CODEPOSITION OF SIC POWDERS WITH NICKEL IN A WATTS BATH

The effect of the silica layer of SiC powder on ionic adsorption was studied in a Watts nickel plating bath. PZC (point of zero charge) measurement suggested that SiC powder has a tendency to release H+ at pH > PZC (approximately 2.2), and the amount of Ni2+ adsorbed on the surface of the SiC increased with increased pH of the Watts bath. Experimental results showed that SiC powders not only catalyzed the adsorption of hydrogen atoms but also had a significant effect on hydrogen evolution during electrodeposition if the solution pH was less than or equal to 2.0 (approximately PZC). Furthermore, SiC powders have a shielding effect which prevents OH- from being released into the solution under an applied potential, which results in more Ni(OH)2 in the deposited layer. SiC powders also promote further adsorption of intermediates of nickel on the electrode surface, as shown by impedance studies.