Rhodium (Rh): Properties, Hardness, and Applications

The silver-white, hard precious metal material rhodium (Rh) belongs to the light platinum metals (density around 12 g/cm³). Rh is resistant to acids in a compact form such as iridium, but it dissolves finely distributed in aqua regia and concentrated sulfuric acid. It reacts with oxygen at high surface temperature (in contrast, ruthenium and osmium form volatile oxides). The processability depends crucially on the degree of purity. Pure rhodium can be forged in red hot, can be rolled and pulled. The material is characterized by high thermal and electrical conductivity. Application: Rhodium has greater practical importance than the other platinum metals except platinum and palladium. In car exhaust catalysts, mainly Pt / Rh or Pt / Pd are used. Furthermore, rhodium is used in chemical and electrochemical apparatus engineering (crucible for growing single crystals for the optical industry and laser technology), for spinnerets and thermocouples (Pt / Rh). Rhodium layers have the advantage over all other platinum metal coatings of particularly high hardness, mechanical and chemical resistance and high reflectivity (for example, for silvering). Furthermore, Rh is also used as a contact material and for heating coils and mirrors. Rhodium is sufficiently ductile, corrosion resistant, oxidation resistant up to 800°C, abrasion resistant. It is limited machinable, electrodepositable and can be separated from the gas phase.

Properties

General

Mechanical

Thermal

Electrical

Chemical properties