Base steel grade isn't an independent choice — it's fixed by which of four coating systems the coil runs through. These are the systems used across our roll-forming lines.
| Coating system | Standard | Grade options | Thickness range |
|---|---|---|---|
| Galvanized steel (GI) | IS 277:2018 | YS 250, YS 350 | 1.6–3.0 mm |
| Hot-dip galvanized structural steel | IS 2062:1992 base / IS 4759 coating | E250, E350 | 1.6–3.0 mm |
| Zn-Al-Mg alloy coated | IS 18513:2023 | IZMC300S, IZMC350S | 1.6–3.0 mm |
| Aluminium-zinc alloy coated (Galvalume) | IS 15961:2012 | YS 350, YS 550 | 0.7–3.0 mm |
Where the two industries diverge
Roof-covered PEB purlins and fully exposed solar tables carry different loads, different exposure, and different service-life targets — which pushes each toward a different pair of systems from the table above.
Industrial steel structures
PEB purlins run almost entirely on IS 277 GI coil (YS 250/YS 350) for standard secondary framing. Where a heavier member is needed — primary rafters, base plates, site-fabricated brackets — the substrate is IS 2062 E250/E350 hot-rolled structural steel, hot-dip galvanized to IS 4759 rather than continuous-coil coated. E350 over E250 buys higher yield strength at the same section depth, which is where tonnage savings show up on longer bays.
Ground-mount solar MMS
IS 18513 Zn-Al-Mg (IZMC300S/350S) and IS 15961 Galvalume (YS 350/550) are both coil-based and roll-forming-friendly, which matters since MMS members are roll-formed then field-punched, not fabricated-then-dipped. The upper grades in each give enough strength headroom to hold thickness down on long-span tables while still meeting a 25-year coating durability target. Galvalume also runs as thin as 0.7 mm — useful for lighter clamp and rail components with no comparable low-gauge option in IS 277 or IS 2062.
Quick reference
| Parameter | PEB / Industrial | Solar Ground-Mount MMS |
|---|---|---|
| Primary system | IS 277 GI, or IS 2062 + IS 4759 for heavy members | IS 18513 Zn-Al-Mg or IS 15961 Galvalume |
| Grade | YS 250/350 (GI), E250/E350 (structural) | IZMC300S/350S, or YS 350/550 |
| Thickness | 1.6–3.0 mm | 1.6–3.0 mm coil, down to 0.7 mm for light parts |
Not sure which grade your design calls for?
Send us the member schedule and the site location. We will confirm the coating system, grade and thickness we would roll it in, along with the material certificate.
Ask about gradesAlso in this series