How to Identify SS 304 and SS 202: Tests That Work

SS 202 and SS 304 are both austenitic stainless steels and look the same when polished. The difference is chemistry: 202 has roughly half the nickel of 304 and several times the manganese. Identification therefore comes down to measuring nickel and manganese, either on paper through a certificate or in the metal with an analyser. Why the difference matters for a railing is covered in SS 202 vs SS 304 railing; this page is about checking what you have been sent.

SS 202 vs SS 304 chemical composition

So the SS 202 nickel percentage is 4 to 6 %, against 8 to 10.5 % in SS 304. Manganese and nitrogen make up for the missing nickel in 202, which keeps the steel austenitic at a lower cost but with weaker corrosion resistance.

One caution: material sold in the market as "202" is often a still leaner 200-series variant with less nickel than the standard range. A reading well under 4 % nickel with high manganese is common and points to that kind of steel.

Why the magnet test does not work

The magnet test is the one everybody tries, and it cannot separate these two grades.

• Both 202 and 304 are austenitic, and austenitic stainless steel is essentially non-magnetic when annealed.
• Cold working changes that. Bending, drawing, rolling a tube and heavy polishing can all leave either grade slightly magnetic, most noticeably at corners and bends.
• So a weak pull does not prove the steel is 202, and no pull does not prove it is 304.

What a magnet can do is flag a different material altogether. A strong, firm pull means mild steel or a ferritic stainless such as 430, not an austenitic grade. That is useful for telling a plated or painted MS railing from stainless, and for nothing finer than that.

Methods that work, ranked by reliability

1. Mill test certificate (MTC). The steel mill issues a certificate for each heat, listing the measured composition and the heat number. Ask for it with the delivery and check three things: the nickel and manganese figures fall in the ranges above, the heat number on the certificate matches the marking on the tube or sheet, and the certificate names the mill. A certificate that cannot be tied to the material by a heat number is only a piece of paper.
2. Handheld XRF, also called PMI testing. An X-ray fluorescence analyser is pressed against the metal and reads chromium, nickel, manganese and molybdenum in a few seconds without damaging the part. Testing laboratories and inspection agencies offer it, and many scrap dealers and steel stockists keep a gun because they buy by grade. This is the only quick test that measures the piece in your hand, so it is the best check on a certificate.
3. Chemical spot-test kits. A manganese kit puts a drop of reagent on a cleaned patch and shows a colour change on high-manganese 200-series steel. A separate molybdenum kit distinguishes 316 from 304. Kits are cheap and portable. They show which family the steel belongs to but give no percentages, and the surface must be clean bare metal for a fair result.
4. Grade stamp or ink marking. Tubes and sheets from organised mills usually carry a printed grade, size and heat number. It is worth looking for, but a marking can be absent on cut lengths and small fittings, and it is easy to imitate.
5. Price sanity. Nickel is the costly ingredient, so genuine 304 cannot be sold at 202 rates. If one quotation for "304" is far below the others, ask what explains it. Price is a warning sign and never proof.

The certificate tells you what the mill made. The XRF reading tells you what arrived. For a large order, use both.

What you cannot rely on

• Colour and shine. A polished 202 sample is as bright as 304.
• Weight. The densities are too close to feel or to weigh on site.
• Waiting for rust. In an exposed position 202 often stains and pits within a year, but by then the railing is installed. If brown marks have already appeared, see tea staining on stainless steel before assuming the grade is wrong, because 304 can also stain near the coast.

What to write into the purchase order

"Stainless steel railing" on a quotation is not a specification. Put the following in writing:

• The grade by name for every part: tube, handrail, brackets, base plates and fasteners. Hidden parts are where substitution happens.
• The composition limits you expect, for example nickel 8 % minimum for SS 304.
• Mill test certificates for each lot, with heat numbers that match the material marking.
• Your right to have delivered material tested by XRF at a laboratory of your choice.
• What happens if a test fails: replacement at the supplier's cost.

The same wording applies whether the steel is going into a railing or a window grill; how those two differ is in railing vs grill. Buyers importing hardware need the documents even more, since they cannot inspect before shipment; see our guide to exporting stainless steel railing and, for North American deck projects, the glass deck railing hardware guide.

Which grade to ask for

SS 304 is the correct default for railings. SS 202 is acceptable only for dry interior work, and coastal or poolside sites need SS 316, as explained in the SS 304 vs 316 guide. Prince Railing manufactures in SS 304 and SS 316, and the grade is confirmed on the quotation. To see what honest pricing looks like by system, use the price per running foot guide, or send us your requirement.