What Is Rhodium Plating?
In rhodium plating, a thin film of rhodium is formed on the surface of the material by placing the material in a liquid in which rhodium is molten and passing electricity through it. This film is called rhodium* plating**.
* Rhodium is a member of the platinum group, an expensive metal classified as a precious metal with the element symbol Rh.
** Plating is a technique used to apply a thin film to the surface of a material to protect it.
Rhodium plating is used in various industrial fields such as optical and electronic equipment because it is chemically very stable, has very high hardness, is scratch resistant, has good abrasion resistance, and does not oxidize at temperatures below 500°C. Rhodium plating is used in various industrial fields such as optical and electronic equipment.
It is also used for high-end ornaments, taking advantage of its white luster and high reflectance of 80% or more, which gives it an elegant appearance.
Uses of Rhodium Plating
In industrial applications, rhodium plating is used for electrical contacts (reed switches, etc.) due to its excellent corrosion and wear resistance and low electrical resistance. It is also often used in industrial parts such as mirrors and other optical elements and catalysts to control exhaust gases, taking advantage of its high reflectivity over a wide range of wavelengths.
Materials that can be plated include copper, copper alloys, iron, and stainless steel.
In addition to industrial applications, rhodium plating is also used for high-end decorative items such as eyeglass frames, necklaces, watches, and rings.
Principle of Rhodium Plating
Rhodium is extremely hard and, unlike gold and other metals, cannot be formed into shapes. For this reason, it is often used for plating. It is a platinum metallic element that is chemically stable and does not corrode in ordinary acids or alkalis, and its hardness is about the same as industrial chromium. For this reason, it is also used for industrial applications such as optical equipment.
Rhodium plating has high hardness and excellent wear resistance and does not tarnish at temperatures below 500℃. It also has high light reflectivity and low electrical resistance of only a few microhms, making it suitable for use in areas where antistatic measures are required.
Since it is an expensive precious metal that can cost more than gold, a base coat is usually applied to form a thin rhodium layer of about 0.05~0.3 μm only on the topmost surface layer. Although the film thickness is considerably thinner than normal plating, it functions well as plating even with a thin film thickness because of its good chemical properties, scratch resistance, and hardness.