Black pipe (no coating) is the cheapest and fine for dry indoor structure and painted work; pre-galvanized pipe costs ~8–15% more and suits fences, greenhouses and outdoor frames; hot-dip galvanized after fabrication costs ~25–40% more but protects inside and out for 20+ years — the choice for water lines, coastal fencing and ground-contact posts.
Both pipes start as the same welded ERW tube — Q195/Q235B strip rolled and seam-welded. What changes is the armor: black pipe is bare steel (often oiled), galvanized pipe carries a zinc layer that sacrifices itself to protect the steel. Choosing wrong costs either money up front or rust down the line. Here's the decision map.
The Three Coating Options
| Option | Price vs Black | Protection | Watch Out |
|---|---|---|---|
| Black (bare, oiled) | baseline | None — must be painted for any outdoor use | Rusts quickly in humidity if unpainted |
| Pre-galvanized (zinc on strip before welding) | +8–15% | Good outside-in; the weld seam zone is bare or lightly recoated | Seam line is the first rust spot |
| Hot-dip galvanized after fabrication | +25–40% | Inside and outside, edges and seams — 20+ years outdoors | Slightly heavier; dimensional growth minimal |
Application Table: What to Order Where
| Application | Order | Why |
|---|---|---|
| Fence posts & rails | Pre-galv; hot-dip if coastal/ground contact | Weather exposure every day; ground posts rot first |
| Greenhouse frames | Pre-galv or hot-dip | Constant humidity inside; condensation attacks bare steel |
| Scaffolding | Hot-dip galvanized | Handled hard, stored outdoors, rental life cycles |
| Indoor structural frames, furniture tube | Black + paint or powder coat | Dry service; paint is the finish anyway |
| Water supply lines | Hot-dip galvanized (or PPR/SS alternative) | Constant water contact, inside and out |
| Signage, street furniture | Hot-dip galvanized + powder coat | Public exposure, appearance matters |
| Conduit & cable protection | Pre-galv | Light duty, dry locations |
Sizes We Supply
- Round pipe: DN15–DN200 (½"–8"), wall 1.8–8.0 mm, in black, pre-galvanized and hot-dip galvanized.
- Square/rectangular tube: 20×20 – 200×200 mm (rect up to 100×400), wall 1.2–11.8 mm — full size table →.
- Grades: Q195/Q215 for light duty, Q235B/S235JR structural, S355JR high-strength.
- Ends: plain, threaded + coupling, grooved; lengths 6 m standard, cut-to-size available.
Cost Math That Decides It
Example: a 500 m fence run of DN40 pipe. Black at $640/t plus paint labor often ends more expensive over 5 years than pre-galvanized at $700/t with zero maintenance — and hot-dip at $830/t wins outright near the coast. Total cost of ownership, not the sticker price, is the deciding metric. Current indicative pipe prices →
Product page: steel pipe range →
Tell us the application — we quote the right coating
Pipe list (size × wall × coating) to [email protected] or WhatsApp +86 191 5745 8011 — black, pre-galv and hot-dip priced side by side in one quotation. MOQ 5 t.
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