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Most of this site is made in one grade, so it is worth being precise about what that grade is. 316L is the molybdenum-bearing austenitic stainless steel: the one specified for surgical implants and marine fittings, and the one that stays bright in a shower, on a wrist, and in a coastal warehouse. It is also the grade most often mislabelled, because the difference between 316L, 304 and 201 is invisible in a photograph and worth real money per tonne.
What 316L actually is
| Property | 316L stainless steel |
|---|---|
| Standard designation | 316L (AISI/ASTM); SUS316L under JIS; 1.4404 under EN |
| Family | Austenitic stainless steel |
| Chromium | 16–18% — forms the passive oxide layer that resists corrosion |
| Nickel | 10–14% — the austenite stabiliser, and the reason it is not nickel-free |
| Molybdenum | 2–3% — the element that gives it its chloride resistance |
| Carbon | 0.03% max — the “L” in 316L; lower carbon, less sensitisation at welds |
| Magnetism | Weakly magnetic or not magnetic in the annealed state |
| Specified for | Surgical implants (ASTM F138), marine fittings, food equipment — and stainless jewellery |
The “L” matters more than people expect. Low carbon (≤0.03%) means the steel does not sensitise around welds, which is why chain links and hollow forms hold up rather than corroding from the inside at the join. The molybdenum content is the other half of the story: it is what resists chlorides, and chlorides are what rust cheap stainless jewellery.
316L against 304 and 201
| 316L | 304 | 201 | |
|---|---|---|---|
| Molybdenum | 2–3% | None | None |
| Chloride and pitting resistance | Highest of the three | Moderate | Lowest |
| Nickel | 10–14% | 8–10.5% | 1–4%, usually with manganese |
| Steel cost | Highest | Middle | Lowest |
| Where you meet it | Marine fittings, implants, better jewellery | Kitchenware and cheaper jewellery | The cheapest imported jewellery and watch bands |
| What it does to your returns | Tarnish and rust complaints stay low | Fine in a dry climate, worse on a coast | The usual source of “my necklace went rusty” |
What “surgical steel” means — and what it does not
“Surgical steel” on its own is a marketing term, not a specification. There is no standard that defines it, so a supplier can print it on 316L, on 304, or on 201, and no one is technically lying. What the phrase usually gestures at is 316L — the grade that ASTM F138 specifies for implant applications — so when you see it, the useful next question is not “is it surgical?” but “which grade, and can you put that in writing?”
We name the grade rather than the adjective, which is why this page says 316L (SUS316L under the Japanese standard) everywhere a supplier might write “surgical steel”.
How to check a shipment
None of these replaces the other, and the cheap ones are screening checks rather than proof:
- Ask for the mill test report — the MTR (also called a mill test certificate, MTC) states the heat chemistry and is the only document that actually says what the steel is.
- Try a magnet — 316L is weakly magnetic or non-magnetic in the annealed state. Strong attraction suggests a ferritic steel, or 201. Treat it as a screen, not a verdict.
- Weigh it — 316L is denser in the hand than the cheaper substitutes, and hollow forms that should be solid give themselves away.
- Have it read — a handheld XRF analyser reports chromium, nickel and molybdenum in seconds. For a first large order this is the cheapest insurance there is.
- Look at the finish — burrs, rough solder at the joins and uneven plating cause more returns than the alloy ever does.
We state the grade on every design page. If your market needs documentation, tell us and we will confirm what is available on that design before you order — we would rather confirm it than assume it.
Skin, nickel and compliance
316L is hypoallergenic for most wearers, and it is not nickel-free. It contains 10–14% nickel by specification, so a page that claims both “316L” and “nickel-free” is contradicting itself. For a customer with a known nickel sensitivity, the honest position is that 316L usually behaves well because nickel is bound in the alloy and releases slowly — not that there is no nickel present.
- EU — the Nickel Directive, carried into REACH, limits nickel release from items in prolonged skin contact to 0.5 µg/cm²/week. That is a requirement on release, not on content.
- US — CPSIA applies to children’s products; California Proposition 65 requires a warning where listed substances exceed the thresholds.
- Biocompatibility — ISO 10993 is the family of standards used where a material is assessed for contact with the body.
These are the standards your market will ask about, and they are why testing is a line item rather than an adjective. If you need a nickel-release test for a specific destination, quote it as its own line and we will tell you what we can and cannot arrange.
PVD, ion plating and electroplating
Two gold tones are sold on the same steel, and they are not the same product. Electroplating deposits gold from a tank; PVD (also sold as ion plating) bonds the coating in a vacuum chamber and is harder and more abrasion-resistant. Both are quoted per micron, and both eventually wear where they rub. Because the base underneath is stainless, wear shows as a change of colour rather than as rust — which is the practical argument for putting the plating on steel rather than on brass.
The wording to put in a purchase order, and how to compare two quotes, is on the plating and finishes page.
Care that keeps it right
- Warm water, mild soap and a soft cloth. Stainless does not need polish.
- Rinse after a pool or the sea. Chlorine and salt are what attack the passive layer.
- Skip chlorine bleach, and skip ultrasonic cleaners on anything plated.
- Store dry and separately — scratches, not tarnish, are what a stainless piece suffers from.