by U.S. Geological Survey Wednesday, June 13, 2018
Amy C. Tolcin, a mineral commodity specialist for the U.S. Geological Survey, compiled the following information on cadmium, a minor metal that is important for its use in rechargeable batteries.
The element cadmium was discovered in 1817 by Friedrich Stromeyer, a professor of chemistry at the University of Göttingen in Germany. Stromeyer noticed that a yellowish glow would occur when heat was applied to certain samples of calamine, a zinc-carbonate. This was unusual as the reaction was expected to be colorless. After further testing, Stromeyer deduced that an unknown metallic impurity in the carbonate caused the color change. He called the new metal “cadmium” after “kadmeia,” the Greek word for calamine.
Cadmium is a transitional metal with a crustal abundance of about 0.15 parts per million, which is close to that of antimony and indium. The occurrence of cadmium minerals is rare; the element most often substitutes for zinc or occurs as a sulfide inclusion in zinc minerals.
Commercial production began in Germany in the 1880s as a byproduct of the smelting of zinc ores from Silesia (now part of Poland). Cadmium production expanded to the United States in 1907 and increased substantially with the introduction of the cadmium electroplating process in 1919 and the use of cadmium alloys in automobile engines in the 1930s.
Production of cadmium in the United States peaked in the late 1960s and then declined, as production moved to other global regions because of environmental concerns about cadmium’s toxicity. The U.S. Occupational Safety and Health Administration calls cadmium an extremely toxic metal and limits worker exposure.
Cadmium is primarily consumed for the production of rechargeable nickel-cadmium batteries (80 percent), followed by pigments, coatings and stabilizers. Nickel-cadmium batteries are used to power consumer products (commonly power tools) and to provide emergency backup power in industrial applications and aircraft electrical systems.
Cadmium pigments can range in color from golden yellow to maroon, depending on other minerals in the pigment. The pigments are predominantly used to color plastics that are processed at higher temperatures, because the pigments can withstand the elevated temperatures without degrading.
Cadmium coatings are applied to steel and other nonferrous moving parts in certain applications because of cadmium’s superior corrosion resistance under alkali conditions and its low coefficient of friction. Cadmium stabilizers are used in polyvinylchloride (PVC) to slow the degradation process that takes place when PVC is exposed to heat and ultraviolet radiation.
For more information on cadmium and other mineral resources, visit http://minerals.usgs.gov/minerals.
Cadmium production and consumption:
Cadmium is primarily extracted from lead and zinc ores and concentrates.
About 75 percent of the world’s supply of cadmium is produced as a byproduct at zinc refineries, and the remainder is recovered from nickel-cadmium battery recycling facilities.
Most of the world’s cadmium supply originates from China, Japan and the Republic of Korea, with China leading the world in production.
Currently, the United States is a net exporter of cadmium and accounts for 6 percent of the world’s reserves.
Leading consumers of refined cadmium are China, Belgium and Japan.
Cadmium telluride thin-film solar cells are flexible and thinner than traditional silicon wafer cells.
Cadmium is efficient at absorbing neutrons, and cadmium alloys are often used in nuclear reactors to control the rate of fission.
The U.S. government once stockpiled cadmium for use in critical military applications.
Cadmium metal can be cut with a knife.
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