The four systems aren't tiers of the same coating — they're distinct chemistries with different coating-mass conventions, and each maps more naturally to one of our two product lines.
For industrial steel structures
Galvanized steel (GI)
IS 277:2018 · Coating class Z80, Z120, or Z275
The standard for enclosed and roof-covered applications. For PEB purlins sitting under cladding, Z275 is the common choice — the coating's job is surviving erection handling and interior condensation, not decades of direct weathering, so the mid-range class is usually sufficient.
Hot-dip galvanized structural steel
IS 4759 on IS 2062 base · 460 GSM (>60μ) or 600 GSM (>80μ)
Meaningfully heavier than IS 277's classes, applied by batch-dipping fabricated members rather than coil coating. This is the system for PEB primary steel and post-fabrication components — brackets, base plates.
For solar ground-mount MMS
Zn-Al-Mg alloy coated
IS 18513:2023 · Coating class ZM120 or ZM150
Delivers meaningfully better corrosion resistance than pure zinc at equivalent coating mass, including better cut-edge protection — relevant for MMS members punched and slotted after coating. The strongest technical fit for MMS purlins and rafters on our line; ZM150 plus field touch-up at punched holes is the closest match to a 25-year exposure target.
Aluminium-zinc alloy coated (Galvalume)
IS 15961:2012 · Coating class AZ150, down to 0.7 mm
55% Al content gives strong heat reflectivity and corrosion resistance, and pairs with the YS 550 grade to enable thinner, lighter MMS components — clamps, rails, lighter-duty purlins — than the Zn-Al-Mg system supports at comparable thickness. The better choice where minimizing weight matters more than maximizing edge-cut protection.
Quick reference
| System | Standard | Coating class | Best fit |
|---|---|---|---|
| GI | IS 277:2018 | Z80 / Z120 / Z275 | PEB roof-covered purlins |
| Hot-dip structural | IS 4759 | 460 / 600 GSM | PEB primary steel, MMS foundation posts |
| Zn-Al-Mg | IS 18513:2023 | ZM120 / ZM150 | MMS purlins/rafters, 25-yr target |
| Galvalume | IS 15961:2012 | AZ150 | MMS light components, weight-sensitive parts |
Not sure which coating system fits your site?
Send us the plant location, the design life you are working to and the member schedule. We will tell you which coating system we would put on it and why.
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