Rhodium

Rhodium is the most valuable of the platinum group metals.

Rhodium, abbreviated Rh, is a silver-white metallic element belonging to the platinum group metals. It is both highly resistant to corrosion and highly reflective. Being primarily found in ore bodies combined with platinum, palladium, gold and copper-nickel ores, rhodium is most often produced as a byproduct of nickel and platinum refining.

Since it is one of the rarest metals and has significant utility, the price of rhodium far exceeds that of other platinum group metals and any other precious metal, such as gold and silver. Because of this, Rhodium is considered the world's most expensive precious metal. It's efficiency as a catalyst for converting NO _x to N ₂ and O ₂ is the primary driver of rhodium demand, accounting for approximately 80% of demand. Aside from catalytic converters, some applications using rhodium are as a catalyst for nitric acid, in themocouples, and to coat optic fibers and optic mirrors. Rhodium is also less commonly used as electrical contacts, laboratory crucibles, and in the electrodes of aircraft spark plugs.

South Africa is the majority source of rhodium making up over 80% of total mined rhodium. Russia, Zimbabwe and Canada are the three other top producers, but in far lower quantities. Rhodium and other platinum group metals occur uncombined in nature, as well, in North and South America in river sands. Recycling of catalytic converters from scrapped vehicles is another important source of rhodium. Recycling supplies about 30% of annual rhodium production.

History

Rhodium was first discovered by William Hyde Wollaston, an English chemist and physicist. While developing a process to refine platinum, Wollaston came to incidentally discover both palladium and rhodium. Rhodium, from rodo (Greek word for rose), was named based on the color of some of its compounds. Throughout history there has been little need for rhodium as a commodity. This precious metal has historically been used as a finishing for jewelry, including in present times. In the 1970's rhodium began being used in the production of the three-way catalytic converter, increasing demand.

Jewelry

Throughout history precious metals such as gold and silver, and in modern times platinum and palladium, were used to create jewelry. Due to its scarcity, high melting point temperature and poor malleability compared to other precious metals, rhodium is used as plating in jewelry-making.

Rhodium plating gives jewelry a silvery-white, reflective appearance and will not irritate the skin, as other metals can. Its physical properties increase the shine, luster, and durability of the rhodium plated metal. Due to its silvery-white appearance, white metal (white gold or platinum jewelry) is primarily used for rhodium plating.

With its increased durability, rhodium plated jewelry is more resistant to scratching and in the case of silver it helps to prevent tarnishing as rhodium does not oxidize very easily. Even though rhodium plated jewelry is more scratch resistant, the rhodium plate can wear off and will require a re-application every couple of years. For jewelry that has a higher tendency for wear, such as necklaces and bracelets, plated rhodium will wear down much faster and require more frequent re-plating.

For people with nickel allergies, a benefit of rhodium plated jewelry is that it is hypoallergenic. White gold is a mixture of yellow gold with other metals, creating an alloy that is stronger than pure yellow gold, which gives white gold itself characteristic color. One of the metals in the alloy can be nickel. Because of this rhodium plated jewelry is seen as an option.

Demand for Rhodium Begins

It was only in 1970, when the United States Environmental Protection Agency (EPA) issued the Clean Air Act, that demand for platinum groups metals (platinum, rhodium, palladium) began to grow. The Clean Air Act necessitated the introduction of the catalytic converter to gasoline-powered automobiles, spurring demand for the metal catalysts they contained. Today rhodium's primary use is still as a catalyst in three-way catalytic converters, the primary emissions control mechanism in cars. This is because rhodium is a more effective catalyst than the other platinum group metals. According to S&P Global Platters, nearly 80% of all rhodium use is by the automotive industry.

Dieselgate

In 2015, it was discovered that Volkswagen violated the Clean Air Act (Dieselgate). The EPA found that laboratory emissions tests were altered to meet US standards. Emissions of nitrous oxides were up to 40 times higher in real-world driving. The trend following this scandal has shown a decrease in demand for diesel powered vehicles and an increase in the demand for gasoline powered vehicles in Europe. This change in demand for gasoline powered vehicles has increased the demand for rhodium.

Recent Increase in Demand

Prior to 2016, aside from the 2008 run-up to $10,000, the average rhodium price was $800 USD per Troy Ounce. Due to the low price, rhodium mining activity decreased in line with this lower demand. But starting in 2017, following the scandal, there has been a general increasing trend in daily rhodium prices. In early 2021, the spot price flirted with a high of $30,000 USD/oz, settling down towards $14,000 USD/oz into the last quarter of the year. Increasingly stringent limits on vehicle emissions in both China and India are spurring further demand for rhodium. In China, provincial governments have begun phasing in new vehicular emissions standards. In India, there is similar demand for platinum group metals, as officials there are also bringing the country's fleet of cars into line with European emission standards.

Rhodium Price over Time

Wild price swings affect many metals, but Rhodium prices have been among the more dramatic among the precious metals in recent years. A 20x increase in the rhodium price from January 2004 to more than $10,000 in June of 2008 was overshadowed more recently by the 37x rise from around $800 USD/Oz in January 2017 to around $30,000 USD/oz in March of 2021. The swings in rhodium pricing over time have mostly been related to vehicle emissions regulations and primary producer disruptions. In early 2024 the price of rhodium sat around $4500 USD/Troy Ounce, well off the 2021 peak.