Rarer than gold and essential for high-precision measurements, platinum is a strategic metal in modern industry. Present in thermocouples Used in furnaces, laboratories, and extreme processes, it ensures stability and reliability even at temperatures exceeding 1.600 °C. But what is this element and where else can it be used?
What is platinum?
Platinum has the chemical symbol Pt and atomic number 78. It is a silvery-white metal, extremely dense, malleable, and chemically inert, with low reactivity even in harsh environments.
It is one of the rarest elements in the Earth's crust, about 30 times rarer than gold. This scarcity helps explain its high commercial and industrial value. World production is largely concentrated in South Africa, followed by Russia and a few other countries.
The combination of rarity, chemical resistance, and thermal stability has made platinum an indispensable material in high-precision applications.
Platinum is approximately twice as dense as silver. A curious example of its historical value is the crown worn by Queen Elizabeth the Queen Mother, consort of King George VI, whose structure was entirely made of platinum. A solid cube of the metal, 15 centimeters on each side, weighs the equivalent of an adult man. Although the platinum wire used in thermocouples has a small diameter, its market value makes recycling economically viable.
The high price of platinum is linked to three main factors:
- Natural rarity
- Complex extraction process
- High industrial demand
Production concentrated in a few countries also directly influences global supply. History indicates that platinum began to be extracted in Ecuador about 2.500 years ago. Indigenous peoples used the metal in statuettes and ornaments. In the 18th century, the material arrived in Europe, where it underwent decades of scientific experimentation before gaining space in utensils and decorative objects.
At the end of the 19th century, platinum became popular in jewelry. It appeared in rings, necklaces, bracelets, and even diamond-studded crowns. During the First and Second World Wars, its use lost momentum, but it has grown again in recent decades. Today, platinum wedding rings symbolize durability and resistance, attributes associated with the metal.
Difference between platinum and gold
Platinum and gold are rare metals, but their scarcity manifests itself in distinct ways. The abundance of platinum in the Earth's crust is around 5 parts per billion (ppb), a number close to that of gold, which is about 4 ppb. The difference appears in global production: gold is extracted in a volume almost 17 times greater. While the world produces about 3.300 metric tons of gold per year, platinum does not reach 200 tons annually.
Most of the platinum mined comes from a few regions, with South Africa leading, followed by Russia and Canada. The total volume of platinum ever extracted from Earth is still significantly less than the total amount of gold mined throughout history, which reinforces its rarity in the market.
Physical properties
Gold is known for its warm yellow hue, associated with wealth for millennia. Platinum, on the other hand, has a white and silvery coloration, with a more sober appearance. Both are dense, but platinum weighs more. In jewelry of the same size, platinum pieces tend to be noticeably heavier.
The melting point also differentiates metals. Platinum melts at around 1.768 °C, which makes it more durable and resistant, but also more difficult and expensive to work with. Gold, with a melting point around 1.064 °C, is more malleable and easier to shape, a factor that explains its widespread presence in jewelry.
Chemical properties
Gold and platinum are noble metals. Resistant to corrosion and oxidation, they do not rust or lose their shine over time. This chemical stability makes them suitable for both long-term investments and industrial applications, as well as for parts that last for generations.
Source and availability
Gold is mined in several countries, including the United States, South Africa, Russia, Canada, Australia, and China. Platinum production is much more concentrated, with over two-thirds of the world's supply coming from South Africa, in addition to smaller volumes from Russia, Zimbabwe, and Canada.
Rarity and production
In 2024, global gold production was close to 3.300 metric tons. During the same period, platinum totaled approximately 186 tons. This difference helps explain why platinum usually fetches high prices, although fluctuations in industrial demand can alter this balance.
Why does a thermocouple contain platinum in its composition?
Platinum is widely used in thermocouples because it exhibits ideal properties for temperature measurement.
- Oxidation resistance
- Low chemical reactivity
- Electrical stability at high temperatures
- Low variation in performance over time.
In thermal sensors, the metal typically appears in alloys with rhodium, forming thermocouples capable of operating in harsh environments without loss of accuracy. These alloys allow for reliable measurements above 1.600 °C, something unfeasible for common metals.
Types of platinum thermocouples
Os S, R, and B thermocouple types These are the models with platinum platinum. See what each one looks like:
Type B thermocoupleIt uses platinum-rhodium alloys in both conductors. One contains approximately 70% platinum and 30% rhodium; the other, approximately 94% platinum and 6% rhodium. It operates between 800 °C and 1.800 °C, and is common in industrial furnaces and processes with high thermal demands.
Type R thermocouple: composed of a conductor with 87% platinum and 13% rhodium, and another of pure platinum. Measures temperatures up to 1.600 °C, frequently used in the metallurgical and steel industries.
Type S thermocoupleIt withstands temperatures up to 1.600 °C. One conductor is composed of 90% platinum and 10% rhodium; the other is pure platinum. It is adopted as a calibration standard, including for the melting point of gold, as well as for pharmaceutical and biotechnological applications.
These thermocouples offer high accuracy, thermal stability, a wide operating range, long service life, and reliability in oxidizing and inert atmospheres. In type B, the low thermoelectric potential eliminates the need for a compensating wire.
Advantages and disadvantages of platinum thermocouples
Among the advantages are high precision, stability over time, a wide temperature range, and resistance to harsh environments. They function well in oxidizing and inert atmospheres and, for short periods, in vacuum.
Limitations include low electrical sensitivity, reduced mechanical strength at very high temperatures, high susceptibility to contamination, and the high cost of precious metals, which increases the initial investment.
Platinum thermocouples are the preferred choice for high-temperature applications. They maintain accuracy over a range of 0°C to 1.800°C, with excellent stability in long-term measurements. Resistance to oxidation and corrosion extends service life and reduces the need for frequent replacements.
These sensors are compatible with a variety of measurement and control systems, which expands their versatility in industrial processes such as furnaces, reactors, and ovens.
Operating principles of platinum thermocouples
The operation is based on two conductors of different compositions connected in a circuit. When there is a temperature difference between the measuring junction and the reference junction, a thermoelectromotive force arises that is proportional to the temperature variation. The reading instrument converts this signal into the corresponding temperature value.
The signal strength depends only on the materials and temperatures at the ends, not on the length or diameter of the electrode. The structure of thermocouples varies according to the application, but usually includes electrodes, insulated protective tubes, and junction boxes.
What is platinum used for besides thermocouples?
Platinum is used in a variety of sectors beyond industrial instrumentation:
- Catalytic converters: used in vehicle emissions control
- Refining oil: acts as a catalyst in high-efficiency processes.
- Chemical industry: essential in the production of fertilizers, plastics and polymers
- Medical field: present in stents, pacemakers and catheters
- Electronics and jewelry: used in high-reliability sensors and luxury components.
Alutal helps you choose the correct platinum thermocouple.
The choice of thermocouple depends on the temperature range and environmental conditions. For applications between 1.000 °C and 1.300 °C, a single platinum-rhodium 10 thermocouple usually offers a good balance between stability and cost. In higher ranges, between 1.200 °C and 1.600 °C, the double platinum-rhodium 30/6 thermocouple offers greater durability.
The operating atmosphere also plays a role in the decision. Platinum thermocouples work best in oxidizing and inert environments, requiring extra care in reducing atmospheres or with metallic vapors. Proper insulation helps preserve the accuracy of measurements.
Alutal develops platinum thermocouples for industrial applications requiring precision, stability, and reliability.
- Types: -50 °C to 1.480 °C, suitable for laboratories, glass and ceramics.
- Type R: -50 °C to 1.760 °C, used in fusion and semiconductors.
- Type B: 0 °C to 1.820 °C, recommended for extreme processes.
Take the opportunity to explore our portfolio of solutions for temperature measurement.
