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

Abstract

Abstract 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/dm 2 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.