Hot-dip galvanizing and powder coating — arranged for every order
Galvanizing is not done in our plant — it is done 20 km away in a partner plant with a 13 m bath — but it is done on our order, on our truck, with our certificate, and invoiced on our line. Powder coating, alone or over zinc as a duplex system, the same. The customer receives finished, coated steel from one supplier.
Hot-dip galvanizing
To EN ISO 1461 in a 13 000 × 1 800 × 3 000 mm kettle (parts to 12.5 m in one dip, to 20 m by double dipping): degreasing, pickling, fluxing, zinc at 450 °C, quench and passivation; coating thickness per the standard — 55 µm minimum on 1.5–3 mm, 70 µm on 3–6 mm, 85 µm on > 6 mm (local minimum), typically 80–140 µm on structural sections — giving 30–60 years to first maintenance inland. Sections, tube, hollow sections, grating, ladders, fabricated frames, brackets and fasteners; centrifuge galvanizing for small parts; capacity 3 000 t a month.
Design for galvanizing
- Vent and drain holes in every closed section (hollow sections, tube, posts): Ø ≥ 10 mm or 25 % of the section size, diagonally opposite at each end
- Avoid overlapping surfaces and sealed pockets — they burst or stay uncoated; seal-weld or leave 2–3 mm gaps
- Mixed thicknesses in one assembly distort — keep within 1:2.5; long thin members need lifting points
- Thread allowances: M12 and above cut oversize by 0.4 mm or re-tapped after galvanizing
- No paint, grease markers or heavy weld spatter; silicon in steel (0.03–0.13 %) gives thick, dull grey coatings — S355J2 with low Si preferred for appearance
- We check drawings for galvanizing suitability before fabrication
Powder coating and duplex systems
| System | Build | Corrosion class (ISO 12944) | Colour | Use |
|---|---|---|---|---|
| Hot-dip galvanizing only | 70–140 µm Zn | C3–C4, 30–60 yr | grey | structural, fencing, grating |
| Powder coating on blasted steel | zinc-rich primer 60 µm + polyester 80 µm | C3, 10–15 yr | any RAL | indoor frames, furniture, racks |
| Duplex: galvanized + powder | Zn + sweep blast + polyester 80–100 µm | C4–C5, 1.5–2.5 × the sum of both | any RAL | railings, car-park barriers, coastal fencing, architecture |
| Wet paint ISO 12944 | blast Sa 2½ + epoxy 2 × 80 + PU 60 µm | C4–C5 | any RAL | plant steelwork, tanks |
| Shop primer only | blast + 20–25 µm zinc silicate | transport protection | grey / red | steel to be painted on site |
Powder booth 7 000 × 2 000 × 2 200 mm, oven 8 m; parts to 400 kg on the conveyor.
Logistics and documentation
Steel goes from our cutting and fabrication shops to the galvanizer and back on our trucks (2–5 working days in the cycle, 5–8 for duplex), is inspected for thickness (magnetic gauge, five readings per reference area per EN ISO 1461 §6), touched up where the standard allows, and packed with separators to avoid wet-storage stain; the galvanizing certificate (thickness, batch, standard) and the powder-coating batch sheet ship with the material certificates.
Pricing
Galvanizing is charged per ton by part type (structural sections and tube about 350–450 USD/t, grating and small parts more, fasteners per kg), duplex and powder coating per m² of surface (8–15 USD/m² by colour and build), wet paint per m² by system; shown as separate lines on the steel offer. Minimum lot 1 t.
Frequently asked questions
Do you galvanize in-house?
No — at a partner plant 20 km away with a 13 m bath, on our order, transport and certificate; it is one line on our invoice.
What coating thickness does hot-dip galvanizing give?
Per EN ISO 1461: 55 µm minimum on 1.5–3 mm steel, 70 µm on 3–6 mm, 85 µm above 6 mm; typically 80–140 µm on sections — 30–60 years inland.
Can galvanized steel be powder coated?
Yes — the duplex system (sweep blast + polyester powder) gives any RAL colour and 1.5–2.5 times the life of either coating alone; used for railings, barriers and architectural work.
What must I consider when designing for galvanizing?
Vent and drain holes in closed sections, no sealed pockets or overlaps, balanced thicknesses, thread allowances; we check drawings before fabrication.