![]() At higher percentages, chromium makes steel highly resistant to many corrosive agents and environments. It was not until the early 1900s that the corrosion resistant-properties of steels containing percentages of chromium higher than 5 percent were noticed. Different amounts of carbon and the rate of cooling determine the final properties of steel.Īdding chromium to this mixture produces a harder steel by delaying the transformation that occurs as steel is cooled, and steels with 3 to 5 percent chromium were produced beginning in 1865. As steel cools it gains strength and rigidity, becoming stronger than iron. When this mixture is heated it reaches an extremely ductile stage and can be formed easily. But adding carbon to iron changes its microstructure and properties. Melting iron and pouring it into molds produces “cast iron” products that are brittle once they cool. ![]() Iron objects produced this way are only moderately hard, and they can bend in use. Iron, in its pure form, can be heated and then bent, hammered or “wrought” into many forms. Such mixtures of metals are called alloys. Steel is a mixture of iron with a small amount of carbon – around 1 percent. Beginning in the mid-1800s, iron manufacturers discovered that adding chromium to steel produced a harder, more useful metal. One of these areas was the metallurgical – metal manufacturing – industry. While chromium chemicals gained commercial importance rapidly in the pigment industries, chromium took longer to make an impression on other sectors. Kurtz left his mark on the world of color “Kurtz yellow” is still available in British color catalogues. This was perhaps the origin of the “yellow cab,” an idea exemplified today in New York City taxis. His chrome yellow achieved vogue status when the popular Princess Charlotte, daughter of British monarch George IV, had it used to paint her carriage. This did not give Kurtz a satisfactory profit, so he began producing other chrome compounds, specifically chrome pigments. Local manufacturers soon followed suit and competition drove the price down to 8 pence, about an eighth of the original price. In 1822 one of Vauquelin’s pupils, Andreas Kurtz, moved to England and began producing potassium bichromate and selling it to the English textile industry at 5 shillings a pound. Red and green pigments developed from chromium compounds were also used for printing wallpaper during this period. As early as 1820 the cotton and wool industries were using large amounts of chromium compounds such as potassium bichromate in the dyeing process. Chemically, the mordant binds with the dye and the fibers of the material, preventing bleeding and fading. To fix or stabilize the color, chemical agents called mordants were used. Often these dyes faded quickly if the dyed material was laundered. Before the advent of synthetic dyes, all dyes came from natural sources such as minerals and plants. The colorful chromium chemicals for which Vauquelin named chromium soon found practical application in the textile industry. This mineral was more plentiful than crocoite and the greater availability of chromium facilitated innovation and discovery in a wide range of industries. In 1799, a German chemist living in Paris found chromium in a dark, dull stone that would become to be called chromite. Others later discovered that the ruby also takes its red color from chromium. He found reds, bright yellows and deep greens and discovered that traces of chromium in a Peruvian emerald were responsible for its color. He named the element from the Greek word for color, “chroma,” because each chromium compound he produced was a brilliant color. The chromium element was isolated in 1797 by the French chemist Louis Nicholas Vauquelin. ![]() Chromite, the primary commercial ore, was not discovered until 1798. But the ore is too rare to be useful commercially. Artists also treasured fragments of crocoite for their beautiful, reddish orange color. A brilliant orange, the mineral was prized by early stone collectors for its four-sided crystals. Crocoite, also known as lead chromate, was discovered by a geologist in 1765 at the Beresof mine near Ekaterinburg, Siberia. The second, a mineral called crocoite, is unusual in appearance but extremely rare. The more common, called chromite, is a dark, dull stone that was easily overlooked. High amounts of chromium are found naturally in two minerals. Unlike other metals, chromium had no ancient or prehistoric uses. Hidden in Plain Sight Crocoite is unusual in appearance but rarely found.īeginning with the use of chrome plating in the art deco designs of the 1930s through its heyday in the cars, furniture and appliances of the 1950s and 1960s, chromium has been closely associated with the fast-paced modern world.
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