Does Stainless Steel Turn Skin Green? More Wear, More Risk

Solid 304 or 316 austenitic stainless steel does not turn skin green in ordinary wear. The green mark is a deposit of copper salts, and those two mill grades are specified without copper as an alloying addition: Outokumpu’s Core 304/4301 mill sheet lists a typical 18.1 percent chromium and 8.1 percent nickel with no molybdenum, while its Supra 316/4401 sheet lists 17.2 percent chromium, 10.1 percent nickel, and 2.1 percent molybdenum. A green band appears when a gold electroplate as thin as 0.175 microns of fine gold, the floor in the Federal Trade Commission’s jewelry guides at 16 CFR 23.3, wears through to copper or brass. That chance rises with wet hours, remaining coating thickness, and how often the piece is worn without wiping. Pascale Haudrechy, then at the stainless producer Ugine, with Strasbourg contact-dermatitis clinician Jean Foussereau, Bernard Mantout, and Bernard Baroux, measured nickel release from 304, 316L, and 430 at under 0.03 micrograms per square centimeter per week in synthetic sweat, against about 100 from nickel-plated samples. A stain that washes off is a copper-salt film. An itchy delayed rash at the same site is contact dermatitis.

How does more wear change whether stainless steel turns skin green?

The answer scales with contact time and with how often the same face sits on wet skin. A solid 304 or 316 ring worn dry for an evening is a different object from a plated brass bangle left on through a week of showers.

Haudrechy’s leaching work held coupons in synthetic sweat for one week. Low-sulfur 304, 316L, and 430 stayed under 0.03 micrograms of nickel per square centimeter per week. That week measures nickel. The green stain still needs copper at the contact face. On a gold covering over a copper-containing base, ISO 3160-2’s porosity check runs 24 hours and fails any sample that shows green droplets or green deposits to the naked eye. Those 24 hours belong to a defective coating.

The FTC’s consumer page on buying gold jewelry states that gold plating wears away depending on how the item is worn and on the thickness of the plating. REACH Annex XVII Entry 27, as restated by the Nickel Institute, requires a non-nickel coating over a nickel-releasing article to keep release at or below 0.5 micrograms per square centimeter per week for at least two years of normal use. Two years is the regulatory durability claim for that barrier. A 0.175-micron fashion electroplate is not that barrier.

Amanda Gizzi, jewelry expert and spokesperson for Jewelers of America, told Wirecutter’s Frances Solá-Santiago that plated jewelry, brass or copper under a thin gold or silver layer, is not recommended for summertime wear because it can scratch and tarnish. McKenzie Santimer, a certified gemologist, told the same outlet to rinse a piece after extra sweat or after hours in the ocean or a pool.

The leftover grade is free-machining 303, which Haudrechy and Foussereau found released enough nickel in acid sweat to react in some already-sensitized patients.

What chromium, nickel, and molybdenum percentages are in jewelry stainless steel?

Jewelry-grade stainless is almost always sold as 304 or 316, often 316L. Those numbers are mill grades.

Outokumpu’s Core range datasheet gives typical mass percent for Core 304/4301 (EN 1.4301, UNS S30400, ASTM Type 304) as 0.04 carbon, 18.1 chromium, 8.1 nickel, and no molybdenum. Its Supra 316/4401 page lists 0.04 carbon, 17.2 chromium, 10.1 nickel, 2.1 molybdenum, and 0.04 nitrogen. Outokumpu describes 304 as a classic 18 percent chromium, 8 percent nickel austenitic steel.

The specification ranges are wider, and the editions do not all print the same chromium window for 304. Outokumpu’s Core 304/4301 grade data sheet lists ASTM A240 at 17.5 to 19.5 percent chromium and 8.0 to 10.5 percent nickel, and ASME SA-240 at 18.0 to 20.0 percent chromium with the same nickel band. The British Stainless Steel Association’s composition table lists S30400 at 17.5/19.5 chromium for the A240 plate range and 18.0/20.0 chromium with 8.0/11.0 nickel for A276 bar. Those two chromium floors, 17.5 and 18.0, both circulate as Type 304.

Type 316 is less disputed. ASTM A240, as tabulated by the British Stainless Steel Association and by mill reprints of A240/A240M, sets chromium at 16.0 to 18.0 percent, nickel at 10.0 to 14.0 percent, and molybdenum at 2.00 to 3.00 percent. 304 has no molybdenum requirement.

Copper is the metal that greens skin. It is not a specified alloying addition in 304 or 316. It does appear in other stainless families: Outokumpu’s Core 201/4372 typical row carries copper with 6.6 percent manganese and only 3.6 percent nickel. The FTC’s jewelry guides at 16 CFR 23.11 name austenitic stainless steels among metals that may be considered corrosion resistant, a sentence about rust language in advertising.

What nickel-release rate does stainless steel show next to plated brass?

Nickel content and nickel release are different quantities. 304 typically holds about 8 percent nickel by mass; 316 typically holds about 10 percent.

Regulation (EC) No 1907/2006, REACH Annex XVII Entry 27, sets a migration limit of 0.5 micrograms per square centimeter per week for articles in direct and prolonged skin contact, and 0.2 for post assemblies in pierced skin. EN 1811 is the reference test: one week in artificial sweat. EN 1811:2023, per the Hohenstein bulletin on that revision, treats a result as compliant with the 0.5 limit at or below 0.88 micrograms per square centimeter per week after measurement uncertainty. EN 1811:2011+A1:2015 used a strict less-than 0.88. The 0.88 figure is the same. The inequality is not.

Haudrechy, Foussereau, Mantout, and Baroux’s 1993 Corrosion Science paper and the 1994 Contact Dermatitis follow-up put the same comparison in numbers. In acidic artificial sweat, nickel-plated samples released about 100 micrograms per square centimeter per week. Low-sulfur 304, 316L, and 430 stayed under 0.03. AISI 303 released about 1.5. Patch tests on 50 already nickel-sensitive patients: 96 percent reacted to the nickel-plated samples, 14 percent to 303, none to the low-sulfur nickel-bearing steels. The authors’ line, which Foussereau signed as clinician, was that nickel-containing 304 and 316 steels should not induce contact dermatitis, while 303 should be avoided.

The Copper Development Association specifies cartridge brass C26000 (ASTM B36) at 68.5 to 71.5 percent copper, zinc the remainder. Once a gold film is gone, that copper meets sweat and forms green salts. A nickel underplate under that gold is a separate release path, the one REACH’s 0.5 limit is written to police.

| Property | 304 / 316 stainless | Plated copper or brass | Nickel dermatitis | |---|---|---|---| | Green stain | No specified copper | Yes after plate wears | Not the stain | | Copper | None specified | C26000 68.5–71.5% Cu (CDA) | — | | Nickel in metal | 8.0–10.5% or 10.0–14.0% | Often a nickel underplate | Immune reaction | | Ni release | <0.03 µg/cm²/week (Haudrechy) | ~100 µg/cm²/week if Ni-plated | REACH 0.5 (0.2 piercing) | | Clock | 1-week EN 1811 leach | ISO 3160-2: green in 24 h | Rash 12–48 h |

How thick is the coating that fails, and when does it fail?

Two thicknesses sit on the same finger. Stainless steel protects itself with a chromium-rich oxide a few nanometers thick. Plated fashion jewelry protects a copper alloy with a gold film measured in tenths of a micron.

ASM International’s note on the passive layer in stainless steels puts that chromium oxide/hydroxide film at 1.5 to 2.5 nanometers under normal conditions. A 2019 Scientific Reports TEM study of polished SUS304 measured an amorphous passive film about 3.8 nanometers thick. Those two figures disagree. Both are nanometers. ASTM A967 specifies chemical passivation treatments that rebuild that film after machining; it does not set a jewelry coating thickness.

The FTC’s jewelry guides at 16 CFR 23.3 allow “gold electroplate” from a minimum thickness throughout equivalent to 0.175 microns of fine gold, and “heavy gold electroplate” from 2.5 microns. Gizzi told Wirecutter that some plated pieces carry a PVD layer marketed as waterproof, and that this layer can peel with consistent wear.

Wear duration before a green mark is a coating story. ISO 3160-2’s 24-hour porosity test is the laboratory fail for green deposits on a gold covering over copper. REACH’s two-year clause is the legal durability demand for a nickel-blocking coat. A ring’s inner band spends those microns faster than a pendant. Solid 316 has no copper plate to spend.

Does wet wear or a shower change the stainless steel answer?

Water and sweat change the rate. The alloy stays the same. Solid 304 and 316 do not grow a green copper film because there is no specified copper to dissolve. Wet hours do raise the chance of a green mark on plated copper or brass, and they raise nickel release on a damaged or resulfurized surface.

Human sweat pH is not a single number. Aleksandr B. Stefaniak and Christopher J. Harvey, in their 2006 NIOSH review of skin-surface film liquids, put the median pH of whole-body human sweat at 5.3, with reported values spanning about 2 to 8.2. EN 1811’s artificial sweat is 0.5 percent sodium chloride, 0.1 percent lactic acid, and 0.1 percent urea, brought to pH 6.5 ± 0.05. ISO 3160-2’s watch-covering perspiration is a different liquor at pH 4.7 and 40 °C: 20 g/L sodium chloride, 17.5 g/L ammonium chloride, 5 g/L urea, 2.5 g/L acetic acid, and 15 g/L lactic acid. The three pH figures, 5.3, 6.5, and 4.7, are not interchangeable. Haudrechy showed that 303’s nickel release crossed 0.5 micrograms per square centimeter per week at pH 4.5 and stayed under it at pH 6.6.

Gizzi’s rule is last on, first off: on after sunscreen, off before the shower. Santimer adds a rinse after hours of sweat, ocean, or pool, then flat drying. Jewelers of America tells wearers to wipe jewelry after every wear with a slightly damp cloth, and to have a professional cleaning at least once a year. For pieces worn regularly, Gizzi recommended a weekly deep-clean in dish soap.

A shower on solid 316 is wet service the alloy is specified to survive. A shower on a 0.175-micron gold film over brass is a weekly dose of chloride and surfactant. Jewelers of America tells wearers to keep fine jewelry out of chlorinated and salt water.

For a piece of unknown pedigree:

1. Wipe with a soft cloth after every wear.
2. Deep-clean daily-wear stainless weekly with mild soap; skip stiff bristles on plated pieces.
3. Keep plated copper or brass dry. If a green mark appears, wash the skin and inspect the inner contact face.
4. Treat an itchy delayed rash as a medical question.

How does a green copper mark differ from nickel contact dermatitis?

Green is chemistry. Copper at the surface meets chloride, lactic acid, and water in sweat and forms copper salts that transfer onto skin. ISO 3160-2 treats visible green deposits on a gold covering as a porosity fail.

The rash is immunology. Dermatologist Amanda Oakley, author of DermNet’s nickel-allergy monograph in Hamilton, New Zealand, describes nickel allergy as one of the most common causes of contact allergic dermatitis, with intensely itchy, red, blistered skin at the contact site. On jewelry she writes: “Hypoallergenic stainless steel, solid gold (12 carat or more), and silver jewellery should be safe.” WebMD’s nickel-jewelry page, medically reviewed by Carol DerSarkissian, MD, on 3 May 2026, puts typical onset at 12 to 48 hours after contact. Mayo Clinic’s nickel-allergy page states that an allergic reaction usually begins within a couple of days. Those two clocks overlap. Neither is the 24-hour green-deposit test.

A stain that is gone after soap is not a patch-test result. A delayed itchy plaque that returns each time the same metal is worn is. Haudrechy’s already nickel-sensitive patients did not react to low-sulfur 304 and 316. They did react to nickel plate. Nine-carat gold and white gold, Oakley notes, can contain nickel. The neighbor of the green stain is the underplate.

How can a buyer tell whether jewelry is truly stainless steel?

Look for a 304, 316, or 316L stamp. The word stainless alone is not a grade. 316L is the low-carbon variant used for much body jewelry; its molybdenum band is still 2.00 to 3.00 percent. Ask whether the contact face is solid alloy or plated. The FTC’s gold-electroplate language at 16 CFR 23.3 is the reminder that a gold color can sit on 0.175 microns of metal.

The dimethylglyoxime spot test, described by Oakley on DermNet, turns a cotton bud pink when free nickel is present. It is a release screen, not a grade certificate. Haudrechy warned that DMG can show nickel in the bulk without measuring the dissolution rate that reaches skin.

A magnet can mislead. Annealed austenitic 304 and 316 are generally non-magnetic; cold-worked jewelry wire can attract a magnet anyway. Ferritic 430 is magnetic and, in Haudrechy’s leach, still released under 0.03 micrograms of nickel per square centimeter per week.

If a green mark appears after wet wear, the contact face is behaving like copper. Outokumpu’s 18.1/8.1 or 17.2/10.1/2.1 typicals do not shed that stain. Wash the skin. Inspect the inner band for worn gold, brassy yellow, or a flake of PVD.

FAQ

How can I stop stainless steel from turning my skin green?

Solid 304 or 316 stainless rarely deposits green copper salts. If a mark appears, the contact face is likely plated brass under a worn film. Jewelers of America says to wipe jewelry after every wear. Amanda Gizzi of Jewelers of America told Wirecutter to deep-clean daily-wear pieces weekly and to take jewelry off before the shower.

Which metals do not turn skin green?

Austenitic stainless 304 and 316, titanium, platinum, and high-karat gold without copper at the contact face do not form the green copper salts that stain skin. The FTC’s jewelry guides treat austenitic stainless steel as corrosion resistant. Copper, brass, bronze, and worn gold electroplate over those bases do stain once sweat reaches the copper.

Does stainless steel turn skin green when wet?

Wet hours raise the chance of a green mark on plated copper or brass, because sweat dissolves copper salts. Solid 304 and 316 have no specified copper. Haudrechy’s week-long sweat tests put nickel release from those grades under 0.03 micrograms per square centimeter per week. Water does not turn that steel green.

Can I wear stainless steel in the shower?

Solid 304 or 316 stainless can be worn in the shower; the alloy is specified for wet service. Amanda Gizzi of Jewelers of America still told Wirecutter to take jewelry off before showering, because soaps and leftover sweat film any metal. Plated fashion pieces sold as stainless should stay dry.

How can I tell whether jewelry is truly stainless steel?

Look for a 316, 316L, or 304 stamp and a seller who will name the grade. A magnet is a weak test: annealed austenitic steel is usually non-magnetic, but cold-worked jewelry can attract one. Dimethylglyoxime flags releasable nickel, not mill grade. A green stain after wet wear points to copper at the surface.

Is a green mark different from an itchy rash?

Yes. Green is a copper-salt stain that washes off. An itchy, delayed rash at the contact site is allergic contact dermatitis, most often to nickel, as dermatologist Amanda Oakley describes on DermNet. WebMD’s page reviewed by Carol DerSarkissian, MD, puts typical onset at 12 to 48 hours. The stain is chemistry; the rash is immune.