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Naturally Occurring
Several sources of chromium in its trivalent state exist in nature and may be found in the air, water and surface soils, as well as in a wide variety of foodstuffs. Well-known sources of trivalent chromium include whole-grain products and cereals, legumes, processed meats, yeast, coffee and spices. Dairy products, on the other hand, contain relatively low concentrations of trivalent chromium.
Essential Nutrient
As a nutrient, trivalent chromium's most important role is the promotion of insulin action. Through this, it positively influences the metabolism of proteins, lipids, fats, sugars and carbohydrates. Experts consider a daily intake of 30 to 35 micrograms for adult males and 20 to 25 micrograms for adult females adequate, although excess amounts pose no significant risks, as trivalent chromium is neither toxic nor carcinogenic. A large portion of the average person's daily chromium intake comes from food processed or stored in stainless steel containers. Chromium deficiency problems, though rare, are recognized by symptoms such as weight loss, confusion and impaired glucose tolerance.
Corrosion Inhibitor
Chromium in both its trivalent and hexavalent forms serves as an excellent corrosion inhibitor, and is used widely as a coating for metals such as copper, aluminum, tin, silver and magnesium and their different alloys. Unlike hexavalent chromium, trivalent chromium coatings have limited coloring, poor electrical conductivity and sometimes require an additional sealant or topcoat; however, because of the former's toxicity, carcinogenicity and other health and environmental hazards, many industries now recognize trivalent chromium as the better alternative. The ammunition manufacturing, automotive, metal stamping and architectural industries also take advantage of trivalent chromium's corrosion-inhibiting properties.
Industrial Ingredient
Trivalent chromium's industrial applications are not limited to chrome plating. It also serves as an alloying element for steel, a fixative for textile dyes, a curing and tanning agent for leather, an inorganic paint pigment, a catalyst, a fungicide and a wood preservative. Trivalent chromium is also used in sensitizers for the photography industry, as well as in astringents and antiseptics. Because of its heavy industrial use, factory effluents and wastewater often contain trivalent chromium; however, it precipitates readily with lime or a diluted caustic solution and poses no grave threat to the environment.