Corrosion resistance of Ni-Co alloy and Ni-Co/SiC nanocomposite coatings electrodeposited by sediment codeposition technique

Corrosion resistance of Ni-Co alloy and Ni-Co/SiC nanocomposite coatings electrodeposited in a modified Watts bath using sediment codeposition (SCD) technique was evaluated by potentiodynamic polarization measurements in the 3.5% NaCl solution and studied as a function of deposition conditions In order to characterize the morphology, chemical and phase compositions of the coatings, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD) were utilized, respectively. It was observed that the cobalt content in the Ni-Co alloy coatings was increased through an anomalous behavior by increasing the cobalt concentration in the electrolyte. The highest percentage of SiC nano-particles (8.1 vol.%) in the Ni-Co/SiC nanocomposite coatings was achieved at 3 A/dm2 deposition current density and 5 g/l particle concentration. SEM and EDS analysis illustrated that SiC nano-particles were distributed uniformly throughout the nanocomposite coatings. The potentiodynamic polarization tests indicated that the corrosion resistance of the Ni-Co alloy coatings was varied as a function of the cobalt content, and the corrosion resistance of the Ni-Co/SiC nanocomposite coatings was markedly higher than the corrosion resistance of the Ni-Co alloy coatings. Among the studied coatings, Ni-Co/SiC nanocomposite coatings containing 8.1 vol.% SiC nano-particles exhibited the best corrosion resistance.