Rhodium Plating

Definition - What does Rhodium Plating mean?

Rhodium plating is a metal deposition process used to coat materials with a decorative and protective layer of rhodium.

Rhodium is a noble metal that imparts an exceptionally bright and hard-wearing finish when applied as plating. When applied as a thin plate, it affords a robust finish of exceptional brightness. Rhodium finishes can greatly increase the appearance and durability of any metal to which they are applied.

Rhodium plating is used on white gold and sterling silver jewelry as a means of creating a highly durable, tarnish-resistant surface.

Corrosionpedia explains Rhodium Plating

Rhodium is electroplated on white gold and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewelry business. It may also be used in coating sterling silver to protect against tarnish, which is silver sulfide (Ag2S) produced from the atmospheric hydrogen sulfide (H2S).

All phases of rhodium plating are interconnected and each must be executed correctly if best results are to be obtained. Rhodium plating solutions are very sensitive to contamination by errant base metals. Rhodium plating operations should be completed in an enclosed, clean area with adequate ventilation.

The most common method of rhodium plating is done by electroplating process. This encompasses submerging the recipient material in a heated bath of rhodium-based plating solution and running an electric current through the bath, using the recipient as a cathode or negative electrode. This process deposits rhodium from the solution to permanently bond to the recipient surface. Plating solutions usually consist of:

  • Rhodium sulfate
  • Sulfuric acid
  • Water

Rhodium plating is done in a similar way to silver plating or galvanizing. The thickness of the rhodium-plated surface layer is measured in microns.

Rhodium plating's lifespan depends upon a number of factors:

  • Amount of wear the jewelery receives
  • Original thickness of the plating
  • Individual body chemistry
  • Quality of the plating
  • Color of the underlying gold

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