Chromium trioxide

Chromium trioxide, CrO₃, is a dark red chromium(VI) oxide and strong oxidizing agent used in processes including chromium plating.

Chromium(VI): Chromium(VI) is the oxidation state in which chromium has a formal charge of +6 in compounds. Chromium trioxide’s oxidizing power comes from chromium in this high oxidation state.
Chromium plating: Chromium plating deposits a layer of chromium onto a surface by electrochemical or related processes. Chromium trioxide supplies chromium(VI) in traditional chromium-plating baths.
Chromium trioxide structure: Chromium trioxide forms extended chains of tetrahedrally coordinated chromium and oxygen atoms in its crystalline solid. Its polymeric solid structure contrasts with a simple isolated CrO₃ molecule.
Hexavalent chromium: Hexavalent chromium comprises chromium compounds in the +6 oxidation state, many of which are toxic and carcinogenic. Chromium trioxide is a particularly hazardous member of this chemical group.
Oxidation-reduction reaction: An oxidation-reduction reaction transfers electrons between chemical species, changing their oxidation states. Chromium trioxide accepts electrons as it oxidizes other substances.
Hard chrome plating: Hard chrome plating deposits a thick chromium layer to improve wear resistance and surface hardness. Chromium trioxide has been used in baths for this industrial coating.
Chromate: Chromate is the tetrahedral oxyanion CrO₄²⁻, containing chromium in the +6 oxidation state. Chromate chemistry is closely related to chromium trioxide in aqueous solutions.
Occupational cancer: Occupational cancer is cancer caused or increased by exposures encountered in the workplace. Workplace exposure to chromium trioxide can increase cancer risk.
Jones oxidation: Jones oxidation uses chromium trioxide in aqueous sulfuric acid and acetone to oxidize alcohols. This named reaction is a classic laboratory use of chromium trioxide.
Decorative chrome plating: Decorative chrome plating applies a thin chromium finish, usually over a layer of nickel. Chromium trioxide-based baths can produce the bright chromium surface.

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