Chromium is a naturally occurring, silver metal which exists in two different chemical forms in nature: trivalent chromium (otherwise known as chromium (III) or chromium 3) and hexavalent chromium (also called chromium (VI) or chromium 6). Trivalent chromium can be found in produce and grains and is an essential nutrient. Hexavalent chromium, by contrast, is a toxic substance whose industrial use gained a wide audience in the 2000 Hollywood movie "Erin Brokovich." According to the Toxics Use Reduction Institute (TURI), the adverse health effects of hexavalent chromium exposure includes skin rashes, ulcers, respiratory problems, liver damage, immune system disorders and cancer. Despite these hazards, hexavalent chromium is still used in a variety of industrial practices today.
Pigments and Mordants
The earliest applications of hexavalent chromium were as both pigments and mordants (substances that increase the absorption of pigments). Today it is still used for these purposes in the production of paints, inks, textile dyes and plastics. According to TURI, chromium (VI) is also used in leather tanning.
Chrome Plating
Chrome plating, often used for its decorative properties, uses chromium (VI) compounds. More than just decorative, TURI states that electroplated chromium can convey properties such as shininess and resistances to heat, corrosion and biological organisms. School furnishings, jet engines, gas turbines, wood preservatives and marine products including boats are some of the examples of products using hexavalent chromium for its durability properties.
Stainless Steel
The vast majority of hexavalent chromium used in industry today is in the production of alloys for products such as stainless steel. In addition to being used in the steel products themselves, chromium (VI) is also used in refractory bricks; also called firebricks, they are used in lining kilns, ovens and furnaces such as the those used to produce stainless steel. According to TUPI, hexavalent chromium was first used in these processes over 100 years ago for its heat resistant properties.
Hot Metal Work
Processes such as welding, and melting chromium metal are termed "hot work" because they are performed at high temperatures. According to the United States Department of Labor, these hot work processes are performed with nontoxic trivalent chromium. Unfortunately, when heated chromium (III) will undergo a chemical reaction known as oxidation, which will convert it to its hexavalent form, resulting in the production of chromium (VI). While hot works is not an example of the uses of hexavalent chromium, it does result in exposing the worker to the compound, and as such, alternatives to these processes should be sought.
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