SINUSOIDAL POTENTIAL SCAN-BASED NICKEL EL ECTRODEPOSITION ON ANODIZEDALUMINUM .2. INFLUENCES OF SCAN POTENTIAL AND ANODIZED FILM THICKNESS

Influences of the cathodic potential and the anodized film thickness o n the electrodeposition of nickel on anodized aluminum were investigat ed in an NiSO4(5wt%)-H3BO3(4wt%)bath under a sinusoidal potential scan . When the amplitude of the potential scan (Eo) was varied in the rang e 1 similar to 38V while the anodized film thickness was fixed at 15 m u m, three current peaks (I-s, I-1 and I-2)appeared at -3.43V, -10.82, and -12.40V, vs. SCE, respectively. The amounts of Ni deposited at I- 1 were found to coincide with those of Ni2+ estimated film thickness w as varied in the range 0.2 similar to 15 mu m with Eo fixed at 15V, th e electrolytic behavior changed critically at the thickness of about 2 mu m. Hydrogen evolution took place almost exclusively on the films t hinner than 2 mu m, while nickel deposition occurred on the thicker fi lms leading to a steep decrease in the brightness index of the films. Based on these results, mechanisms of nickel electrodeposition and hyd rogen evolution were discussed.