Hot-Dip Galvanized Round Bar (Zinc 30–700 g/m²)
Hot-dip galvanized round bar with a zinc coating from 30 to 700 g/m² total on both surfaces, in diameters from 6 mm to 60 mm, in 6 m, 9 m and 12 m lengths or in coils. The coating is metallurgically bonded to a Q235B or S235JR-equivalent base bar, so it protects the steel by sacrificial action and keeps working at cut ends, drilled holes and welded joints.
Product Overview
Hot-dip galvanized round bar starts as an ordinary hot-rolled round bar, which is cleaned and then immersed in a molten zinc bath so that a zinc-iron alloy layer forms across the whole surface, including the cut ends and any drilled holes. The coating is not a paint film sitting on top of the steel: it is metallurgically bonded and it protects the steel by sacrificing itself, which is why galvanized bar keeps its integrity for decades outdoors where an untreated black bar would have rusted at the first scratch.
The important number is the coating weight, not the fact that the bar is galvanized at all. We supply from 30 g/m² for dry indoor duty up to 700 g/m² for severe marine and industrial atmospheres, quoted as the total on both surfaces, with a working guide of about 7 micrometres of coating thickness per 100 g/m². For coastal structures, earthing systems in humid climates and any product that will be exposed, handled and scratched on site, we normally recommend a heavier coating rather than a nominal one, and a heavy-coating line of about 70 micrometres is held for earthing and similar duty.
The base bar is Q235B to GB/T 700, the closest Chinese equivalent to S235JR, and bar can also be supplied over quality-carbon, alloy or stainless base grades where the application needs strength more than the coating. Standard delivery is 6 m, 9 m or 12 m straight lengths, with coils for the small sizes, and bar can be cut, drilled or threaded before galvanizing so that the finished part arrives fully coated rather than with bare steel at the machined areas.
Specifications & Size Range
Finished, coated sizes held in stock, with lengths, coating weights and typical uses. The sizes listed are the finished diameters as supplied; diameters from 28 mm upward and coatings outside the standard bands are produced to order. Cut, drilled and threaded bar can be galvanized after processing so that the part arrives fully coated.
| Size group | Finished diameter (mm) | Standard length | Coating | Typical use |
|---|---|---|---|---|
| Small coated sizes | 6.5 / 7.8 / 8.8 / 9.2 / 9.5 / 9.8 | 6 m, or coil for the smallest sizes | 30–200 g/m² | Fencing, trellis, mesh frames, light earthing |
| Medium coated sizes | 10.5 / 11.2 / 11.5 / 11.8 / 13.5 / 13.8 | 6 m / 9 m | 60–275 g/m² | Earthing rods, fence posts, greenhouse frames, handrails |
| Larger coated sizes | 15.5 / 15.8 / 18 / 20 / 25 | 6 m / 9 m | 100–500 g/m² | Earthing and lightning protection, coastal structures, brackets |
| Heavy-coating line | 7.8 – 25 as above | 6 m / 9 m | about 70 micrometres | Earthing duty where a heavy coating is specified |
| Large diameter (to order) | 28 / 32 / 36 / 40 / 50 / 60 | 6 m / 9 m / 12 m, cut to order | to specification | Heavy earthing, marine structures, exposed frames and rods |
Tolerances
Coating to GB/T 13912 / ISO 1461 / ASTM A123 / JIS H8641, quoted in g/m² total on both surfaces, with a working guide of about 7 micrometres of coating thickness per 100 g/m². Coating mass is checked on a sample basis per lot and a coating test report travels with the shipment. Dimensions and straightness of the base bar follow GB/T 702, and the diameter quoted on the certificate refers to the coated size as supplied.
Steel Grades & International Equivalents
All grades below are supplied with a mill test certificate. The right-hand column shows the material type and the Chinese standard the grade is produced to; the middle columns give the nearest recognised equivalent in other national standards. Exact equivalence for a specific project should be confirmed on the enquiry.
| GB (China) | ASTM / AISI (US) | EN (Europe) | JIS (Japan) | DIN (Germany) | Type / Standard |
|---|---|---|---|---|---|
| Q235B + hot-dip galvanized | A123 / A153 (ASTM) | EN ISO 1461 | JIS H8641 | DIN 50976 | Hot-dip galvanized structural steel (GB/T 13912) |
| Q235B | A36 / A283 Gr.C | S235JR (EN 10025-2) | SS400 (JIS G3101) | St37-2 | Carbon structural steel (GB/T 700) |
Grade Notes
- Q235B + hot-dip galvanized — Zinc coating of 30–700 g/m² gives 5–30+ years of atmospheric corrosion protection depending on thickness and environment.
- Q235B — The workhorse structural grade in China. Fully weldable, excellent cost-performance, the closest Chinese equivalent to ASTM A36 / EN S235JR.
Chemical Composition (%, ladle analysis)
Typical specification limits. Actual heat values are reported on the mill test certificate supplied with every shipment.
| Grade | C | Si | Mn | P max | S max | Other elements |
|---|---|---|---|---|---|---|
| Q235B | ≤0.20 | ≤0.35 | ≤1.40 | ≤0.045 | ≤0.045 | — |
Mechanical Properties
Minimum values at room temperature unless stated. ReL = yield strength; Rp0.2 = 0.2% proof stress; Rm = tensile strength; A = elongation after fracture.
| Grade | Yield (ReL) | Proof (Rp0.2) | Tensile (Rm) | Elongation A | Impact / others | |
|---|---|---|---|---|---|---|
| Q235B + hot-dip galvanized | — | — | — | — | — | Coating 30–700 g/m² (both sides), made to order Adhesion per GB/T 13912 bend test |
| Q235B | ≥235 MPa | — | 370–500 MPa | ≥26% | +20 °C, ≥27 J | — |
Standards & Documents
- GB/T 13912 — hot-dip galvanized coatings on fabricated iron and steel articles
- ISO 1461 / EN ISO 1461 — hot-dip galvanized coatings (international equivalent)
- ASTM A123 / A153 — zinc (hot-dip galvanized) coatings on iron and steel products
- JIS H8641 — hot-dip zinc coatings (Japanese equivalent)
- GB/T 702 — hot-rolled round and square steel bars: dimensions and tolerance of the base bar
- Zinc bath to EN 1179 (Zn at 99.995 per cent or above); coating mass test report and EN 10204 3.1 mill certificate with each lot
Typical Applications
| Industry / Application | Typical use |
|---|---|
| Earthing & lightning protection | Earth rods, earth tapes and down conductors for substations, telecom sites, solar farms and buildings, where the coating has to survive being driven into the ground and still conduct after years of burial. |
| Fencing posts & gates | Field fencing, security fences, gate frames and rails, where the bar is left exposed and no painting or repainting programme is wanted. |
| Coastal & marine engineering | Jetty furniture, sea-wall reinforcement, handrails and frames exposed to salt spray, using a heavier coating selected against the corrosion class of the site. |
| Solar, greenhouse & agricultural frames | Ground-mount and rooftop support bases, greenhouse frames, orchard trellis and livestock structures where a long maintenance-free life is expected. |
| Road, rail & public infrastructure | Guard-rail support rods, sign frames, barrier components, drainage gratings and street furniture. |
| Industrial platforms & handrails | Walkway frames, stair handrails, pipe supports, equipment guards and general secondary steelwork in wet or outdoor plant areas. |
| Machinery & fabricated parts | Rods, pins, brackets and general machined parts used outdoors or in humid plant, where a coated stock bar is preferred to coating after machining. |
Common Problems Buyers Face — and How We Prevent Them
These are the issues that most often cause claims on steel imports. Each one is controlled in our process before shipment.
White rust appearing on the coating during transit
Why it happens: Zinc reacts with moisture when air cannot circulate between bundled bars, producing wet-storage stain. It is a surface product rather than a loss of coating, but it looks like a defect at receiving inspection.
Our control: Bar is bundled with spacers so air can pass, shipped dry, and VCI paper is added where the route is long or crosses humid zones. Where appearance matters, a passivation (chromate) treatment can be applied to suppress wet-storage stain.
Coating mass measured below the specification
Why it happens: Short dipping time, a low bath temperature or handling damage can leave thin or bare patches, and a single spot reading at receiving inspection can fail the lot.
Our control: Coating mass is checked on a sample basis per lot and a coating test report travels with the shipment, so the material is measured against the standard before it is loaded rather than argued about at the port. If your specification sets a minimum individual reading as well as an average, state that on the enquiry.
Bare steel exposed where the bar was cut or threaded
Why it happens: Cutting, drilling and threading after galvanizing remove the zinc locally and leave the steel unprotected at exactly the point where water collects.
Our control: Cut, drill and thread before galvanizing so that the finished part arrives fully coated, and we will quote the processed and then galvanized item. Where site cutting is unavoidable, a zinc-rich repair coating should be applied to the cut area and we can supply the correct touch-up material with the order.
Distortion in small diameter bar after galvanizing
Why it happens: The thermal cycle of the galvanizing bath releases rolling stresses, so light bar in long lengths can bow, which shows up when a fence line will not run straight.
Our control: Long slender bar is jigged during dipping and straightness is checked after galvanizing. Where straightness is critical, tell us at the enquiry stage: a heavier base bar or a shorter delivered length is often the simplest answer.
Black bar delivered in place of galvanized bar
Why it happens: The two can look similar inside a wrapping, and the difference only becomes clear when the bar starts to rust a few weeks after installation.
Our control: Every bundle is tagged by size, heat number and coating weight, the coating test report is matched to the tag, and the packing list states the coating mass for each item so that a receiving check can be completed without unwrapping the whole bundle.
Our Supply & Manufacturing Advantages
- Coating made to your specification — 30 to 700 g/m² quoted on the enquiry and matched to the atmosphere the product will actually be exposed to, rather than a nominal coating that fails in a coastal environment.
- Heavy-coating line for earthing duty — A heavy coating of about 70 micrometres is held for earthing and similar exposed duty, which is where a standard coating is often marginal.
- Processing before galvanizing — Cutting, drilling and threading ahead of dipping means the finished part has no bare steel at machined areas and no site rework.
- Base grades to suit the load — Q235B and S235JR-equivalent base bar as standard, with quality-carbon, alloy or stainless base grades available on request for parts where the coating alone does not justify the strength.
- Documented coating — A coating mass test report plus an EN 10204 3.1 mill certificate for the base bar with every lot, with SGS or BV inspection on request.
- Export packaging included — Bundled and strapped for container loading with spacers and edge protection so that the coating survives handling and arrives without wet-storage stain.
Packaging, Delivery & Payment
- Packing: loose in bulk vessel, or bundled and containerised to your requirement. Galvanized and coated products get VCI paper, waterproof wrapping and edge protection. See our export packaging methods.
- Availability: both stock and custom production. Tell us the specification and we will confirm the route.
- MOQ: no strict minimum — one ton can ship.
- Lead time: stock dispatched to port within 3 days; orders needing export packaging about 1 week; custom production quoted per product.
- Payment: stock — 10% deposit, balance before shipment; custom production — 50% deposit, balance before shipment.
- Documents: EN 10204 3.1 mill test certificate with every shipment; third-party inspection (SGS / BV) on request.
Frequently Asked Questions
How thick a zinc coating should I specify for a round bar?
As a practical guide: 30 to 100 g/m² is enough for dry indoor service; 180 to 275 g/m² suits general outdoor inland exposure and is the most common export specification; 350 to 500 g/m² is used for coastal and industrial atmospheres; and 600 to 700 g/m², or the heavy-coating line of about 70 micrometres, is used for severe marine or buried duty such as earthing rods. Coating mass is quoted as the total on both surfaces. Tell us where the bar will be installed and we will nominate a coating weight.
What is the difference between galvanized round bar and black round bar?
Black round bar is hot-rolled with only the mill scale on the surface and no corrosion protection, so it must be painted or otherwise treated if it will be exposed to weather. Galvanized round bar carries a metallurgically bonded zinc coating that protects the steel by sacrificial action, including at cut ends and drilled holes, and typically gives decades of maintenance-free service outdoors. The galvanized product costs more per ton but removes the cost of painting, inspection and repainting over the life of the structure.
What coating is used on earthing rods for a coastal site?
For a coastal or high-humidity site we would normally recommend the heavy-coating line at about 70 micrometres, or a coating at the top of the 500 to 700 g/m² band, because an earthing rod is driven into the ground and handled with machinery, so the coating has to tolerate abrasion as well as soil chemistry. Tell us the soil condition, the burial depth and the design life and we will nominate a coating weight and confirm it on the order.
Is your galvanized round bar compliant with ASTM A123?
Yes. The coating is produced and tested to meet the requirements of ASTM A123 as well as GB/T 13912 and ISO 1461. If your project references ASTM A123 explicitly, say so on the enquiry and the coating inspection will be carried out against that standard, with the test report issued accordingly so that the material passes a receiving inspection that quotes the same clause.
Can you cut, drill or thread the bar before galvanizing?
Yes, and we recommend it. Processing before dipping gives a finished part that is fully coated, including the cut ends and the inside of drilled holes, which is exactly where corrosion starts on an outdoor installation. Send the drawing or the cut list and we will quote the processed and then galvanized item rather than plain bar, so that no site rework or zinc-rich touch-up paint is needed.
What is your minimum order quantity and lead time?
There is no strict minimum order quantity and a trial shipment of one ton is possible. Stock sizes in the standard coating bands reach the port within about 3 days; bar that has to be cut, drilled or threaded before galvanizing, or produced with a heavy coating, takes about one week. Where the coating weight is set by a project specification, it is confirmed on the order acknowledgement.
What documents come with a galvanized round bar shipment?
A coating mass test report for each lot plus an EN 10204 3.1 mill certificate for the base bar showing heat number, chemical composition and mechanical properties, together with the commercial invoice, packing list and certificate of origin. SGS or BV inspection, including coating thickness measurement, can be arranged before loading on request.
How is galvanized round bar packed to protect the coating?
Bundles are strapped with spacers between bars so that air can circulate and wet-storage stain does not form, shipped dry with desiccant where the route or season makes condensation likely, and fitted with edge protection so the coating is not scuffed during handling. The packing list records the coating weight for each bundle so the material can be checked against the specification on arrival.
Who supplies hot-dip galvanized round bar from China?
We supply hot-dip galvanized round bar in finished diameters from 6.5 mm to 25 mm from stock, with diameters to 60 mm produced to order, in coatings from 30 to 700 g/m² and in a heavy-coating line of about 70 micrometres for earthing duty. Bar is supplied to GB/T 13912, ISO 1461 and ASTM A123 with a coating test report and a mill certificate, and can be cut, drilled or threaded before galvanizing. Send the sizes, coating weights and tonnage and we will confirm availability and a delivery schedule.
Request a Quotation Export Packaging
Live Stock & Indicative Price
The table below lists live stock at the time of publication, with indicative EXW China reference prices in USD per tonne (converted at 6.70 CNY/USD). Steel prices move with the mill market every week — send us your size, quantity and destination and we will confirm availability and issue a firm FOB or CIF quotation.
| Product | Size / Model | Grade | Price (USD/t, EXW) | Stock (t) |
|---|---|---|---|---|
| Galvanized Round Bar (in-line) | Ø6.5 mm | Q235B | $584 | — |
| Galvanized Round Bar (in-line) | Ø7.8 mm | Q235B | $539 | 5 |
| Galvanized Round Bar (in-line) | Ø8.8 mm | Q235B | $528 | 3 |
| Galvanized Round Bar (in-line) | Ø9.2 mm | Q235B | $528 | 3 |
| Galvanized Round Bar (in-line) | Ø9.5 mm | Q235B | $528 | 6 |
| Galvanized Round Bar (in-line) | Ø9.8 mm | Q235B | $528 | 9 |
| Galvanized Round Bar (in-line) | Ø10.5 mm | Q235B | $528 | 1 |
| Galvanized Round Bar (in-line) | Ø10.8 mm | Q235B | $528 | 3 |
| Galvanized Round Bar (in-line) | Ø11.2 mm | Q235B | $528 | 3 |
| Galvanized Round Bar (in-line) | Ø11.5 mm | Q235B | $528 | 8 |
| Galvanized Round Bar (in-line) | Ø11.8 mm | Q235B | $528 | 11 |
| Galvanized Round Bar (in-line) | Ø13.5 mm | Q235B | $536 | 4 |
| Galvanized Round Bar (in-line) | Ø13.8 mm | Q235B | $536 | 7 |
| Galvanized Round Bar (in-line) | Ø15.5 mm | Q235B | $536 | 3 |
| Galvanized Round Bar (in-line) | Ø15.8 mm | Q235B | $536 | 5 |
| Galvanized Round Bar (in-line) | Ø18 mm | Q235B | $537 | 1 |
| Galvanized Round Bar (in-line) | Ø20 mm | Q235B | $537 | 5 |
| Galvanized Round Bar (classic) | Ø25 mm | Q235B | $594 | 4 |
Showing 18 of 18 listed sizes. Price range USD 528–594 per tonne (EXW China). MOQ from 1 tonne; stock dispatched to port within 3 days. Mill test certificate (EN 10204 3.1) and third-party inspection available on request.