Rhodium
An extremely rare platinum group metal used primarily as a catalytic coating in automotive three-way catalytic converters.
Overview
Rhodium is one of the rarest and most valuable metals on Earth, belonging to the platinum group metals (PGMs). In automotive applications it is indispensable as a catalyst in three-way catalytic converters, where it reduces nitrogen oxide (NOx) emissions into harmless nitrogen and oxygen. A typical petrol catalytic converter contains approximately 0.5–2 grams of rhodium alongside platinum and palladium. Despite its tiny quantities per vehicle, rhodium's extreme scarcity — global annual supply is only around 30 tonnes — means it commands extraordinary prices, frequently exceeding $10,000 per troy ounce. This makes it one of the most significant cost drivers in emissions control system procurement. Rhodium is also used as a hardening agent in platinum and palladium alloys, in electrical contact plating, and as a reflective coating in optical instruments. Its high reflectivity and corrosion resistance make it suitable for specialist mirror and jewellery applications. Primary production is a byproduct of nickel and platinum mining, with South Africa accounting for approximately 80% of global supply — creating significant concentration risk for automotive procurement teams.
Automotive Applications
Similar Materials
Palladium
Platinum Group Metal (PGM)
A platinum group metal widely used in petrol engine catalytic converters to oxidise hydrocarbons and carbon monoxide into less harmful emissions.
Platinum
Platinum Group Metal (PGM)
A rare, dense precious metal used as a primary catalyst in automotive catalytic converters to oxidise hydrocarbons and carbon monoxide into less harmful emissions.
Steel
Carbon & Alloy Steel
The most widely used structural metal in automotive manufacturing, offering an excellent combination of strength, formability, and cost-effectiveness.
Titanium
Titanium Alloy (Ti-6Al-4V)
Exotic high-strength metal prized for its strength-to-weight ratio
Properties
Category
Type
Platinum Group Metal (PGM)
Available Colors
Available Forms
Key Properties
- Exceptional NOx reduction catalyst
- Extreme corrosion resistance
- High melting point (1,964°C)
- Highly reflective surface
- Outstanding oxidation resistance
Technical Specifications
Density
12.41 g/cm³
Tensile Strength
951 MPa
Temperature Resistance
Up to ~1,964°C
Sustainability
Sustainability Rating
Rhodium is recoverable from end-of-life catalytic converters through autocatalyst recycling, which is increasingly critical given its scarcity. However, primary production is energy-intensive and concentrated in South Africa, raising supply security concerns. Secondary (recycled) rhodium now accounts for roughly 30% of supply.