Rhodium is a member of the platinum group metals and has been found as a minor mineral in places like South Africa, Finland and Ontario, Canada. It is also an alloying agent in some metals, such as steel, nickel and cobalt.
It is rare in the earth's crust, with an average crustal abundance of only 0.0002 parts per million. It can be found in trace amounts as an impurity in platinum, palladium and other minerals, and as a minor component in base metal sulfide deposits.
Most of the world's rhodium is used in catalytic converters for vehicles that produce gasoline or diesel. These devices are designed to clean emissions by converting harmful pollutants into less harmful substances, such as nitrogen oxide and hydrocarbons.
As a result, the demand for rhodium has grown and remains strong. This is due to the increasing restrictions on car emission levels, as well as a growing global awareness of the issue of pollution.
Some of the most common rhodium-containing items that you can find in scrap include wire, sheet, rods and foil that come from aerospace manufacturing, rotors that are used in jet engines and thermocouple wire that is used in advanced medical and research facilities.
There are also some rhodium-plated objects that you can find in scrap, such as utensils and tools. These objects can turn tarnished and discolored over time, depending on the quality of the item and how much rhodium plating has worn off.