Rhodium plating is a thin layer of rhodium metal applied to jewelry by electroplating. It makes white gold look brighter and whiter, keeps silver from tarnishing and gives a uniform finish. The plating wears away over time, especially on rings, so jewelers replate pieces as needed.
What rhodium is
Rhodium is one of the six platinum-group metals and one of the noble metals. William Hyde Wollaston discovered it in 1804 in platinum ore, naming it after the Greek word for rose because of the pink color of its salts. The metal itself is silvery white.
Rhodium is very hard, very reflective and highly resistant to corrosion and tarnish. It melts at about 1,964 °C. It is also one of the rarest metals in the Earth's crust and is usually mined as a byproduct of platinum and nickel mining. Its largest use is in catalytic converters for vehicles.
Solid rhodium is hard and brittle, which makes it very difficult to work into jewelry. Instead, jewelers use it as a coating over other metals.
Why jewelry is plated with rhodium
Plating with rhodium does several things:
- It brightens white gold. White gold alloys have a faint yellow or gray tint. Rhodium hides that tint behind a bright, cool white surface.
- It protects silver. Rhodium-plated sterling silver does not tarnish until the plating wears through.
- It gives a uniform color. Plating covers solder seams and small color differences between parts of a piece.
- It adds a hard surface. Rhodium is harder than gold and silver, so it resists light scratches.
Rhodium plating also covers other metals for a white look, such as yellow gold prongs on some rings or base metal in fashion jewelry. Platinum is sometimes plated for extra brightness, though platinum does not need it.
How rhodium plating works
Rhodium is applied by electroplating, a process that uses electric current to deposit metal from a solution onto a surface. The usual steps are:
- The jeweler polishes the piece to a smooth, bright finish, since plating shows every scratch underneath.
- The piece is cleaned with ultrasonic and steam cleaners and an electrocleaning bath to remove oils and polishing compound.
- The piece is rinsed and dipped in a rhodium solution, usually rhodium sulfate or phosphate. A current flows through the bath, and rhodium deposits on the jewelry.
- The piece is rinsed and dried.
The plating is very thin, usually around 0.1 to 1 micron, and often near the low end of that range on standard jewelry. A thicker layer lasts longer but costs more and can crack if too thick, because rhodium is brittle. The whole process takes a short time once the piece is cleaned, though shops often take a few days because of scheduling and checks.
Some gemstones cannot handle the cleaning and plating steps. Porous gems, treated stones, pearls, opal and emerald may be damaged by heat, steam or plating chemicals. Jewelers may need to remove those stones, mask them with a protective lacquer or skip plating. The gemstone treatments page explains why treated stones need extra care.
Wear and replating
Rhodium plating wears away through friction. How fast it wears depends on several factors:
- Where it is worn. Rings wear fastest because hands touch many surfaces. Earrings and pendants can keep plating for years.
- How thick the plating is.
- The wearer's habits. Typing, gardening, gym work and handling hard objects all speed wear.
- The chemistry of skin, lotions and household chemicals.
On a white gold ring, plating usually wears first on the palm side of the band and on raised edges. You may notice a slightly yellowish or gray tone where the white gold alloy shows through. Many jewelers suggest replating rings every 12 to 24 months, though some people go longer.
Replating repeats the process above. The jeweler often checks prongs and stone security at the same time, since the piece is already being cleaned and inspected. Frequent polishing before each replating removes a small amount of metal, which over many years can thin delicate parts.
Black rhodium
Black rhodium is a dark gray to black plating made from rhodium with additives or with a related metal such as ruthenium. It gives jewelry a dark gunmetal finish. Jewelers use it for contrast, such as darkening the settings around white diamonds, setting off colored stones or giving men's jewelry a darker look.
Black rhodium wears in the same way as standard rhodium, revealing the metal beneath. Jewelers often apply it to recessed areas, where it is protected from friction, and leave raised areas bright. Replating black rhodium may require masking parts of the piece.
Rhodium versus other finishes
| Finish | Color | Main purpose | Durability |
|---|---|---|---|
| Rhodium plating | Bright white | Brighten white gold, protect silver | Wears on rings in months to a few years |
| Black rhodium | Gray to black | Contrast and dark finish | Similar to standard rhodium |
| Palladium plating | Gray-white | Nickel barrier on some pieces | Similar thin layer |
| Gold plating | Yellow, rose | Color on silver or base metal | Varies with thickness |
Rhodium plating and allergies
A rhodium plating creates a barrier between the skin and the metal underneath. It can help people with a nickel allergy wear nickel white gold for a while. Once the plating wears through, the alloy is exposed again, and the wearer may react. Palladium white gold, platinum or titanium are more reliable choices for long-term wear by sensitive people.
Caring for rhodium-plated jewelry
Clean rhodium-plated pieces gently with warm water, mild soap and a soft cloth or brush. Avoid abrasive polishes and polishing cloths impregnated with compounds, since they can strip the plating. Remove rings before rough work, sports or handling chemicals. The jewelry cleaning guide covers gem-safe methods.
Frequently asked questions
How long does rhodium plating last?
It varies widely. On rings, plating may last from a few months to around two years. On earrings and pendants it often lasts much longer.
Is rhodium plating bad for jewelry?
No. The plating is harmless to the metal underneath. The main downside is upkeep, since it must be redone as it wears off.
Can silver be rhodium plated?
Yes. Rhodium-plated sterling silver is common in commercial jewelry because the plating prevents tarnish until it wears through.
What is black rhodium?
Black rhodium is a dark plating made from rhodium with additives or a related metal such as ruthenium. It gives jewelry a dark gray to black finish.