 2.32 | 13.92 |
| 50 × 50 | 1.8 | 2.77 | 16.62 |
| 50 × 50 | 2 | 3.08 | 18.46 |
| 50 × 50 | 2.5 | 3.83 | 22.96 |
| 50 × 50 | 3 | 4.57 | 27.41 |
| 50 × 100 | 2.5 | 5.61 | 33.68 |
| 50 × 100 | 3 | 6.67 | 39.99 |
| 60 × 60 | 1.2 | 2.23 | 13.4 |
| 60 × 60 | 1.35 | 2.51 | 15.07 |
| 60 × 60 | 1.5 | 2.79 | 16.74 |
| 60 × 60 | 1.8 | 3.33 | 20 |
| 60 × 60 | 2 | 3.69 | 22.14 |
| 60 × 60 | 2.5 | 4.61 | 27.67 |
| 60 × 60 | 3 | 5.51 | 33.06 |
| 80 × 80 | 2.5 | 6.01 | 36.03 |
| 80 × 80 | 3 | 7.14 | 42.81 |
| 100 × 100 | 3 | 9.07 | 54.4 |
Roll-formed from DX51D+Z275 strip in our Dilovası tube mill; 6 m lengths.
Grades, standards and tolerances
| Grade / standard | Yield (MPa) | Note |
|---|---|---|
| DX51D+Z275 (pre-galvanized strip) | ≈ 280 (typ.) | the standard — no guaranteed yield, bending grade |
| S250GD / S280GD+Z275 | ≥ 250 / 280 | structural pre-galvanized on request |
| S235JRH + HDG EN ISO 1461 | ≥ 235 | black tube hot-dip galvanized after cutting |
| S355J2H + HDG | ≥ 355 | structural, post-galvanized |
Pre-galvanized tube keeps EN 10219 dimensions; the Z275 coating is about 20 µm per side and the weld seam is zinc-repaired in-line. Post-galvanized tube carries 55–85 µm and needs vent holes.
Pre-galvanized vs hot-dip galvanized tube
| Pre-galvanized (from Z275 strip) | Hot-dip galvanized after fabrication | |
|---|---|---|
| Coating | ≈ 20 µm per side (Z275), weld seam sprayed | 55–85 µm, all surfaces incl. inside and cut ends |
| Life (C3) | 10–15 years | 25–40 years |
| Appearance | bright, smooth, spangle-free | grey, thicker, possible runs |
| Straightness | unchanged (no heat) | may distort; needs straightening |
| Sizes | 20×20–100×100, ≤ 3 mm | any, needs vent holes |
| Price | base | +150–200 USD/t |
| Best for | fences, greenhouses, racks, furniture, HVAC | structures, guardrails, marine, ground contact |
Lengths and stock
Length 6 m (+50/−0); cut lengths ±3 mm. Stock at Dilovası: 20×20, 25×25, 30×30, 40×40, 50×50, 60×60 in 1.35–2 mm; 80×80 and 100×100 in 2–3 mm rolled within a week. Dimensional tolerances per EN 10219-2; coating Z275 per EN 10346 (Z140 on request for painted parts).
Cutting, welding and coating
Saw and laser cutting leave a bare edge — spray with zinc-rich paint or accept it for indoor use. Welding pre-galvanized tube needs fume extraction; the seam is repaired with zinc paint. Powder coating adheres directly after degreasing (order Z140 M for the best paint base). For outdoor structures, guardrails and anything with a design life above 15 years we recommend black tube hot-dip galvanized after fabrication to EN ISO 1461 — priced per ton on top of the black tube.
Where it is used
- Fence, gate and railing frames
- Greenhouse, poultry-house and shade-net frames
- Racking, shelving and display stands
- HVAC and duct support frames
- Solar mounting for small installations
- Playground, sports and sign frames
Galvanized square tube vs black square tube
Black square hollow section costs about 100 USD/t less and is the right choice for anything that will be painted or galvanized after fabrication; pre-galvanized tube saves the coating step for light outdoor frames. For rectangular sizes see galvanized rectangular tube; for the strip behind it, DX51D galvanized steel.
Price
Pre-galvanized tube is priced per ton on the galvanized-tube list — about 100 USD/t above black tube for the zinc and the strip. Hot-dip galvanizing after fabrication is quoted per ton of finished tube. Bands below.
Bands from our weekly export list (September 2026), FOB Istanbul, full-container quantities, excluding freight and certificates. Firm price per project on RFQ within one working day.
Export and packing
Packing for Galvanized square tube: bundles of one size (0.8–2 t), four steel straps, corner boards and a tag carrying size × wall × length, grade, heat and count; coated sections are separated with paper. 6 m bundles fill a 40' HC at 24–25 t; 12 m lengths ship on flat-rack or as breakbulk from Derince. Tariff 7306.61.
| Term | Detail |
|---|---|
| MOQ | 5 t (mixed sizes accepted) |
| Incoterms | FOB Istanbul · CIF / CFR Gulf, Africa · DAP EU, Balkans, Iraq, Caucasus · DAP Aktau |
| Lead time | Stock 20×20–60×60: 2–5 working days; other sizes 5–10 days; HDG +7 days |
| Packing | Bundles 0.8–1.5 t, strapped with paper separators, tagged |
| Container / truck | 40' HC ≈ 24–25 t of 6 m |
| Documents | Invoice, packing list, EN 10204 3.1, CE DoP (EN 10219-1), certificate of origin; SASO / SONCAP / PVoC on request |
| Payment | 30% advance, balance against B/L copy; L/C at sight above 100 t |
Certificates
Every bundle of Galvanized square tube is traceable to the strip heat: an EN 10204 3.1 certificate with chemistry and mechanicals alongside our tube-mill inspection record for dimensions and the weld flattening test. We supply the EN 10219-1 CE declaration as a matter of course; an inspected 3.2 release is quoted separately.
How to order
Send size × wall × length, quantity, coating (pre-galvanized Z275 / Z140, or HDG after cutting), any cutting or drilling, and the use — we advise between pre- and post-galvanized.
Standards
- EN 10219-1/2 — cold-formed hollow sections (dimensions)
- EN 10346 — DX51D+Z275 strip (pre-galvanized)
- EN ISO 1461 — hot-dip galvanizing after fabrication (option)
- EN 10204 3.1
Grades
Grade data sheets (chemistry, mechanicals, equivalents) are on our reference site: DX51D · S235JRH · S250GD
Frequently asked questions
What is galvanized square tube?
Square hollow section rolled from hot-dip galvanized (Z275) strip, so the zinc is applied at the mill before forming — bright, straight and paintable; or black tube hot-dip galvanized after fabrication for heavier protection.
What is the difference between pre-galvanized and hot-dip galvanized tube?
Pre-galvanized carries about 20 µm of zinc from the strip (Z275) and a repaired seam; hot-dip after fabrication carries 55–85 µm on all surfaces including the inside and cut ends, lasts 2–3 times longer and costs 150–200 USD/t more.
What sizes of galvanized square tube do you make?
20×20 to 100×100 mm in 1.35–3 mm walls pre-galvanized; any black size can be hot-dip galvanized after cutting.
Can galvanized square tube be welded?
Yes with fume extraction; the zinc burns off 1–2 mm around the weld and is repaired with zinc-rich paint. For structural welds use black tube and galvanize afterwards.
How long does galvanized square tube last outdoors?
Pre-galvanized Z275: 10–15 years to first rust in a normal urban climate; hot-dip galvanized after fabrication: 25–40 years.