Cadmium

Cadmium was discovered around the year 1820. The chemists Carl Wilhelm Gottlob Kastner, Friedrich Strohmeyer, and the physician Johann Roloff independently came across the element at roughly the same time.

For a long time, cadmium sulfides and selenides were used as pigments, ranging in color from yellow to reddish-brown. Cadmium yellow, for instance, was detected in Claude Monet’s painting "Bordighera."

Starting in 1925, Bayer AG began industrial production of cadmium yellow. Until 1980, cadmium yellow was the official color of the German Federal Post Office. Even today, the yellow mailboxes in Germany still bear this color.

Early reports from the 19th century already pointed to the harmful health effects of the metal. Nevertheless, cadmium iodide was used at the time to treat swollen joints and frostbite.

The majority of cadmium produced is used in rechargeable nickel-cadmium batteries (NiCd batteries). These batteries provide essential emergency power functions to ensure the safety of passengers in the event of a power outage in subways, high-speed trains, and aircraft.

In consumer products, the use of NiCd batteries has been banned in the EU since 2017.

Larger quantities of cadmium are also used for corrosion-resistant coatings (cadmium plating) on steel, aerospace components, and fasteners. However, their use is restricted in the EU due to associated health risks.

Another economically valuable compound is cadmium sulfide (CdS), a bright yellow pigment known as cadmium yellow. It is used in high-quality paints and artist pigments due to its color stability.

Cadmium telluride (CdTe) is used in thin-film photovoltaic cells, the second most common solar technology after silicon. The market leader in this field is the U.S. company First Solar.

Approximately 24,000 tonnes of refined cadmium are produced globally each year.

Sphalerite is the most economically important zinc ore mineral and also contains small amounts of cadmium. Cadmium is primarily obtained from zinc ores and concentrates.

The leading production countries are China, South Korea, Canada, and Japan.

Korea Zinc is considered the most important cadmium producer. Other major players include Nyrstar (Trafigura), Teck Resources (Canada), Hindustan Zinc (India), Glencore (Switzerland), and Boliden (Sweden). In China, the Zhuzhou Smelter Group is regarded as the leading cadmium producer.

In the EU, the recycling rate for cadmium is estimated at around 30 percent.

Batteries with other chemical compositions, particularly lithium-ion batteries, can replace NiCd batteries in many applications.

Where the surface properties of a coating are not critical (e.g. for fasteners in aircraft), coatings such as zinc-nickelcan replace cadmium in many coating applications.

Cerium sulfide is used as a substitute for cadmium pigments, primarily in plastics. Barium stabilizers can replace barium-cadmium stabilizers in flexible polyvinyl chloride (PVC) applications.

Thin-film technologies based on copper indium gallium diselenide and perovskite materials continue to be researched, but are not yet commercially viable.