Stainless Steel Grades: 202 vs 304 vs 316

Stainless steel is everywhere in Indian homes and buildings — kitchen sinks, utensils, trolley baskets, balcony and staircase railings, bathroom accessories, door hardware, stone cladding anchors, gates and furniture legs. It is also one of the most misunderstood materials in the trade. The word stainless on a quotation tells a buyer almost nothing, because stainless steel is a family of alloys, and the cheapest members of that family can show rust spots within months in a humid or coastal city while the better grades stay bright for decades.

In India the confusion centres on three grades: 202, 304 and 316. They look identical when new, are all sold as SS, and can be polished to the same finish. They differ in what is inside — chiefly nickel, manganese and molybdenum — and therefore in how they resist corrosion and what they cost. A railing in 202 on a Mumbai sea-front balcony, a kitchen sink in an unknown grade, or bathroom hooks that start to rust behind the towels are all symptoms of the same mistake: choosing on price and appearance instead of on environment.

This article explains what the three grades are made of, why they behave differently, which one belongs where in a home or building, how to verify what has actually been supplied, and what each costs in October 2026. It also corrects a common myth about the magnet test. The guidance is consistent with this site's articles on kitchen trolleys, railings, bathroom fittings and stone cladding, which use SS 304 as the default and SS 316 for coastal and sea-facing work.

A short history of stainless steel

Steel rusts because iron reacts with oxygen and water. For centuries the only defences were paint, oil, tin or zinc coatings. In the early twentieth century metallurgists in Britain and Germany discovered that adding enough chromium to steel changed its behaviour completely. In Sheffield in 1913, Harry Brearley produced a steel with about 12–13 per cent chromium that resisted staining by acids, and it was soon being made into cutlery. Around the same time, work at Krupp in Germany produced steels containing both chromium and nickel, which formed the basis of the austenitic family that includes today's 304 and 316.

Through the twentieth century the family grew. Molybdenum was added to create 316, which resists chlorides far better and became the standard for marine, chemical and medical uses. When nickel was scarce or expensive, manufacturers developed the 200 series, in which part of the nickel is replaced by manganese and nitrogen; this kept the steel austenitic and formable at a lower cost. India became one of the world's major producers and users of stainless steel, and 200-series grades became widely used for utensils, budget kitchenware and fabrication, which is why the 202-versus-304 question is so familiar in Indian markets.

Why stainless steel does not rust — and when it does

Stainless steel contains at least about 10.5 per cent chromium. The chromium reacts with oxygen in the air to form an extremely thin, invisible film of chromium oxide on the surface. This passive layer stops further corrosion, and — unlike paint — it repairs itself when scratched, as long as oxygen is available. That is why a scratched stainless sink does not rust while a scratched painted mild steel trolley does.

The passive layer has enemies. The most important are chlorides: salt in sea air, salt in cooking, chlorine in pool water and some cleaning products, and hydrochloric acid used to clean tiles. Chlorides attack the passive layer at weak points and cause pitting — small, deep pits that show as rust spots — and crevice corrosion in tight gaps such as under washers or between overlapping parts. Other enemies are iron contamination (particles from mild steel tools, grinding discs or steel wool embedded in the surface, which rust and look like the stainless is rusting), heat tint from welding that has not been cleaned and passivated, and lack of rain-washing on sheltered outdoor surfaces where salts accumulate.

The three grades differ in how well their passive layer resists these attacks. More chromium helps; molybdenum helps a great deal against chlorides; nickel stabilises the austenitic structure and improves toughness and formability. Manganese, used in 202 to replace nickel, keeps the steel austenitic but does not add corrosion resistance, and manganese-rich inclusions in the steel can act as starting points for pits. Engineers compare chloride resistance using the Pitting Resistance Equivalent Number (PREN = %Cr + 3.3 × %Mo + 16 × %N): 304 typically scores about 18–21 and 316 about 23–28. The practical ranking that follows from metallurgy and field experience is clear — 316 is better than 304, and 304 is clearly better than 202.

What is inside 202, 304 and 316

The table gives the nominal composition ranges commonly specified for sheet and plate under international standards such as ASTM A240, with equivalent Indian grades under IS 6911. Exact limits vary slightly between standards and product forms, and a mill test certificate gives the actual analysis of a particular batch.

How the grades compare in use

In a dry, air-conditioned interior, all three grades will usually look good for years. The differences appear as soon as moisture, salt, heat or chemicals are involved. Indian kitchens are harsh: steam, salt, tamarind and lemon, detergents, and frequent wiping. Bathrooms combine humidity with cleaning chemicals. Balconies and terraces in Surat, Mumbai, Chennai or Kochi see humid, salty air for most of the year. Pools add chlorine. The comparison below is general guidance drawn from metallurgy and common fabrication practice, not a guarantee for every product; finish quality and maintenance matter almost as much as grade.

The magnet test myth

Many buyers in India hold a magnet to a sink or railing and conclude that if it does not stick, the steel is 304. This test is useful for one thing only: separating austenitic stainless steel from strongly magnetic materials — mild steel, chrome-plated mild steel, and ferritic stainless grades such as 430. As this site's kitchen trolley guide explains, a firm grab across the whole surface proves the item is not 304. But 202 is also austenitic and is essentially non-magnetic in the annealed condition, so a magnet cannot tell 202 from 304 — and both can show a slight attraction at bends and welds because cold working changes their structure. Equally, a magnet cannot tell 304 from 316. The test eliminates fakes; it does not confirm a grade.

Which grade belongs where

The simplest rule Aaditya Interior uses on projects is: 304 by default, 316 wherever salt or chlorine is present, and 202 only where the item is dry, indoors, decorative and cheap to replace. The table turns that into a schedule that can go into a specification or a purchase order.

Railings: the most common stainless decision

Railings are where most Indian homeowners and builders choose a stainless grade, and where the consequences are most visible. A typical stainless balcony or staircase railing uses a round or square handrail of about 38–50 mm, posts at about 1000–1200 mm centres fixed with base plates and anchors, and infill of vertical balusters, toughened glass or cable. The guard height for balconies follows the 1000–1100 mm band used throughout this site's railing guides, with gaps under 100 mm and no climbable horizontal rails — the classic three-pipe horizontal railing is a ladder for children and should be avoided where children live.

Material thickness matters as much as grade. Very thin tube — common in cheap railings — dents easily, flexes under load and is harder to weld well. For domestic railings, handrail and post tubes in the region of 1.2–2 mm wall are common, with heavier sections or solid posts where glass or long spans are involved. The structural adequacy of a railing — post spacing, base plate size and anchor type — should be checked by the engineer, particularly on balconies and for glass infill. Fixings should be in the same or a better grade than the railing: a 316 railing on mild steel bolts will rust at every base plate.

Finishes, fabrication and cleaning

Grade is only half of the story. A smooth, well-finished surface resists corrosion better than a rough one, because salts and dirt have fewer places to sit. Common finishes are the mill finishes 2B (smooth, matt grey) and BA (bright annealed, reflective), the brushed No. 4 and the longer-grained hairline finish used on railings and lift cladding, and the mirror No. 8 finish used for decorative work. Coloured finishes such as gold, rose gold and black are usually PVD coatings applied on 304; the coating is thin and decorative, so the base grade still decides how the item behaves when the coating is scratched. On exteriors, brushed lines should run vertically so that rain can wash them, and horizontal ledges that hold water should be avoided.

Fabrication quality is critical. Welds leave a coloured heat tint whose passive layer is weakened; on good work, welds are ground smooth, then pickled and passivated (chemically cleaned) to restore corrosion resistance. Low-carbon 304L and 316L are preferred for welded work in thicker sections. Tools used on mild steel — grinding discs, wire brushes, cutting wheels — must not be used on stainless, because embedded iron particles rust and stain the surface. On building sites, the commonest cause of sudden rust on new stainless railings and sinks is hydrochloric (muriatic) acid used to clean cement from tiles; it attacks stainless steel quickly, so stainless items should be covered or installed after acid cleaning.

Cleaning is simple but often done wrong. Warm water with a mild detergent and a soft cloth or nylon pad cleans all three grades. Wiping in the direction of the brush lines keeps the finish even. Rinsing with fresh water and drying prevents water spots and removes salts. Chloride bleach left standing on stainless, acid tile cleaners and steel wool all damage the passive layer or embed iron. Outdoors near the sea, rinsing railings with fresh water every few weeks — more often where rain does not reach — prevents the brown tea staining that otherwise appears even on 316. Light tea staining is a surface discolouration and can usually be removed with a stainless cleaner; deep pitting cannot.

What each grade costs in October 2026

Stainless prices in India move with the global nickel and molybdenum markets, so the figures below are indicative and should be confirmed with a dealer on the day of purchase. The railing and accessory ranges for 304 are the same as those used across this site; ranges for 202 and 316 railings are estimates based on typical material price differences. Installed railing prices depend heavily on design, thickness, glass and quantity.

The cost difference between grades is often smaller than it appears once labour, design and installation are included. On a typical 30 running ft balcony railing, the step from 304 to 316 might add a modest share to the total, while a corroding 202 railing on a coastal balcony may need replacement within a few years. For small, hidden and critical parts — screws, anchors, hinges and cramps — the cheapest option is almost always the most expensive in the long run.

Where stainless steel is heading

Three developments are worth watching. Duplex stainless steels, which combine austenitic and ferritic structures, offer higher strength and better chloride resistance than 316 and are increasingly used for structural and coastal applications where 316 is marginal. Stainless steel rebar and anchors are being used in a few highly exposed concrete structures where long life justifies the cost. And the industry is publishing more data on recycled content and carbon footprint, since stainless steel is highly recyclable. For homes, the practical trend is simpler: buyers are learning to ask for the grade in writing, more fabricators are offering analyser checks, and 304 is becoming the floor rather than the ceiling for anything wet.

Rules for specifying stainless steel

• Specify 304 by default for kitchens, bathrooms, trolleys, railings and hardware; never write just SS.
• Use 316 on sea-facing and coastal sites, near pools, and where salt or chlorine is present.
• Limit 202 to dry, indoor, decorative items that are cheap to replace.
• Use fasteners of the same or a better grade than the item they fix — A2 for 304, A4 for 316.
• Ask for a mill test certificate, or an analyser check on site, for railings and large orders; do not rely on a magnet.
• Choose smooth finishes and design out water traps, crevices and horizontal ledges outdoors.
• Insist that welds are ground, pickled and passivated, and that mild steel tools are kept off stainless.
• Protect stainless items from acid tile cleaning, or install them after it is finished.
• Clean with mild detergent and fresh water; rinse coastal railings regularly.

Frequently asked questions

What is the difference between SS 202 and SS 304?

Both are austenitic stainless steels with similar chromium, but 202 replaces about half of 304's nickel with manganese and nitrogen. That makes 202 cheaper, but noticeably less resistant to corrosion in humid, salty or chemical environments. In Indian kitchens, bathrooms and outdoors, 304 lasts far longer; 202 is acceptable only for dry, indoor, decorative items.

Is SS 316 better than SS 304?

For corrosion resistance, yes: the 2–3 per cent molybdenum in 316 gives much better resistance to chlorides from sea air, salt and pool water. For most inland homes, 304 is entirely adequate and costs less. Use 316 on coastal and sea-facing sites, near swimming pools and in heavy salt or chemical use.

How can I check whether steel is 304 or 202?

A magnet cannot do it, because both grades are essentially non-magnetic. Ask for the grade in writing on the quotation and invoice, request a mill test certificate with the heat number, and for railings or larger orders ask the supplier to check the material with a handheld XRF analyser. Chemical spot test kits can indicate nickel or molybdenum content as a rough check.

Which stainless steel is best for railings?

SS 304 for interior and inland exterior railings, and SS 316 for coastal or sea-facing balconies and pool areas. Use fixings of the same or better grade, a smooth finish, and adequate tube thickness, and keep the railing at the 1000–1100 mm guard height with gaps under 100 mm.

Why is my stainless steel sink or railing rusting?

The usual causes are a lower grade than claimed (often 202), iron particles from mild steel tools or steel wool, acid tile cleaner used nearby during construction, unpassivated welds, or salt deposits on sheltered surfaces near the sea. Light surface rust and tea staining can often be removed with a stainless cleaner; persistent pitting usually means the grade is wrong for the environment.