Surface treatments encompass all techniques aimed at enhancing the properties of a component’s surface (reducing friction coefficients, protecting against corrosion, etc.) and/or improving its aesthetics. In watchmaking, surface treatments can apply to both the exterior (case, dial, hands) and the movement.
Traditionally, galvanic processes are the most widespread in the watchmaking world. To galvanically treat a component, a thin layer of another metal (usually gold or rhodium) is deposited on its surface through electrolysis. The base material of the component must conduct electricity to be eligible for galvanic treatment.
Gilding is a galvanic process that aims to cover the surface of the component with a thin layer of gold. All shades of gold can be applied using this process. According to Swiss regulations, a component must be covered with a minimum thickness of 5 microns (0.005mm) of gold higher than 585/1000 (14K) to be labelled as “gold-plated”.
The principle of rhodium plating is similar to gilding. It involves applying a thin layer of rhodium to the surface of the components using a galvanic process. In 2023, rhodium was considered as the most expensive metal, far ahead of iridium, gold, or platinum. Rhodium is highly valued for its vibrant white colour, and it is an excellent electrical conductor.
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