The specification an overseas buyer names when they will not accept an IS grade. The Table 1 coating grades, the IS 4759 comparison, and what we will and will not claim.
ASTM A123 sets minimum average coating thicknesses for hot-dip galvanized iron and steel products, expressed as coating grades in microns. Unlike the Indian standard it varies the requirement by material category as well as by steel thickness — structural shapes, plate, strip and bar, pipe and tubing, wire and reinforcing bar each have their own column.
For the structural work most buyers send us, the governing figure is Grade 100 — 100 microns — for steel over 1/4 inch (about 6.4 mm). That is meaningfully heavier than the IS 4759 equivalent of roughly 85 microns, and it is the single most common reason an export specification and a domestic one produce different answers on the same drawing.
By material category and steel thickness. Grades are stated in microns.
| Material category | Steel thickness | Coating grade |
|---|---|---|
| Structural shapes | Under 1/16 in | 45 µm (1.8 mil) |
| Structural shapes | 1/16 to 1/8 in | 65 µm (2.6 mil) |
| Structural shapes | 1/8 to 1/4 in | 75 µm (3.0 mil) |
| Structural shapes | Over 1/4 in | 100 µm (3.9 mil) |
| Plate, strip and bar | Under 1/16 in | 45 µm (1.8 mil) |
| Plate, strip and bar | 1/16 to 1/8 in | 65 µm (2.6 mil) |
| Plate, strip and bar | 1/8 to 5/8 in | 75 µm (3.0 mil) |
| Plate, strip and bar | Over 5/8 in | 100 µm (3.9 mil) |
| Pipe and tubing | All | 45–75 µm (1.8–3.0 mil) |
| Wire | All | 35–80 µm (1.4–3.1 mil) |
| Reinforcing bar | Over 1/4 in | 100 µm (3.9 mil) |
Grades are minimum average thicknesses over the specimen. ASTM A123 also requires the finish to be continuous, smooth and uniform, free of uncoated areas, blisters, flux deposits and gross dross inclusions, and the coating to adhere for the service life of the article. Fasteners and small hardware fall under ASTM A153, not A123.
Same intent, different arithmetic. The gap is real and it is worth pricing.
| IS 4759 | ASTM A123 | |
|---|---|---|
| Expressed as | Coating mass, g/m² | Coating thickness, microns |
| Heavy structural section | 610 g/m² ≈ 85 µm | Grade 100 — 100 µm |
| Varies by | Steel thickness | Material category and steel thickness |
| Uniformity check | Copper sulphate dip, IS 2633 | Visual finish and adherence criteria |
| Referee method | Stripping, IS 6745 | Magnetic thickness measurement, weighing methods |
We describe these as equivalent practice. Indo East does not hold ASTM A123 as a certification, and no honest Indian galvanizer does — A123 is a product specification a coating is supplied against, not a certificate a plant is issued. What we do is galvanize to the grade you name and certify the readings.
Answered from our own line, not from the standard's cover page.
For structural shapes over 1/4 inch — about 6.4 mm — Table 1 calls for Grade 100, meaning a minimum average of 100 microns. Thinner material steps down through 75, 65 and 45 microns.
They do the same job in different units. IS 4759 states a coating mass in g/m²; ASTM A123 states a thickness in microns and varies it by material category as well. For heavy structural sections the IS requirement of 610 g/m² works out at roughly 85 microns against A123's Grade 100, so an A123 order carries a genuinely heavier coating.
No, and nor is any other galvanizer — ASTM A123 is a specification that a coating is supplied against, not a certification a plant holds. What we do is galvanize to the grade you specify and issue the coating thickness readings to prove it, open to third-party witness.
ASTM A153, not A123. Fasteners are centrifuged after dipping and carry their own coating requirements. We supply foundation and anchor bolts in IS 1367 property classes 4.6, 5.6 and 8.8.
Yes. Indo East holds Import Export Code 0211004090 and RCMC/EEPCINDIA/07882/2026-2027 with EEPC India as a Merchant-cum-Manufacturer Exporter. The works is 22 km from Kolkata Port with NH-6 access. Our direct export record is one consignment — fabricated structural steel to the Maldives in January 2018 under our own IEC — and we state that plainly rather than implying more.
The kettle is 7.0 m × 1.2 m × 1.6 m at 450–460 °C, with double-end dipping for longer members where the geometry allows. Maximum single-piece fabrication weight is 5 tonnes.
Tell us the standard, the coating requirement and the component, and we will confirm in writing what we can hold and how we will certify it. Galvanizing is on our own floor, so the answer comes from us and not from a sub-contractor.
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