Utilization of Constant Current Chronopotentiometry to Synthesize a Co–Cr Alloy

Co–30 wt % Cr alloy was prepared by electro-deoxidation in molten calcium chloride at 1123 K. Constant current chronopotentiometry was used to prepare the alloy and investigate its mechanism of formation. The sintered starting material consisted of the solid solution Co x Cr y O 4 and some Co 3 O 4 ; the latter decomposes spontaneously to CoO in a low oxygen environment. Electro-deoxidation proceeds by the simultaneous rapid reduction of CoO to Co and the slower reduction of Co x Cr y O 4 to CaCr 2 O 4 and Co. The formation of CaCr 2 O 4 requires calcium ions from the melt, and it was reduced at a higher cathodic potential to Cr, releasing the calcium ions back into the salt. The overall process is under charge-transfer control in the range from 10 to 70 mA cm − 2 and mixed control from 70 to 140 mA cm − 2 enabling very fast reduction times to be achieved.