Electrochemical Deposition and Nucleation/Growth Mechanism of Ni–Co–Y(2)O(3) Multiple Coatings

Ni–Co alloy and Ni–Co–Y(2)O(3) multiple coatings refined with nano-Y(2)O(3) particles were fabricated by ultrasonic-assisted electrochemical deposition in an acid sulfamate bath. Linear sweep voltammetry (LSV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) techniques were applied to investigate the nucleation/growth process of composite coatings in co-deposition. The LSV results indicated that the incorporation of nano-Y(2)O(3) particles with the Ni–Co matrix shifted the initial deposition potential to a more positive potential and decreased cathodic polarization. For both coatings, the nucleation/growth process approximately agreed with the Scharifker–Hill instantaneous nucleation model. Nucleation parameters, including active nucleation sites (N(0)) and nucleation rate (A) of the composite, were higher when the measured potential range was between −1.05 V (vs. SCE) and −1.20 V vs. SCE, when compared with the Ni–Co alloy, and the observed AFM images of the coatings were in good agreement with the calculated nucleation parameters (using the Marquardt–Levenberg algorithm) of experimental curves. EIS testing indicated that the charge transfer resistance of the composite was lower in electrodeposition. The incorporation of nano-Y(2)O(3) particles in the matrix changed the preferred orientation of coatings and produced a more uniform and compact deposit layer with finer grains.