A practical guide for makers, jewelers, and EDC craftspeople — Awesome Metals
Most people meet zirconium in a chemistry classroom or inside a nuclear plant. But over the last decade, Zirconium 702 has quietly become one of the most interesting metals on a jeweler’s bench: hypoallergenic, corrosion-proof, and capable of turning a deep, permanent black that no coating can match. This guide covers what Zr702 actually is, how it compares to titanium, and what to know before you buy or machine it .
1. What Is Zirconium 702?
Zirconium 702 (UNS R60702, ASTM B551) is the commercially pure zirconium grade —
“commercially pure” meaning unalloyed zirconium with tightly controlled impurity limits, not a laboratory-pure element. It is the workhorse grade of the zirconium world: maximum ductility, maximum corrosion resistance, and moderate strength. Its close sibling, Zirconium 705 (UNSR60705), adds about 2–3% niobium for higher strength at some cost in ductility.
2. Chemical Composition (ASTM B551, Zr702)
3. Key Mechanical and Physical Properties
4. Black Zirconium: A Grown Finish, Not a Coating
Here is the part jewelers care about most. Like titanium, zirconium forms a thin oxide film when heated, and that film produces interference colors — blues, purples, golds. Taken further, a controlled high-temperature oxidation grows a hard, black zirconium-oxide layer. This is what the industry calls “black zirconium.”
The important distinction: the black is grown out of the metal itself, not sprayed or plated on. Leading makers of black zirconium jewelry describe it as a hard oxide layer, much harder than the raw metal and far more durable than black PVD coatings or black tungsten finishes, which can rub through at the edges.
An honest caveat: the black layer is thin. It will not fade or rub off in normal wear, but a deep scratch can reveal the silver-grey metal underneath. For most wearers that is a non-issue; for a maker it is simply something to disclose.
Compared with heat-colored rainbow films on titanium (tens of nanometers, fragile), a properly grown black zirconium oxide is in a different league of wear resistance — which is why black Zr702 has become a staple for men’s wedding bands.
5. Zr702 vs. Grade 5 Titanium
6. Typical Applications
cladding, heat exchangers, valves — the original home of zirconium.Nuclear and chemical processing:
implants and surgical tools (biocompatibility).Medical:
black zirconium rings and wedding bands, beads, pen and knife components. The black
finish plus hypoallergenic skin contact is the combination that sells it.Jewelry and EDC:
7. Working Zr702: Notes for Makers
use sharp tooling, moderate speeds, and plenty of coolant. Like titanium it can work-
harden, so avoid dwelling and keep feeds consistent.Machines much like titanium:
good ductility makes it friendly for damascus-style layer stacking and twisting with
titanium alloys.Forging and twisting:
polishes to a bright silver-grey; bead-blasting gives an even satin base before
blackening.Finishing:
a controlled high-temperature oxidation. Process parameters are the maker’s own know-
how — expect to dial them in on scrap first.Blackening:
We stock Zr702 round bars at titaniumalloy.us — every batch traceable, cut to order in Charlotte, NC. Questions about working it? Contact us; we make with the same stock we sell.