Synthesis and characterization of TiN nanoparticle reinforced binary Ni-Co alloy coatings

In the present work, TiN nanoparticle reinforced Ni-Co alloy coatings have been synthesized by pulse current electrodeposition under the assistance of magnetic and ultrasonic agitation. Various analytical techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) were used to explore the effects of current densities and agitation modes on the coating composition, morphology and structure of the electrodeposits. The corrosion resistance of the composite coating was examined by electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. The electrodeposits prepared under magnetic stirring exhibit nodular-protrusion morphology. The ultrasonic-assisted electrodeposited Ni-Co/TiN coatings are flatter, finer, and denser compared to that of magnetic stirring. The agitation mode affects the Co and TiN content in the composite coatings. The preferred orientation was (111) texture, which was gradually changed to (200) plane as the current density increased. The crystallite size was 14–17 nm, 11–14 nm for the magnetic and ultrasonic-assisted electrodeposited Ni-Co/TiN coatings, respectively. The roughness of the samples prepared under ultrasonic agitation was lower than that of magnetic stirring. EIS measurements show that the composite coating prepared at 6 A dm−2 under ultrasonic assistance exhibits the best corrosion resistance with maximum Rct during the whole immersion period. The ultrasonic-assisted electrodeposited Ni-Co/TiN coating has a denser structure and better corrosion resistance than that prepared under mechanical stirring.