Abstract:
The interest of this research was to investigate the effect of cow horn particle (CHp) incorporation on the surface morphology, mechanical, tribological and corrosion properties of electroless Nickel Phosphorous (Ni-P) and Nickel Zinc Phosphorous (Ni-Zn-P) coatings on mild steel. The effect of post plating heat treatment on the properties of the Ni-P and Ni-Zn-P composite coatings were equally studied. Various quantitative and qualitative methods were used to analyze the coatings. The surface properties of the coatings were studied by scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Hardness tests were done to determine the mechanical property of the coating, wear, coefficient of friction and atomic force microscopy (AFM) tests were used to reveal the tribological properties of the coating and the corrosion properties were studied by open circuit potential (OCP) and Tafel polarization tests. The SEM results indicates grain filling as a result of CHp incorporation, the XRD results shows grain refinement and grain growth resulting from the CHp incorporation and heat treatment. Hardness test results indicate an increase and a decrease in hardness values with CHp incorporation for Ni-Zn-P and Ni-P composite coatings respectively with optimum hardness values of 177.73HV and 246.65HV got for as plated Ni-Zn-P/8gCHp and Ni-P/6g CHp, heat treated at 8000C respectively. Wear results indicates a 30% increase in the wear resistance of the Ni-P and Ni-Zn-P composite coatings with CHp incorporation. Heat treatment had a detrimental effect on the wear resistance of the coating as it reduced its self-lubricity. AFM results indicates that the coating followed the surface profile of the substrate. Corrosion results indicate that the corrosion resistance of the Ni-Zn-P was improved by up to 50% while that of Ni-P slightly decreased with CHp incorporation into the coating. Heat treatment of the composite coatings reduced its corrosion resistance and the corrosion trends show passivation tendency of most of the coatings. Finally, the improvement in the deposition rate and surface morphology change as a result of CHp incorporation showed that CHp can function as a good surfactant for electroless Ni-P and Ni-Zn-P coatings and the corrosion and wear results of the Ni-P and Ni-Zn-P composite coatings showed that they are good candidates for materials subjected to excessive corrosion and wear in sea water environment.
