A comparison of the surface chemistries of chromium electroplated finishes

SUMMARYThe surfaces of chromium electroplated from trivalent and hexavalent electrolyte, both aged and fresh, from industrial and laboratory cells have been examined by scanning electron and atomic force microscopy; as well as Auger and X-ray photoelectron spectroscopy. The surfaces are oxidised: the oxide on “trivalent” chromium is typically 1.5 nm thick; that on conventional “hexavalent” chromium is 1.1 nm thick. The oxide on hexavalent chromium is less contaminated than that on trivalent chromium. Similarly the deposits from the Cr(VI) electrolyte are purer than those from Cr(III) solutions. The rate of deposition of chromium from Cr(III) electrolytes depends critically on the bath management.