NUCLEATION AND CRYSTAL-GROWTH IN GOLD ELECTRODEPOSITION FROM ACID-SOLUTION .2. HARD GOLD

The mechanism of nucleation and crystal growth of hard gold (Au-Ni) on a gold rotating disc electrode from a proprietary bath (Renovel N) wa s investigated using linear sweep voltammetry and chronoamperometry. I t was shown that two distinct mechanisms in two potential ranges are i nvolved in this process. Experimental current-time transients at more positive potentials were described in terms of three-dimensional progr essive nucleation and growth of right-circular cones. Time-independent inhibition of the vertical crystal growth was observed with an increa se in negative potential, similar to the soft gold deposition. A modif ied inhibition model, in which vertical growth rate was assumed to dec rease exponentially with time to a constant value, was derived to inte rpret experimental current-time transients recorded at more negative p otentials. The chronoamperometric transients were well described by th is model. Potential dependence of initial minima, maxima and final ste ady-state current was discussed.