A study on electrophoretic deposition of Ni nanoparticles on pitted Ni alloy 600 with surface fractality

In the present work, the electrophoretic deposition of Ni nanoparticles used for self-repairing of pits in organic suspension was investigated on pitted fractal Ni alloy 600 with respect to surface fractality of the pits. For this purpose, Ni nanoparticles prepared by levitation-gas condensation were dispersed into an ethanol solution with the addition of a dispersant. Four kinds of pitted fractal specimens with different surface fractal dimensions dF,surf were prepared by applying various anodic potentials above pitting potential to alloy 600 in aqueous 0.1 M NaCl solution. From the scanning electron microscopy (SEM) images, it was observed that the pits repaired under applied electric field E of 100 V cm-1 comprised more agglomerates of Ni nanoparticles than those repaired under E of 20 V cm-1. This suggests that the higher the value of E is, the more agglomerates of Ni nanoparticles are deposited on the specimen due to more depletion of OH- in suspension near the specimen surface. Moreover, the specimen with higher dF,surf gave a higher value of electrophoretic current Ip than one with lower dF,surf due to the increased electrochemical active area Aea of the specimen. From the above, it is concluded that the surface irregularities of the pit enhance the deposition of Ni nanoparticles on pitted fractal specimen during electrophoretic deposition.