Effect of current density on the corrosion behavior of Ni-Co-P/SiC composite coatings prepared via ultrasonic pulse electrodeposition

To investigate the effect of current density on the corrosion resistance of ultrasonic pulse electrodeposited nanocomposite coatings, Ni-Co-P/SiC composite coatings were prepared on the surface of 45# steel at different current densities. The micromorphology, phase structure, water contact angle, corrosion behavior, and post-corrosion morphology of the coatings were characterized. The results showed that changes in current density led to changes in the surface morphology, SiC nanoparticle conent, and phase structure of the coatings. With the increase of current density, the SiC content, water contact angle, and corrosion resistance of the coatings all showed a trend of first increasing and then decreasing. At a current density of 4 A·dm⁻², the water contact angle reached its maximum value of 105.2°, the SiC content reached the highest value of 0.95at.%, and E_corr, I_corr, and R_ct reached their highest value of −0.446 V, the lowest value of 1.111 μA·cm⁻², and the maximum value of 6565.1 Ω·cm², respectively. The main forms of corrosion damage on the coating surface were pits, cracks, and spalling. Coatings that performed better in electrochemical tests exhibited a relatively flat surface morphology after corrosion. Coatings prepared at either too low or too high current densities had more significant defects on the surface after corrosion.