Kinetics of the codischarge of nickel and chromium ions from oxalate-sulfate solutions into an alloy

The kinetics of individual and concurrent discharge of nickel and chromium ions from oxalate-sulfate solutions is studied. At a high cathodic potentia l (-1.2 V), the process of nickel deposition is sharply decelerated due to the surface passivation of the cathode with nickel oxides and the adsorptio n of organic products. During the coreduction of the ions with the formatio n of an alloy, the discharge rate of nickel ions is sharply decreased and t he deposition of chromium is accelerated, compared to the electrodeposition of individual metals. The phenomenon observed is accounted for by a sharp decrease in the rate constant of the electrochemical reaction of nickel dis charge on the surface of an alloy.