Guides
MS vs GI: where each one belongs
MS is bare rolled steel and GI is that same steel run through a hot-dip zinc bath afterward, a coating IS 4759:1996 and IS 277:2018 both set minimum figures for. Indoors, painted and kept dry, MS is the plainer buy; outdoors, damp or against the ground, GI is the one built to take it.
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Jay Shree Infra stocks Solar and HMB sections in both finishes at the Saharsa godown, MS black and galvanised, along with GI pipe and GC sheet for roofing. Not every size is in every finish on a given day. The choice between the two gets made once, before the frame or the roof goes up, because the zinc on a GI piece cannot be added afterward the way a coat of paint can.
Below is what galvanising actually is under the two standards that govern it here, where each finish earns its keep in a Saharsa shed or a gate, and what the choice actually changes on the invoice. Full size lists sit on their own pages: angle, MS pipe and GP sheet each carry the sizes of the line split here.
The two standards
How much zinc a coat has to carry, by article and by class
Minimum zinc a hot-dip coat has to carry, by article and by class, as IS 4759 sets it for fabricated steel and IS 277 sets it for sheet.
Scroll the table sideways to see every column
| What it covers | Standard | Coating class | Minimum zinc massgrams per square metre, both sides |
|---|---|---|---|
| Fabricated structural steel, 5 mm thick and over, the class Solar and HMB angle and flat sections are dipped under once cut to length | IS 4759:1996 | Heaviest class this standard sets for fabricated steel | 610 |
| Fabricated structural steel, under 5 mm to 2 mm thick | IS 4759:1996 | Middle class | 460 |
| Fabricated steel under 2 mm to 1.2 mm, and threaded hardware 10 mm dia and over | IS 4759:1996 | Lightest class this standard sets before its threaded-work rows begin | 340 |
| GC roofing sheet, the class IS 277 itself recommends for a roof | IS 277:2018 | 275 | 275 |
| GP and GC sheet, the heaviest class this standard lists | IS 277:2018 | 600 | 600 |
| GP sheet, the lightest class this standard lists before non-critical, non-roofing use begins | IS 277:2018 | 120 | 120 |
The three IS 4759 rows are Table 1's own thickness bands for fabricated structural steel, hardware and bars, the class Solar and HMB sections are dipped under once they are cut to length. The three IS 277 rows are three of the nine classes Table 3 lists for sheet, from the one the standard itself recommends for a roof to the heaviest and lightest it names; a sheet's class is agreed between the buyer and the mill at the time of order, not fixed by the sheet's own thickness the way IS 4759 fixes it to a structural piece.
The two standards do not share one scale because they are not galvanising the same kind of thing. A structural piece under IS 4759 is dipped whole after it is cut and welded, so its own thickness decides the class: a thicker angle or flat takes the heaviest coat this standard sets, a thinner bracket takes less. A coil under IS 277 is galvanised before it is ever cut or rolled to shape, so its class is a choice made with the mill, not a rule tied to the gauge.
275 grams a square metre is not the middle of IS 277's own range, it is the figure the standard itself names as the recommended minimum for a roof. A GC sheet ordered lighter than that is ordered for something other than a roof, and the standard says so in its own note under the table.
The coating itself
What a hot-dip zinc coat actually is
Galvanising is not paint and it is not a grade of steel. IS 4759 defines it as zinc applied by dipping cast, rolled, pressed or forged steel into a bath that has to run at least 98.5 percent zinc by mass, and the same standard lets a buyer ask for chromating or phosphating afterward where wet storage staining or later painting is a concern. The steel underneath carries no separate specification for having been dipped; a GI angle and an MS angle off the same mill can start as the same steel.
The coat itself is what changes, and it runs as one continuous layer over the whole surface, corners and welds included where the piece went into the bath after fabrication. That is also its one real limit: cut a galvanised piece on site, drill it, or weld through it, and the bare steel left behind at that spot is no longer inside either standard's own figure.
Kahan kaunsa lagta hai
MS indoors and painted, GI outdoors and against damp
MS earns its place wherever the steel is going to be painted, primed or kept dry indoors: a shed's internal bracing, a gate frame that gets a coat of paint every season anyway, fabrication that is going to be welded heavily after the size is cut. Paint is cheaper to renew than a zinc bath is to redo, and MS takes weld and grind marks without the coating question a GI piece raises at the same joint.
GI earns its place wherever water, humidity or the ground itself is going to sit against the steel for years without anyone repainting it: a rolling shutter frame facing the road, a shed's roofing sheet and its purlins, a water line, a gate standing open through the Kosi belt's own monsoon. The zinc is the whole of the protection there, put on once at the bath rather than renewed by hand.
Cost follows the same logic without needing a figure to say it. A heavier class means more zinc bought and more time in the bath, so GI generally costs more than the same MS section at the same size, and the gap widens with the coating class a job actually needs. How much more, for the size and class in front of you, is what the call settles; the standard fixes the coating, not the invoice.
At this counter
Which lines we split into both finishes
Solar and HMB carry both finishes on the same structural sections: angle, flat, square and round in MS black under HMB iGrill, and in galvanised under HMB Grill Guard, with Solar's own range doing the same as Solar Structure and Solar GI. Ask for the finish by name when you order; a black angle and a galvanised one of the same size are two different lines on the rack, not two ends of one line.
Pipe splits the same way, MS pipe and GI pipe both governed by IS 1239, and sheet splits into plain HR and CR steel against GP and GC sheet, which already carry the zinc under IS 277. Not every size is in every finish on a given day; call and we confirm what is standing before a load is cut.
Where IS 277 stops and the order begins
Where the coating class stops answering the question
IS 4759 and IS 277 fix the minimum zinc a coat has to carry, and they say nothing about which finish suits a given job; that judgement sits with whoever is speccing the work, not with either standard. A structural drawing or a tender that names a coating class settles it outright, and that class is what we order against.
Where nothing is specified, the honest answer is still a call rather than a guess: tell us where the piece is going, indoors or out, painted or bare, and we point you at the finish that has actually held up here.
Sources
IS 4759 and IS 277, side by side
IS 4759 for fabricated structural steel and hardware, and IS 277 for sheet, the two documents every figure above comes from.
- IS 4759:1996, hot-dip zinc coatings on structural steel and other allied productsBureau of Indian Standards
- IS 277:2018, galvanized steel strips and sheets, plain and corrugated, product manual with the classification scopeBureau of Indian Standards
- IS 1239 (Part 1), the standard MS pipe and GI pipe are both made to, in the amended notificationBureau of Indian Standards
Questions
MS aur GI ke sawal
MS aur GI me kya asli farak hai?
The steel underneath is usually the same, the coating is not. GI is MS run through a hot-dip zinc bath afterward, a coating IS 4759:1996 and IS 277:2018 both set a minimum mass for, and that zinc layer is the whole of the difference between the two.
Shed ke andar ka kaam MS me kar sakte hain kya?
Yes, and it is usually the cheaper choice there. A frame that gets painted and stays under a shed, dry and out of the weather, does fine in MS; the coating question only becomes worth paying for once the piece is going to stand outside, against damp or the ground, for years without anyone repainting it.
GI, MS se mehenga kyu hota hai?
More zinc and more time in the bath go into it. A heavier coating class needs more of both, so GI generally costs more than the same MS section at the same size, and the gap widens with the class a job needs. The figure for your size is on the call.
Galvanised piece ko site par kaat ya weld kar sakte hain?
Yes, but the zinc at that cut or weld is gone right there, and that edge is bare steel until it is repainted or treated by hand. Plan the cuts before the piece leaves the godown where that is possible, and tell us on the order if heavy site fabrication is coming.
MS pipe aur GI pipe dono IS 1239 me aate hain kya?
Yes, both fall under IS 1239 for the tube itself; GI carries the hot-dip zinc coating on top of it, MS does not. Wall thickness class, light, medium or heavy, is a separate choice from the finish, so say both when you order.
Before you order
Black or galvanised, decided by the job
Is the piece going indoors and painted, or outdoors and bare?
That single fact settles MS or GI faster than anything else here; paint renews cheaply, a zinc coat does not.
Does the drawing or tender name a coating class?
IS 4759 and IS 277 both set classes in grams per square metre; naming one settles the order outright and we quote against it directly.
Will the piece be cut, drilled or welded after it arrives?
Every cut or weld on a GI piece exposes bare steel at that point, so say if heavy site fabrication is planned before we settle the finish.
Which sections and sizes, in MS or GI?
Solar and HMB carry both finishes on angle, flat, square and round; say the finish by name, since a black and a galvanised piece of the same size are two different lines.
Sheet or section, and is it going on a roof?
IS 277 itself recommends a 275 gram class for roofing; a lighter class is ordered for something other than a roof, and we confirm the class on the call.
Contact
Say indoors or outdoors, and the finish follows
MS and GI are not two grades of one steel, they are the same steel with one choice made about the coating, and that choice is cheaper to make once than to redo later. Tell us the section, the size and whether it is going indoors or out, painted or bare, and we quote the finish that has actually held up here. Ring +91 6202 967 218 and the size, the finish and today's rate come back together.
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