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
Galvanized square tube is bundled in hexagonal or square packs of 0.8–2 t, strapped at four points with edge protectors, tagged with size, wall, grade, length and bar count; galvanized and painted bundles get paper or foam separators. A 40' HC takes 24–25 t of 6 m bars, a 20' about 20 t; 12 m bars go on flat-racks. HS 7306.61 (square/rectangular welded).
| 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
Documentation for Galvanized square tube: strip mill certificate EN 10204 3.1, our production record (size, wall, straightness, weld test), CE DoP under EN 10219-1; third-party 3.2 certificates on request.
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.