influence of b4c nanoparticles on corrosion characteristics of ni matrix nanocomposite coatings fabricated via pulse electroplating technique

The ni-b4c 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 = 1 a/dm², γ = 50%, and f = 10 hz. embedding b4c nanoparticles (nps) into the nickel matrix significantly reduced the nickel crystallite size for the primary (111) and (200) crystal planes. increasing the pulse current density from 1 to 4 a/dm² caused a substantial decrease in the incorporation rate of b4c nps, from 5.5 to 2.9 vol.%. however, an increase in the duty cycle from 25 to 50% and the pulse frequency from 1 to 10 hz raised the incorporation rate to 5.5 vol.% and 4.6 to 3.9 vol.%, respectively. surprisingly, the incorporation of b4c led to an increase in the corrosion current density from 2.301 to 4.541 µa/cm². increasing the pulse current density from 1 to 4 a/dm² and the duty cycle from 25 to 50% notably decreased the corrosion current density from 4.541 to 1.375 µa/cm² and from 7.243 to 4.541 µa/cm², respectively. conversely, the minimum corrosion current density of 0.599 µa/cm², deposited at 1 hz, increased significantly to 4.541 µa/cm² at 10 hz, while the b4c nps content increased from 3.9 to 5.5 vol.%, possibly due to a more uniform distribution of b4c nps at 1 hz. the ni-b4c specimen deposited at 1 hz exhibited a higher rct compared to the pure nickel sample under baseline conditions, indicating strong consistency between the eis and potentiodynamic results.