Precious metals are defined by their scarcity, high economic value, and exceptional resistance to corrosion or oxidation. The most well-known examples include gold, silver, and the platinum group metals (PGMs) like platinum and palladium. These materials are highly valued for their unique properties, extending their utility far beyond traditional financial or decorative purposes. Precious metals serve a wide array of high-performance functions in modern industry and technology.
Aesthetic and Investment Functions
The traditional use of precious metals centers on their inherent beauty, stability, and enduring value. Gold and silver are favored in jewelry manufacturing because of their excellent malleability and luster. Gold can be shaped into intricate designs and drawn into extremely fine wires, making it perfect for ornamental pieces.
These metals resist tarnishing and corrosion, ensuring objects maintain their shine over long periods. This chemical stability, combined with their rarity, has established them as a foundational global standard for investment. Physical forms, such as bullion bars and minted coins, are held by central banks and private investors as a store of wealth.
Their role as a hedge against inflation is dependent on their non-reactivity, allowing them to retain intrinsic value regardless of currency fluctuations. Their primary role in finance and art is driven by their physical beauty and inert nature, rather than their performance in chemical or electrical processes.
Essential Role in Electronics and Technology
Precious metals are integral to modern electronics due to their superior electrical properties, which prevent signal loss and component failure. Silver is the best electrical conductor of all metals, making it an ideal choice for specific contacts and wiring where maximum efficiency is required. However, silver can tarnish when exposed to sulfur, which limits its use in certain applications.
Gold’s unparalleled resistance to corrosion makes it the preferred material for plating connectors, switches, and wire bonds in computers and smartphones. A layer of gold maintains a reliable, low-resistance electrical pathway throughout the device’s lifetime. Palladium is also used in electronics, often found in multi-layer ceramic capacitors (MLCCs) and for plating electrical contacts.
Gold’s ductility allows it to be drawn into extremely fine wires, which connect the tiny contact pads on a microchip to the external leads of its package. The stability and high conductivity of these metals ensure that miniature components in circuit boards function reliably. This reliance on high-performance materials is crucial for the speed and longevity of electronic devices.
Catalytic Applications in Industry and Vehicles
The Platinum Group Metals (PGMs)—Platinum, Palladium, and Rhodium—are highly valued for their ability to function as catalysts, accelerating chemical reactions without being consumed themselves. The largest industrial application for PGMs is in automotive catalytic converters. These devices use a washcoat containing the PGMs to convert harmful engine exhaust pollutants into less toxic substances.
Platinum and palladium facilitate the oxidation of carbon monoxide and uncombusted hydrocarbons into carbon dioxide and water vapor. Rhodium is primarily responsible for reducing nitrogen oxides (NOx) into nitrogen and oxygen. The high surface area required is achieved by dispersing the metals as nanoparticles onto a substrate, making them highly efficient at high operating temperatures.
PGMs are also indispensable in chemical manufacturing. Platinum and rhodium are used in the production of nitric acid, a precursor for fertilizers, and in the petroleum industry to refine crude oil. Palladium is employed in hydrogenation reactions, a common process in the creation of various organic chemicals and pharmaceuticals.
Specialized High-Performance Uses
Several precious metals are utilized in highly specialized applications that demand extreme performance characteristics. Platinum is used extensively in medical devices due to its high density, biocompatibility, and resistance to corrosion within the human body. It is found in pacemakers, implantable defibrillators, and stents, where its inertness ensures it does not provoke a rejection response.
Specific platinum compounds are also incorporated into chemotherapy drugs, where they interfere with the DNA replication of cancer cells. Iridium, the most corrosion-resistant metal known, has a very high melting point and is used in components subjected to severe conditions. This includes high-temperature industrial equipment and specialized aerospace applications, such as spark plug contacts.
Rhodium is frequently alloyed with platinum to increase its hardness and is used to create laboratory crucibles that withstand extreme heat. Gold and palladium are also used in dental alloys due to their durability and non-reactivity in the mouth environment.