Technique → Surface treatments

GALVANIC TREATMENTS

Galvanic treatments involve coating the surface of a metal (the substrate) with a thin layer of another metal using an electrolytic process. The substrate is immersed in a bath containing suspended molecules of the metal intended to cover the substrate’s surface. By passing an electric current between an immersed anode and the object to be treated (cathode), which must be conductive, the suspended molecules deposit onto the substrate’s surface. Depending on the duration of the process and the intensity of the current, the thickness of the applied layer can be controlled.

This operation serves to protect the substrate from oxidation and to alter its colour. Historically and predominantly used in watchmaking are yellow gold, rose gold, and rhodium (white gold), which are all resistant to corrosion. Nowadays, numerous other metals or metal combinations expand the range of possible colours (such as ruthenium, black gold, etc.).

It was the Italian physicist Luigi Galvani who discovered in 1780 that it was possible to protect a metal from corrosion by applying a thin layer of zinc to it. The various electrolytic techniques owe their names to him. The process found applications in goldsmithing, and then in watchmaking from the mid-19th century onwards, and remains widely used today, although other technologies (CVD, PVD) began to develop towards the end of the 20th century. While gold and rhodium have historically been used in watchmaking and remain the most commonly encountered treatments, other metals or combinations of metals (such as ruthenium, black gold, etc.) have supplemented the palette of possible colours since the second half of the 20th century.

Advantages:

  • Provides long-lasting protection against oxidation for the substrate
  • Allows for modification of the substrate’s colour
  • Produces a vibrant and uniform colour

Disadvantages:

  • Can only be applied to materials that conduct electricity
  • Limited colour palette
  • Electroplating baths can be toxic and environmentally polluting