Incorporation of the Zrc Nanoparticles into the Electroless Ni-P Coating and its Effect on the Corrosion Resistance and Micro-Hardness
The ZrC nanoparticles were synthesized by the sol-gel/carbothermal reduction method and then were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Afterward, the nanoparticles were loaded into the electroless Ni-P plating bath at concentration of 0.1 g. L-1. The SEM images showed that the nanoparticle incorporation causes to the decreasing of the coating nodule size. The cross-sectional SEM images showed the columnar structure of the coatings. Also, the nanocomposite coating showed higher thickness than the normal Ni-P coating. Energy Dispersive X-ray Spectroscopy (EDS) was used to confirm the incorporation of the nanoparticles into the coating. Also, the uniform distribution of the incorporated nanoparticles was confirmed by the EDS-mapping. The peaks corresponding to the ZrC nanoparticles were not seen in the XRD pattern of the nanocomposite due to high dispersion level of the nanoparticles in the coating. Electrochemical Impedance Spectroscopy (EIS) studies in 3.5 wt. % NaCl solution showed that the corrosion resistance of the electroless coating significantly improves by incorporating the ZrC nanoparticle so that the polarization resistance was increased from about 27.04 to 43.08 kΩ. cm2. The results of the potentiodynamic polarization tests at the same corrosive media showed that the corrosion current density value was decreased from about 1.70 to 0.87 μA. cm-2 after incorporation of the nanoparticles. Also, the Vickers micro-hardness of the nanocomposite coating was measured to be around 720 which was much higher than that of the normal electroless coating (468). Finally, the role of the electrostatic attraction in trapping of the ZrC nanoparticles into the matrix of the electroless coating was revealed by determination of charge type of the nanoparticles and alloy surface.
Iranian Journal of Surface Science and Engineering, No. 39, 2019
31 - 46
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