DETERMINATION OF PARTIAL CURRENTS FOR CUNI AND CUCO ELECTRODEPOSITION USING ROTATING-RING-DISK ELECTRODES

An electrochemical stripping technique has been developed for the analysis of Cu alloys with iron-group metals (particularly Ni). The alloy is plated on the disk of a rotating ring-disk electrode. The electrode is transferred after plating to an HCl solution and stripped potentiodynamically. The Ni and Cu dissolve in the +2 and +1 oxidation states, respectively; the Cu(I) can be detected by oxidation to Cu(II) at the ring. From the ring and disk charges during stripping and the disk plating charge, the plating efficiency and the deposit composition can be calculated. The validity of the method was confirmed by inductively coupled plasma analysis. The technique has been used to examine the interrelationship of CuNi composition and plating conditions, varying the solution composition, rate of mass transfer, current density, and ambient atmosphere. A comparison of CuNi and CuCo alloys plated under the same conditions reveals that the Co alloys have a lower Cu content and are plated with higher current efficiency.