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Chromium Corrosion

Chromium was discovered in 1797 by Vauquelin, who prepared the metal the next year. Chromium is a steel-gray, lustrous, hard metal that takes a high polish. The principal ore is chromate, which is found in Zimbabwe, Russia, Transvaal, Turkey, Iran, Albania, Finland, Democratic Republic of Madagascar, and the Philippines. The metal is usually produced by reducing the oxide with aluminum. A modern and comprehensive document on the subject is the second edition of the classic CORROSION BASICS textbook. Some excerpts of that document are used here.

Chromium is used to harden steel, to manufacture stainless steel, and to form many useful alloys. Much is used in plating to produce a hard, beautiful surface and to prevent corrosion. Chromium is used to give glass an emerald green color. It finds wide use as a catalyst. All compounds of chromium are colored; the most important are the chromates of sodium and potassium and the dichromates and the potassium and ammonium chrome alums. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather.

Other compounds are of industrial value. Lead chromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industries for anodizing aluminum. The refractory industry has found chromite useful for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure. Many chromium compounds are toxic and should be handled with proper safeguards. Natural chromium contains four isotopes. Sixteen other isotopes are known.

Chromium and its compounds are used in metal alloys such as stainless steel, protective coatings on metal, magnetic tapes, and pigments for paints, cement, paper, rubber, composition floor covering and other materials. Other uses include organic chemical synthesis, photochemical processing and industrial water treatment. In medicine, chromium compounds are used in astringents and antiseptics. Chromium encounters many industrial applications, including its uses in steel and nonferrous alloys, metal-plating, refractory materials, chromate pigments and chromate preservatives.