Cobalt chrome or titanium: which makes the better wedding ring?

What is a cobalt chrome ring?

A band made from an alloy of cobalt and chromium, not from pure cobalt. The best documented recipe is the alloy standardised as ASTM F75: one alloy maker's data sheet lists it as mostly cobalt with 27 to 30% chromium, 5 to 7% molybdenum and no more than 0.5% nickel. It is the alloy used for knee implants, hip joints and dental prosthetics.

One American seller describes its own cobalt rings as that same medical and dental grade. Recipes vary from maker to maker, so every figure in this guide is for that documented alloy.

We do not make cobalt chrome rings: our contemporary bands are titanium and black zirconium. What follows sets the two metals side by side as fairly as the published sources allow.

Is titanium good for a wedding ring?: Weight, scratches, skin and which grade of titanium is used.

Titanium: The metal itself: density, hardness and what it is good for.

Is cobalt chrome whiter than titanium?

Yes. The jewellers who sell cobalt chrome describe it as naturally white: one large retailer uses those words for its cobalt bands and another seller says the colour closely resembles white gold. That second seller calls titanium silver grey, which is how our own titanium rings look: a cool, soft grey.

So if the aim is a band that could pass for white gold, cobalt chrome comes closer. If you would rather have a quieter grey that looks like what it is, titanium is the one. The ring try-on shows our titanium bands on a photo of your own hand.

Ring try-on: See a titanium band on a photo of your own hand, free.

Platinum line, titanium: A third route to white: a line of solid platinum 950 set into satin titanium.

Satin, polished or hammered?: How each finish looks and how each one wears.

Is cobalt heavier than titanium?

Yes, a little under twice as heavy. The cobalt chromium alloy has a density of about 8.3 grams per cubic centimetre on its makers' data sheets, against 4.5 for titanium. Worked through the same formula our ring weight estimator uses, a 6mm band in size N comes to about 4.1g in cobalt chrome and 2.2g in titanium.

That puts cobalt chrome between black zirconium (3.2g for the same band) and 9ct gold (about 5.6g): a ring you can feel on the hand without the full weight of gold. Titanium is for the opposite taste. It is the ring people forget they are wearing.

Ring weight estimator: Grams by metal, width and size, with the formula shown.

Lightest metal for a wedding ring: Every metal by weight, in grams.

Does cobalt chrome scratch more easily than titanium?

No. Cobalt chrome is the harder metal, so it should mark less easily. One maker's data sheet for an F75 alloy gives about 25 to 39 on the Rockwell C scale, depending on heat treatment. A titanium producer gives its Grade 2, the grade most of our rings are made in, about 80 on the Rockwell B scale. The C scale is the one used for materials harder than 100 on the B scale, so the gap is real.

Those are Rockwell figures, not Mohs. We have not found a properly sourced Mohs number for cobalt chrome, so we do not give one.

Neither ring is scratch proof: one seller of cobalt rings says its own will show scratches in time. Titanium, at about Mohs 6, picks up fine marks that show least on a satin or hammered finish. If scratches matter most to you, black zirconium has the hardest surface we make, at about Mohs 8.

The most durable wedding ring metal: Every metal we make rings in, ranked for scratches and for wear.

Is black zirconium good for a wedding ring?: How the black surface is grown and how it wears.

Are cobalt rings hypoallergenic?

Not for everyone. Both sellers quoted above call cobalt chrome hypoallergenic and the alloy does hold very little nickel. But the ring is mostly cobalt and cobalt is itself a known contact allergen. The NHS lists metals such as nickel or cobalt in jewellery among the common causes of allergic contact dermatitis. The British Association of Dermatologists names the same two metals.

That does not make a reaction likely. DermNet, the dermatology reference, puts cobalt allergy at about 2% of the general population, so most people are not allergic to cobalt. It also notes that cobalt allergy can coexist with nickel allergy. We found no dermatology source that measures how much cobalt a finished cobalt chrome ring releases onto skin, so we will not put a number on the risk. A 2014 study in the journal Contact Dermatitis did find that five alloys used by dental technicians, whose casting alloys are cobalt chromium, all released some cobalt into artificial sweat.

Titanium avoids the question. Most of our titanium rings are Grade 2, which is commercially pure, unalloyed titanium, so there is no cobalt or nickel in the recipe. If you know you react to cobalt, choose titanium or zirconium. If any ring gives you a rash, stop wearing it and see your GP: patch testing is how the exact cause is found.

Metal allergies and hypoallergenic rings: Which ring metals suit sensitive skin and how patch testing works.

Titanium rings: Every titanium ring in the range, made to order in your size.

Can cobalt rings be resized or cut off in an emergency?

Cut off, yes. Resized, usually not. The MSD Manual for clinicians groups cobalt with steel and titanium as hard ring materials and gives one instruction for all three: use a powered ring-cutting saw if one is available or a bolt cutter if not. It reserves breaking a ring apart with locking pliers for hard but brittle materials such as ceramic and tungsten. So a cobalt chrome ring comes off the way a titanium ring does.

Resizing is less settled, because sellers disagree. A jewellery insurer in the United States lists cobalt with titanium, tungsten carbide and stainless steel as metals that cannot be resized, because they are prone to breaking or difficult to work. One large retailer states on its cobalt ring page that the ring cannot be resized. Another seller says a jeweller can resize its cobalt rings. So treat the size you order as the size the ring stays, unless the seller of that ring says otherwise.

Titanium is not cut and rejoined like gold either, but the inside of a titanium band can often be machined to make it slightly bigger, never smaller.

Can a titanium ring be cut off?: Which cutters go through titanium, with what UK hospitals have published.

Why some rings cannot be resized: Which metals can be made larger or smaller and by how much.

Ring size finder: Measure at home in about two minutes, before you order.

Cobalt chrome or titanium wedding band: which is better for hands-on work?

Titanium, for most working hands. Cobalt chrome has the harder surface, so it should show fewer marks. Titanium answers with a little over half the weight, no cobalt or nickel against the skin and a size that can often be eased slightly larger if your hands change.

Whichever you choose, pick a plain band in a satin or hammered finish, so the marks do not show. No ring metal makes a ring safe around machinery: the danger is the ring being caught, not the ring breaking, so either one comes off for work that could catch it.

Choose cobalt chrome if you want the whitest colour, some heft and the harder surface and your skin has never reacted to metal. Choose titanium if you want the lightest ring, the surer answer for sensitive skin and a little room on size.

Wedding rings for hands-on jobs: The right ring for manual work, nursing and the gym and when to take it off.

Plain titanium: A plain titanium band in 4 to 10mm, satin or polished.

Metal chooser: A few questions about your hands, your work and your skin, then a straight recommendation.