Electrochemical synthesis of a biomedically important Co–Cr alloy

Co–30 wt.% Cr alloy was prepared by electro-deoxidation in molten calcium chloride at 1123 K. A preliminary study was conducted into the preparation of the mixture of the Co3O4 and Cr2O3 and the formation of the non-stoichiometric, spinel structured, mixed oxide nominally labeled CoxCryO4. Constant voltage chronoamperometry was used both to prepare the alloy and to investigate its mechanism of formation. Electro-deoxidation proceeds by the simultaneous rapid reduction of CoO to Co and the slower reduction/substitution of CoxCryO4 to CaCr2O4 and Co metal. The final step of the electro-deoxidation is the reduction of CaCr2O4 to Cr metal, which alloys with the Co metal, and release of Ca2+ back into the electrolyte.