Hexavalent chromium is a collective term for chromium compounds that contain Cr(VI), where chromium has an oxidation state of +6. The most extensive use of metal is in "chrome plating," where it is used to enhance luster, hardness, and corrosion resistance.
However, hexavalent chromium compounds are highly toxic. Although they were widely used in plating applications, their use has become problematic due to soil contamination.
Consequently, hexavalent chromium is being phased out, particularly in chromate conversion coatings used in zinc plating.