304 vs 202 Stainless Steel, Tri-Ply & Knives

Search for “304 vs 202” and most of the answers come from companies selling sinks and steel sheet. They disagree with each other, especially about whether a magnet can tell the two apart. So we went to the organisations that actually set the rules and study the metal: the Bureau of Indian Standards, the Australian and British stainless steel associations, the International Stainless Steel Forum, steelmakers’ datasheets and peer-reviewed research.

Here is what the numbers on your kitchenware mean, which steel ends up in which product, and which home tests work.

What makes steel “stainless”

Ordinary steel is mostly iron, and iron rusts. Stainless steel adds chromium. When chromium meets the oxygen in air, it forms a very thin, invisible layer of chromium oxide over the surface. That layer keeps air and water away from the iron underneath. If you scratch it, it grows back by itself.^[1] Think of it as a raincoat that repairs its own holes.

Two rules follow, and they explain most of this guide:

• More chromium means a stronger raincoat. Steel with less chromium rusts, stains and pits more easily.^[1]
• Other ingredients change how the steel behaves. Adding nickel (or cheaper manganese) makes steel soft enough to press into a deep pot, and it stops the steel sticking to a magnet. Adding carbon and heat-treating the steel makes it hard enough to hold a knife edge.^[1],[3]

The four kinds of steel in an Indian kitchen

Almost every steel item you own belongs to one of four families. The numbers people argue about (304, 202, 430, 420) are just names for recipes inside these families.

Sources for the table: 304^[2], 200 series^[4],[6], 430^[3],[8], knife steels.^{[18],[19],[20],[21]}

304 vs 202: what is actually different

Here are the official recipes side by side. The last two rows are grades developed and standardised in India specifically for utensils.

Sources: 304, 201 and 202^[1],[4], J4^[4], IS 15997.^[6]

Why use less nickel at all? Money. Nickel is the most expensive ingredient in stainless steel. When a nickel shortage in the late 1980s led the Indian government to cut nickel imports, Indian mills switched to the manganese recipes on a huge scale.^[1] That is why so much everyday Indian tableware is 200-series steel.

What you give up is rust resistance, not safety. Manganese can replace nickel’s job of keeping the steel soft and non-magnetic. But the less nickel a recipe has, the less chromium it can hold, and chromium is what fights rust.^[1],[4] Steel industry tests found:

• In a 575-hour salt-spray test, low-nickel samples showed significant corrosion. The 304 sample did not.^[1]
• In acidic conditions, a 1%-nickel grade corroded ten times faster than 304 inside narrow gaps and crevices.^[1]

In everyday use this shows up as rust spots, tiny pits and brownish stains, not as a pot falling apart. The European steel association notes that in India these grades have “proved entirely adequate” for tableware, mainly because it is washed by hand rather than in a dishwasher.^[5] The International Stainless Steel Forum reports good experience with 200-series cookware containing at least 16% chromium, but says the lowest-nickel grades should avoid strongly acidic conditions (below pH 3).^[1]

Is 202 safe to cook in? Nothing we found from standards bodies or steel associations treats it as a food-safety risk. The concern in every document we analysed is corrosion. India even has a standard written for low-nickel utensil steel (IS 15997), and the Indian utensil standard, IS 14756, allows utensils to be made from it.^[6],[7] There is one extra rule: parts made of low-nickel steel that touch food must not be welded.^[7]

What about nickel in your food?

Stainless steel is not completely inert, whatever the grade. Oregon State University researchers simmered tomato sauce with 304 and 316 steel for 6 to 20 hours. Brand-new steel released the most nickel and chromium into the sauce. The amount fell with each cook and levelled off after about the sixth, though it never dropped to zero.^[15] For most people this doesn’t matter. The authors suggest that people who are allergic to nickel may be wise to avoid stainless cookware.^[15] The closest everyday Indian case is a long-simmered sour gravy, such as tamarind or tomato, in a brand-new pot.

What 18/8, 18/10 and 18/0 mean

These numbers are older, friendlier names for the same grades. The first number is roughly the percentage of chromium and the second the percentage of nickel.^[3]

• 18/8 is 304. “SS 304” and “18/8” on two listings mean the same steel.^[3]
• 18/10 is also 304. The British Stainless Steel Association says the “10” “does not indicate an actual higher Ni content and is purely a marketing ploy.”^[3] Don’t pay extra for it.
• 18/0 is 430. It has almost no nickel, it sticks to a magnet and it resists rust less well than 304. The chromium is also “nearer 17%” than 18.^[3]

Does the magnet test work?

No, not for 304 vs 202. This is the most common myth online, so here is exactly what a fridge magnet tells you:

• 304 and 202 both ignore a magnet. The steel industry’s own test chart lists “not attracted” for both families.^[10] The Australian association puts it bluntly: 200-series steel is “often assumed to be 304”, and “magnetism has no relationship to corrosion resistance.”^[4]
• A weak pull does not mean fake 304. Genuine 304 becomes slightly magnetic where it has been bent, pressed or stretched hard, such as a rolled rim or a deep-drawn tumbler.^[2],[9] The same happens to 200-series steel.^[10]
• A strong pull means 430, a knife steel, or ordinary plated steel. 430 and knife steels are magnetic by nature.^[3],[9] On a thali, a strong pull tells you the item is not 304 or 202.

What a magnet is good for: checking that a pan will work on induction. Induction needs a magnetic base, which is why Indian standards specify 430 steel, a magnetic grade, for the induction plate or outer layer of cookware.^[3],[11] If a magnet grips the base firmly, the pan should heat on induction.

How to check the grade at home: what works and what doesn’t

Step 1: read the marking

This is the check that actually works for most people:

• ISI-marked utensils must show their grade. The Indian utensil standard, IS 14756, requires every utensil to show its material grade, by stamping or engraving, or on the packaging or a sticker.^[7] Keep the box.
• But the ISI mark on a utensil does not mean 304. IS 14756 accepts steel from IS 5522 (which covers 304, 302 and 430) or from the low-nickel standard IS 15997.^[7],[8] The mark means the utensil met the standard. The grade printed next to it tells you which steel it is.
• ISI on utensils is optional again. A 2024 government order set out to make the ISI mark compulsory for stainless steel utensils.^[13] The replacement order of January 2026 covers aluminium utensils and cans, but stainless steel utensils were dropped from the compulsory list.^[14] Many steel utensils in shops will carry no ISI mark and no grade at all.
• A listing claim is not a marking. “SS 304” in an Amazon bullet is the seller’s statement. A stamp on the metal or an ISI-certified grade on the box carries more weight.

Step 2: know what an ISI mark guarantees on cookers and flasks

For two products, the Indian standard itself limits which steel can be used. This is more useful than any home test.

• Pressure cookers (IS 2347). A single-layer stainless cooker body must be 304-type steel or one specific low-nickel grade (X8Cr16Mn8Cu2Ni2N, which has about 16% chromium and 8% manganese).^[11] So an ISI mark on a plain steel cooker does not prove 304. A tri-ply ISI cooker, however, must have 304 on the inside.^[11]
• Vacuum flasks and bottles (IS 17526). The inner wall, which touches your drink, must be 304 or better. The outer shell may be a low-nickel grade. Both grades must be permanently marked on the flask.^[12] Look at the base.

That is why we give so much weight to ISI certification in our insulated water bottle and pressure cooker roundups.

Tri-ply vs ordinary stainless steel

Stainless steel is good at resisting rust and bad at spreading heat. 304 conducts heat at about 16 W/m·K.^[2] Aluminium conducts at about 222, roughly 13 times faster.^[16] In a single-layer steel pot, the heat stays in a patch above the flame. That is where milk catches and dal sticks.

Tri-ply (also written triply or 3-ply) solves this by bonding three layers into one sheet. Indian standards spell out the recipe:^[7],[11]

• Inside: 304 steel, the layer that touches food.
• Middle: aluminium, which spreads heat quickly across the base and up the sides.
• Outside: 430 (or 439) steel, which is magnetic, so the pan works on induction.

Hawkins describes its tri-ply cooker the same way: an 18/8 food-grade interior, a heat-diffusing core and an AISI 430 magnetic exterior, 3 mm thick in total.^[17]

Full-body tri-ply vs a tri-ply base

Read listings carefully. “Tri-ply” can describe the whole body or just the bottom:

The Hawkins is tri-ply all the way up the sides. The Prestige has a 304 body with a tri-ply base only. That spreads heat across the bottom, where most scorching happens, but the walls are a single layer. Both are reasonable designs. They are just not the same thing.

Stainless steel pressure cooker vs tri-ply: which to buy?

• Choose tri-ply if you cook a lot of milk-based dishes, thick dals or anything that scorches, or if you want the same even heating on gas and induction. It is also the only stainless cooker type where an ISI mark guarantees 304 on the inside.^[11]
• A single-layer steel cooker with a good composite base is fine for everyday dal and rice, and costs less. Check the listing names the grade (304/18/8) and that it carries ISI.

In our stainless steel pressure cooker roundup, the Hawkins 5L Triply Contura is our top pick, largely for the full-body construction quoted above.

Knife steels: why good knives are “less stainless”

A knife has a different job from a pot. It needs to be hard, so its thin edge doesn’t bend or wear down quickly. Nickel steels like 304 can’t be hardened by heat treatment, so they can’t hold a sharp edge. That is why the best table knives pair an 18/8 handle with a separate, harder blade.^[3]

Knife blades use martensitic stainless steel: chromium plus carbon, heated and quenched to make it hard. Victorinox says it uses this steel “because it can be hardened, which is a must to create strong blades and tools.”^[24] The trade-off is that these steels have less protection against rust than 304, and all of them stick to a magnet.^[3],[9]

The main dial is carbon. More carbon lets the steel be hardened further:

Sources: 410^[18], 420/3Cr13^[19], X50CrMoV15^[20],[22], 440C.^[21]

Hardness is measured on the Rockwell C scale (HRC); a higher number means harder. WÜSTHOF hardens its X50CrMoV15 blades to 56–58 HRC,^[23] while 440C can reach about 60.^[21] WÜSTHOF describes that range as a balance between durability and ease of sharpening.^[23] Harder steel holds an edge longer but takes more effort to sharpen.

“3Cr13” on a listing is the Chinese name for the 420-type steel in the second row. The steelmaker’s datasheet lists it as the equivalent of X30Cr13, AISI 420 and Japan’s 420J2.^[19] It is the usual budget blade steel. It is fine for home cooking. It has less carbon than German knife steel or 440C, so it can’t be hardened as much, and it needs drying after washing.

Naming the steel is a good sign; many sets only say “high carbon stainless steel”, which tells you nothing. But “no rust, stains or pitting” oversells any knife steel, because martensitic blades trade some rust resistance for hardness.^[3] Our knife set roundup explains which sets hold an edge and which are mostly filler.

To keep any steel knife looking new: wash it by hand, dry it straight away, and don’t leave it wet in the sink. These steels rust more easily than 304, so a small spot after a knife was left wet does not, by itself, mean it is fake.

Which steel goes where: a quick map

A 60-second checklist before you buy

1. Find the grade. Look for “304”, “18/8” or “SS 304” stamped on the item, printed on the box, or in the listing’s specifications. If no grade is given anywhere, assume it could be 200-series.
2. Treat 18/10 as 304. It is not a higher grade.^[3]
3. Skip the magnet test for 304 vs 202. Use a magnet only to check induction compatibility.^[10]
4. For cookers and flasks, prefer ISI, and remember what it does and doesn’t guarantee: 304 inside a tri-ply cooker or a flask, but not necessarily in a plain steel cooker.^[11],[12]
5. Check whether tri-ply means the whole body or just the base.
6. For knives, look for a named steel (420/3Cr13, X50CrMoV15, 440C) and expect to dry them after washing.
7. Nickel allergy? Consider this when buying new stainless cookware for long-simmered sour dishes, and talk to your doctor.^[15]