201 vs 304 Stainless Steel: What to Put on the Spec Sheet

A hotel in Dubai reorders vanity handles because the first batch shows brown spots after one humid summer. The factory's answer is technically true and commercially useless: "the material is stainless." It is. It is grade 201, and 201 is not the grade that survives salt air on a bathroom door.

201 vs 304 stainless steel is usually argued as a price question. On a furniture or hardware spec sheet it is a corrosion question, and the two grades only look interchangeable until the part lives somewhere wet, warm or within reach of the sea. Below is the comparison buyers actually run, the field test that separates them, and the lines to add to your spec sheet so nobody has to guess which one you shipped.

201 vs 304 stainless steel: the comparison buyers run

Read the composition row as the whole story: the two grades are not distant cousins with different marketing. 201 buys its lower price by replacing most of the nickel with manganese, and nickel is one of the two elements doing the corrosion work. Acerinox and Aperam both publish the 1.4372 chemistry if a buyer wants it from a mill rather than from you.

Why the nickel number, not the label, decides the failure

Stainless steel resists rust because chromium forms a thin oxide layer that heals itself. Nickel does a different job: it holds the austenitic structure together and raises general corrosion resistance, particularly in chloride. Take roughly half the nickel out and add manganese, and you still have a bright, non-magnetic, weldable metal that passes a visual inspection and machines beautifully. What you no longer have is margin.

That margin is spent at the places a buyer never photographs: the sheared edge of a bracket, the weld on a towel rail, a scratch on a handle that traps salt, the underside of a rail where water sits. Pitting starts in those crevices, and once a pit opens it keeps going. The practical consequence is that 201 and 304 behave almost identically in a dry inland showroom and diverge sharply in a bathroom, a pool deck or a beachfront villa.

Two honest caveats. First, 304 is not immortal either. In genuinely aggressive chloride, 316 is the grade that belongs there, and the step from 304 to 316 is the same argument one price band up. Second, none of this makes 201 a bad material. It is a legitimate cost decision for indoor, dry, decorative hardware. The failure is never the grade. The failure is shipping it silently into an environment it was not chosen for.

The magnet test is not a grade test

Every week a buyer opens a carton, touches a magnet to a handle, and concludes something. Usually the wrong thing.

Both 200-series and 300-series austenitic grades are effectively non-magnetic in the annealed condition. The British Stainless Steel Association puts the permeability of annealed austenitic steel at around 1.0 — a hand magnet does nothing. Cold working changes that: forming, drawing, shearing and machining can partially transform austenite to martensite, which is ferromagnetic, so a cold-drawn bar or a sheared edge can pull a magnet. The association notes this applies to conventional 300 grades and to 200 grades alike.

So a magnet answers one question only: was this part cold worked, and how hard? It cannot tell 201 from 304. What does separate them in the field is a manganese spot test — a drop of reagent that turns colour on 200-series steel by definition and stays clear on 300-series steel, as the Australian Stainless Steel Development Association sets out in its grade-confirmation guide. Fasteners escape this problem because their grade is stamped on the head — the logic behind A2-70 vs A4-80 stainless bolt marking — but a furniture handle rarely carries a stamp, which is why the sheet has to.

Two rules if you use spot tests. They mark the surface, so test an inconspicuous area, and they are qualitative — enough to catch a substitution, not enough to certify a heat. For certification, ask for the mill's EN 10204 type 3.1 certificate and check that the heat number on it matches the parts, then run a positive material identification (PMI) check if the consequence of being wrong is expensive. What a mill test certificate 3.1 vs 2.2 actually proves is a subject of its own.

Where 201 fails first

The failure is almost always chloride plus time, and the geography matters more than most spec sheets admit. ASSDA's guidance on coastal corrosion is blunt: tea staining — surface discolouration from corrosion — occurs most commonly within about five kilometres of the surf, gets worse closer to the marine source, and can appear 20 kilometres or more inland where wind exposure, humidity and pollution combine against the steel.

That is 304's problem, not 201's alone. For 201 the same conditions arrive earlier and bite harder, because the pitting resistance is lower to begin with. The 201 vs 304 stainless steel decision is therefore an environment decision wearing a metallurgy costume. Rank the environments rather than the grades:

• Dry interior, temperature controlled: 201 is a defensible choice for decorative hardware and low-load trim. Nobody will ever know.
• Bathroom, kitchen splash zone, indoor pool hall: 304 is the floor, and 316 is the better answer where chlorinated water or cleaning chemicals are constant.
• Within a few kilometres of salt water, or on an exposed balcony: skip 201 entirely; 304 at minimum, 316 for anything a buyer will touch and inspect.
• Road-salt climates: the same logic as the coast, applied to the lower half of a door or the legs of a trolley.

What to declare on the spec sheet

Most arguments about grade start because the spec sheet says "stainless steel" and nothing else. Give the buyer a block they can compare against another supplier's, and the argument moves from opinion to a document.

That last line is the one worth fighting for. A substitution clause converts a surprise into a decision, and a decision can be priced. It also gives your own QC something to enforce when a factory runs short of 304 on a Friday.

One more line belongs next to the part itself, not only in the table: the grade, on the photo, where the buyer already looks. A spec sheet is read once by one person; an annotated product image travels into the buyer's WhatsApp thread, their comparison sheet and their complaint. The measured callout that carries a part number and a material grade is the same callout that carries a dimension — the layout an industrial spec diagram already uses for fittings and hardware — and it is the version a buyer forwards.

A worked example: three markets, one handle

Same handle, same drawing, three destinations. What changes is one line on the spec sheet and one line in the price.

Buyers running multi-market programmes will often accept a split BOM — 201 for the domestic line, 304 for the export line — if the spec sheet makes the difference visible. They will not accept discovering it from a rust complaint six months later.

Check a sample before the container ships

• Mill certificate for the heat, EN 10204 type 3.1, heat number legible
• Heat number on the certificate matches the parts or their packaging
• Grade declared on the drawing with UNS and EN designations, not "SS201"
• Manganese spot test on an inconspicuous area of one part per lot
• Finish recorded (2B / BA / No. 4) and checked against the sample
• Welds dressed, pickled or passivated where the finish calls for it
• Intended environment written on the spec sheet, not assumed
• Substitution clause present in the PO
• Same grade and finish stated on the photo callout, the table and the catalog

FAQ

Is 201 stainless steel good for furniture?

Yes indoors, no near water. 201 is an austenitic grade that replaces most of its nickel with manganese, which is fine for dry, decorative hardware and trim, and weak in bathrooms, kitchens and coastal sites where chloride drives pitting. Decide by the environment the part will live in, then write the grade down.

Does a magnet stick to 304 stainless steel?

Not to annealed 304, and sometimes slightly to cold-worked 304. Cold forming, drawing, shearing and machining can create martensite at edges and surfaces, and that phase is magnetic. The British Stainless Steel Association puts annealed austenitic permeability at around 1.0, so a magnet tells you about the forming history, not the grade.

What is the nickel difference between 201 and 304?

ASTM A240 gives 201 a nickel range of 3.5–5.5% and 304 a range of 8.0–10.5%. 201 compensates with manganese at 5.5–7.5%, where 304 allows 2.0% at most. That single substitution is where the price gap and the corrosion gap both come from.

How can I tell if a supplier substituted 201 for 304?

Ask for the EN 10204 type 3.1 mill certificate and match the heat number to the parts, then confirm with a manganese spot test on a hidden area — 200-series steel reacts, 300-series does not. A magnet will not answer the question, and neither will a mirror finish.

Sources & References

• ASTM A240/A240M — chromium and chromium-nickel stainless steel plate, sheet and strip
• Acerinox — EN 1.4372 / AISI 201 chemical composition
• British Stainless Steel Association — cold work and the magnetic permeability of austenitic stainless steels
• ASSDA Technical FAQ 4 — testing for grade confirmation
• ASSDA Technical FAQ 3 — magnetic effects of stainless steels
• ASSDA Technical FAQ 6 — preventing coastal corrosion (tea staining)