Anything without free iron in it, which covers titanium, platinum, pure gold and, in normal wear, S316L Surgical Steel. Strictly speaking most jewelry can't rust at all, because rust is iron oxide and there's no iron in gold, silver or titanium. What people call rust on an earring is nearly always tarnish or corrosion instead, and those have different causes and different meanings. Our materials page names what we use and how each behaves.
Knowing which of the three you're looking at tells you a lot about what the earring is made of.
Rust, tarnish and corrosion are not the same thing
Rust is iron oxide. It needs iron, oxygen and moisture. It's orange brown, it flakes, and it eats into the metal rather than sitting on it. If an earring genuinely rusts, it contains unprotected iron, which means it's a cheap plated steel with the coating gone.
Tarnish is a surface reaction. Silver reacts with sulfur compounds in air and on skin to form silver sulfide, which is the black film on sterling. Copper does something similar. Tarnish sits on top, doesn't consume the item, and polishes off.
Corrosion is the general case. Any metal degrading through reaction with its environment. Stainless steel resists it because chromium forms a passive oxide layer that reforms whenever it's damaged. That's what stainless means, and it's a resistance rather than an immunity.
Which materials stay clean
Titanium. Forms its own tough oxide layer instantly. No iron, so no rust, and it doesn't tarnish.
Platinum. Very unreactive. Develops a soft surface patina over years rather than tarnishing.
24 karat gold. Pure gold doesn't oxidize at all. Nothing to tarnish, nothing to rust.
S316L Surgical Steel. Contains iron, so it can in principle corrode, but the chromium and molybdenum make it very resistant. In normal wear, including swimming and showering, it stays clean. Rinsing after pool water helps the passive layer do its job.
Which ones discolor, and what it means
Sterling silver tarnishes. Expected behavior, not a fault. It polishes off and comes back.
Low karat gold dulls. The gold doesn't react. The 25% or 42% that isn't gold does, particularly the copper.
Rose gold marks skin. Its color comes from a high copper content, and copper corroding against skin is what produces the green.
Plated jewelry does something more confusing. The coating doesn't tarnish, so it looks fine, right up until it wears through in one small spot at the post. Then the base metal underneath starts corroding and you get a dark patch on a piece that's otherwise perfect. Most "my earrings are rusting" photographs are this.
Brass and nickel silver corrode readily. Copper based, both of them, and both stain skin.
What discoloration is telling you
Orange brown flakes. Iron. Cheap plated steel with the plating gone. Take it out.
Black film that polishes off. Tarnish, most likely silver or a silver alloy.
Green marks on skin. Copper corroding. It's the alloy content doing it, not dirt.
A dark patch at the post only. Plating has worn through at the highest friction point. The front will still look new.
Dull gray with no film. Usually surface deposits from soap or hard water rather than a metal reaction, and it washes off.
If the ear itself is red, hot, swollen or discharging rather than just marked, that's not a metal question and it's one for your pediatrician.
Why the post is the place to look
Every one of these processes starts where contact is closest and friction is highest, which is the post inside the piercing channel and the butterfly back behind the lobe.
That's the opposite of where anyone looks. The front is designed to be seen and it's the part that stays presentable longest. A pair can be well past the point where the coating has gone and still photograph perfectly.
Take a pair she wears daily, turn it over, and compare the shade of the post with the shade of the front. If they've diverged, the coating has.
What we do
purepixxi uses two materials, and neither will rust in normal wear.
S316L Surgical Steel throughout our Polished Surgical Steel range. One alloy, front, post and butterfly back, with nothing plated over it. There's no coating to wear through, so there's no moment at which a different metal starts contacting skin. It won't tarnish and, in daily wear including swimming, it won't corrode.
24K Pure Gold, which is pure 24 karat gold applied onto a solid S316L Surgical Steel core with Aunix™ 24K, our engineered gold finish. Pure gold doesn't oxidize, so the surface stays as it is. It's a gold-plating process and we say so, which means the finish is a surface with a finite life. When it eventually wears at the post, what's underneath is the same S316L we sell on its own, not brass and not a nickel barrier layer.
We don't use rose gold, because the color is copper. We don't use brass or nickel silver at all.
Independently tested by SGS to ASTM F2923, CPSIA and BSEN 71-3, with nickel release not detected under EN 1811. Report BTO 341803/1, and I'll send it if you ask.
You can see the range on the Polished Surgical Steel collection.
The easiest pair to keep clean is the one with the fewest places for anything to gather, which is why we make the 5mm Star Stud Earrings in Surgical Steel.
Questions parents ask next
Can stainless steel rust? It can corrode under harsh conditions, and low grades pit in salt water. S316L in daily wear, including pools, stays clean.
Why do her earrings go black? Usually tarnish if they're silver, or a worn coating exposing base metal if they're plated. Occasionally it's abrasion from products on the skin rather than the metal at all.
Does gold plated jewelry rust? The gold doesn't. What's under it can, once the plating wears through, and that's what people are seeing.
Can I clean rust off an earring? You can remove the deposit, but the plating is already gone at that point, so the same thing returns. It's a signal to retire the pair rather than restore it.
Does 316L stay clean in a swimming pool? Yes. Rinse in fresh water afterwards so chlorides aren't left sitting on the surface, and dry it properly.
Related reading
- Do gold earrings tarnish?
- Why do earrings turn ears black?
- Surgical steel vs stainless steel: what's the difference?
- How long does gold plating last on earrings?
About the author. Matt Westmore is the founder of purepixxi. He came to children's jewelry from manufacturing and sourcing rather than marketing, which means he has walked the factory floors and knows what is actually inside a product rather than what a label says about it. purepixxi uses two materials only, names them exactly, and has them independently tested.
