How to Identify Real 304 Stainless Steel
A field-test buyer's guide to telling genuine 304 from carbon steel, look-alike 201 and mislabelled stock. Each test is explained honestly — what it detects, how to run it, what the result means, and where it fails. The short version: field tests are screening only; the reliable proof is a mill test certificate plus a reputable supplier.
Why "is it stainless?" and "is it 304?" are two different questions
Most quick tests answer only the first question — they separate stainless from plain carbon steel. Telling 304 apart from 201 (a cheaper, higher-manganese, lower-nickel austenitic grade that looks identical) is much harder, because the two share the same bright, non-magnetic appearance. The single most common substitution in the trade is 201 sold as 304, and no magnet or eyeball test reliably catches it. Read each method below for what it can and cannot prove.
If you only remember one thing: a magnet does not separate 201 from 304, and a handheld analyser cannot read carbon. Match the test to the question you are actually asking. For the underlying compositions, see our stainless steel grades reference.
The magnet test
The most popular and most misunderstood test. Useful, but only for ruling out certain things — never for confirming 304.
Stainless steel test solutions (spot reagents)
Chemical "identifying solutions" — sometimes sold as a "304 vs 201 test reagent" — are the most practical chemical screen for separating austenitic grades, when used correctly.
The copper sulfate test
The quickest way to separate any stainless steel from plain carbon steel — but blind to grade.
The nitric acid test
A classic sorting test based on stainless steel's resistance to concentrated nitric acid. Effective at separating stainless from carbon steel, but genuinely hazardous — treat it as a professional method.
The spark (grinding) test
Indicative only — useful to a trained eye for sorting scrap families, not for confirming a grade.
Instrument and laboratory verification
When you need to prove the grade rather than screen it, you move from kitchen-table tests to instruments — and ultimately to documentation.
Which test answers which question?
Use this to pick the right test — and to see, plainly, that only instruments and certificates can confirm 304 over 201.
| Test | What it detects | Can it tell 304 from 201? | Reliability |
|---|---|---|---|
| Magnet | Ferromagnetism (rules out ferritic/martensitic & carbon steel) | No — both are non-magnetic | Low (screening only) |
| Molybdenum spot reagent | Presence of Mo (flags 316) | No — neither has Mo | Low for 304/201; useful for 316 |
| Manganese / low-Ni reagent | High manganese, low nickel (flags 201) | Indicative yes — colour reaction | Moderate (screening, qualitative) |
| Copper sulfate | Free iron (stainless vs carbon steel) | No | Low for grade; good stainless screen |
| Nitric acid | Acid resistance (stainless vs carbon steel) | No | Low for grade; hazardous |
| Spark (grinding) | Carbon content / family | No | Low (subjective) |
| Handheld XRF | Elemental % (Cr, Ni, Mn, Mo …) | Yes | High (but no carbon → can't split 304/304L) |
| OES / lab spectrometry | Full composition incl. carbon | Yes | Very high (reference method) |
| MTC (EN 10204 3.1/3.2) | Documented heat chemistry & traceability | Yes | High — best practical buyer proof |
Field tests screen; certificates and a reputable mill confirm
Quick tests have their place — they cost almost nothing and catch obvious carbon-steel or 201 substitutions before money changes hands. But every one of them is a screen, and the most common fraud (201 sold as 304) is exactly the one a magnet and most spot kits cannot settle on their own.
- Use field tests to flag problems early: magnet to rule out 400-series/carbon steel, copper sulfate or nitric acid to rule out carbon steel, a manganese reagent to flag suspected 201.
- Demand the mill test certificate — ideally EN 10204 3.1 — and check the reported chemistry against the standard for 304 (e.g. ASTM A312/A213 or your applicable spec).
- For high-stakes or disputed lots, verify with handheld XRF (for the alloying elements) or send a sample for independent OES/lab analysis (which also reads carbon for L-grades).
- Above all, buy from a manufacturer that traces every heat and is willing to put the grade in writing.
How we make 304 verifiable — and sell 201 honestly
ZAIHUI is a manufacturer-direct stainless steel mill in Foshan, producing since 2006 across 130+ production lines. The way we keep grade honest is documentation and traceability, not a sales claim.
FAQ
Can a magnet tell real 304 from fake or from 201?
No. A magnet only separates magnetic steels (ferritic/martensitic grades like 430 and 410, and carbon steel) from non-magnetic austenitic grades. Both 304 and 201 are austenitic and largely non-magnetic when annealed, so a "non-magnetic" result is consistent with either one. Cold-worked or welded material can also pick up slight magnetism locally. The magnet test is a useful screen to rule out 400-series and carbon steel, but it cannot confirm 304 or distinguish it from 201.
What is the most reliable way to confirm a grade is really 304?
Documentation plus instruments. The most practical buyer proof is the mill test certificate (ideally EN 10204 3.1, which reports lot-specific chemistry signed by the manufacturer's QA, or 3.2 with third-party witnessing), checked against the standard chemistry for 304. For verification, a handheld XRF analyser reads the alloying elements (Cr, Ni, Mn, Mo) in seconds, and an independent OES/lab analysis confirms the full composition including carbon — the only way to separate 304 from low-carbon 304L. Field tests alone are screening, not confirmation.
Why can't a handheld XRF tell 304 from 304L?
304 and 304L have essentially the same chromium, nickel and manganese; they differ mainly in carbon content (304L is the low-carbon version). Handheld XRF cannot measure carbon — carbon sits far below the light-element range any handheld unit can read — so it cannot split 304 from 304L. XRF is excellent for separating 201, 304 and 316 by their heavier alloying elements, but confirming an "L" grade requires OES or laboratory chemical analysis, which read carbon directly.
Is it safe to do the nitric acid or reagent tests myself?
Only with proper training and precautions. Concentrated nitric acid is highly corrosive and toxic and gives off dangerous brown fumes; spot reagents are also corrosive. If you run them, use full PPE (chemical gloves, eye/face protection, apron), work in a fume hood or well-ventilated area, never inhale the fume, keep neutralising agents available and follow each product's safety data sheet. If you are not trained to handle strong acids, skip these and instead ask the supplier for a mill test certificate or send a sample to an accredited lab.
Verify, compare and buy
Want 304 you can verify?
Ask ZAIHUI for a quote with the mill test certificate, run XRF on receipt, and check the chemistry against the standard. Honest grade, every heat documented.