Rhodium (Plating)
Pure rhodium, applied as electroplate
Extremely bright, mirror-white, the whitest and most reflective of all metals. Creates the characteristic 'high polish' look of plated white gold
Composition
Pure rhodium, one of the rarest elements in the platinum group
Physical properties
| Density | 12.41 g/cm³ | Weight per unit volume. Platinum is ~40% heavier than 18k gold at equal size |
|---|---|---|
| Melting range | 1964 °C | Working temperature for alloys. Pure metals have a sharp melting point |
| Vickers hardness | 800 HV | Higher HV = greater scratch resistance in service |
| Mohs hardness | 6 | Approximate equivalent for comparative reference |
| Tensile strength | 970 MPa | Resistance to breaking under tension, relevant for prongs and fine settings |
| Purity | 99.99% | Fine metal content by mass |
| Tarnish resistance | Excellent | Surface oxidation / sulphidation under typical wear conditions |
| Workability | Poor | Ease of forming, soldering, and fabricating under standard jewellery workshop conditions |
| Hypoallergenic | Hypoallergenic | Likelihood of triggering skin reactions under normal wear |
Common uses
Plating on white gold (0.5–2 microns), plating on sterling silver for tarnish resistance, high-reflectivity mirror coatings, catalytic converters
Hallmarking & identification
Not hallmarked as a finished metal; it is applied as a surface treatment. Extremely expensive by weight but used in microscopic quantities. Cannot be worked or fabricated in bulk.
Rhodium plating on white gold wears through with time (typically 1–3 years for rings, longer for earrings and pendants). Signs of wear: yellowish areas reappear. Replating is routine and inexpensive. Avoid abrasives and ultrasonic cleaning which accelerate wear.
Market & pricing
One of the most expensive metals by weight, orders of magnitude above platinum. Negligible cost per piece due to the tiny quantities used (microns of thickness).