Hexavalent Chromium Terminology and Uses

Question: What other terms also refer to hexavalent chromium, and what are its common uses?

Answer: Hexavalent chromium is used in paints and dyes, anti-corrosive products, conversion coatings (such as passivation), and many other applications. Because hexavalent chromium is also toxic and carcinogenic, its use is widely regulated, including under the EU Restriction of Hazardous Substances (RoHS) Directive; the Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) Regulation; and California Proposition 65.

Compliance efforts may be complicated by the fact that hexavalent chromium is referred to in many different ways, ranging from simplified terms to complex chemical names. All of the following terms refer to hexavalent chromium:

  • Chromium VI, CR-VI (CAS 18540-29-9)
  • Chromium (VI) oxide
  • Chromium 6, CR-6
  • Hex chrome
  • Chromium trioxide, CrO3 (CAS 1333-82-0)
  • Chromic anhydride

Other forms of chromium exist and may sometimes be confused with hexavalent chromium, since the names and terms are similar. The following substances are not hexavalent chromium, and in some cases, they may be used as safer alternatives:

  • Trivalent chromium (Cr-3, "Tri chrome") is safe to handle and is sometimes sold as a dietary supplement.
    • Trivalent chromium is also used in conversion coatings, but these may be more expensive and may not prevent rust as well as hexavalent chromium.
    • Trivalent chromium is not restricted/regulated, and is generally not associated with the same risks as hexavalent chromium.
    • Trivalent chromium should not be confused with chromium trioxide (another name for hexavalent chromium).
  • Hard chrome plating (Cr-0) is inert and safe; it is not restricted/regulated.

This article is current as of 2021-08-03.

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