
Photo: Wikimedia Commons, CC BY-SA 3.0
Rhodium is the rarest and most valuable of the platinum group metals. It is extraordinarily resistant to corrosion and has a very high melting point. Rhodium is used almost exclusively in three-way catalytic converters for automobiles.
Rhodium is irreplaceable in catalytic converters for meeting strict NOx emissions regulations, and over 80% of supply comes from South Africa.