Preparation And Properties Of Ni-P-CS Composite Coatings

Carbon nanomaterials exhibit superior properties inertia and lubricity as well as preferable hydrophobicity available to prepare compound material for enhanced phase,but less commonly applied in the metal corrosion and protection area.Carbon nanomaterials from soot,formed by candle incomplete combustion,were adopted in this study as second phase material,to prepare Ni-P-CS composite electroless solution with uniform suspension and dispersion of carbon nanoparticles,and realize Ni-P-CS composite coating preparation on Q235 low carbon steel.Scanning electron microscopy（SEM）and X-Ray diffractometer（XRD）were conducted to characterize the structure and appearance of compound coating,and to investigate the relationship between the addition of carbon nanoparticles to the electroless solution and the carbon content of the composite coating.Besides,electrochemical impedance spectroscopy and dynamic potential polarization as well as immersion corrosion tests were implemented to explore the effect of carbon nanoparticles addition exerted on the corrosion resistance of compound coating,and heat treatment process in various temperatures were applied in the stiffness and friction and wear properties.The results indicate that:（1）the incorporation of candle soot decreases the chemical deposition reaction rate of the nickel-phosphorus coating and thus the chemical deposition rate.（2）The incorporation of second phase particles inhibits the phosphorus elements deposition in the electroless solution,and the incorporation of 1.0 g L^-1 and 1.5 g L^-1 enables the crystalline state exhibition of nickel elements.Besides,the incorporation of second phase particles（CS）leads to the reduction in the coating particles filling and pores.On the composite coating surface,nodular protrusions can be found,with the candle soot agglomerates at the tips of nodular protrusions.（3）Under the condition of controlling chemical deposition time,temperature and p H value during the composite coating preparation,the thickness of the Ni-P-CS composite coating shows no significant change.（4）The corrosion resistance of Ni-P-CS composite coating in 3.5%Na Cl aqueous solution exhibits significant improvement,with the protection efficiency peaking at 81.53%,increasing 34.45%based on the Ni-P coating with a protection efficiency of 47.08%.the composite coating shows a higher corrosion potential and lower corrosion current,indicating the lowest corrosion tendency of Ni-P-CS coating,and the optimal incorporation content is1.0 g L^-1 in nanoparticles for the second phase.（5）The corrosion resistance of the Ni-P-CS composite coating in various media is ranked as:10wt.%Na OH>10wt.%HCl.（6）Benefiting from the self-lubricity of carbon nanoparticles,significant enhancement can be found in the wear resistance of Ni-P-CS composite coatings.Smaller friction coefficient and enhanced wear resistance can be seen compared with single Ni-P coating.（7）The heat treatment process cannot achieve better performance in the wear resistance of the composite coating.The reason is that due to the existence of the candle soot without resistance to high temperature,the thermal fatigue of the composite coating aggravates during the heating process of heat treatment,and the appearance of chaps and cracks in the coating surface reduces the wear resistance of the composite coating during the friction and wear process.