Influence of B۴C Nanoparticles on Corrosion Characteristics of Ni Matrix Nanocomposite Coatings Fabricated via Pulse Electroplating Technique

The Ni-B۴C nanocomposite coatings were fabricated via pulse electrodeposition on a copper substrate, and the effects of pulse current density, duty cycle, and pulse frequency on the microstructure, morphology, and corrosion characteristics were assessed. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) tests were employed. The baseline electrodeposition conditions were set at i = ۱ A/dm², γ = ۵۰%, and f = ۱۰ Hz. Embedding B۴C nanoparticles (NPs) into the nickel matrix significantly reduced the nickel crystallite size for the primary (۱۱۱) and (۲۰۰) crystal planes. Increasing the pulse current density from ۱ to ۴ A/dm² caused a substantial decrease in the incorporation rate of B۴C NPs, from ۵.۵ to ۲.۹ vol.%. However, an increase in the duty cycle from ۲۵ to ۵۰% and the pulse frequency from ۱ to ۱۰ Hz raised the incorporation rate to ۵.۵ vol.% and ۴.۶ to ۳.۹ vol.%, respectively. Surprisingly, the incorporation of B۴C led to an increase in the corrosion current density from ۲.۳۰۱ to ۴.۵۴۱ µA/cm². Increasing the pulse current density from ۱ to ۴ A/dm² and the duty cycle from ۲۵ to ۵۰% notably decreased the corrosion current density from ۴.۵۴۱ to ۱.۳۷۵ µA/cm² and from ۷.۲۴۳ to ۴.۵۴۱ µA/cm², respectively. Conversely, the minimum corrosion current density of ۰.۵۹۹ µA/cm², deposited at ۱ Hz, increased significantly to ۴.۵۴۱ µA/cm² at ۱۰ Hz, while the B۴C NPs content increased from ۳.۹ to ۵.۵ vol.%, possibly due to a more uniform distribution of B۴C NPs at ۱ Hz. The Ni-B۴C specimen deposited at ۱ Hz exhibited a higher Rct compared to the pure nickel sample under baseline conditions, indicating strong consistency between the EIS and potentiodynamic results.

کلیدواژه ها:

Ni-B۴C nanocomposite ، Pulse electrodeposition ، Microstructure ، corrosion ، potentiodynamic polarization