The Preparation And Study Of Electrodeposited Ni-SiC Nanocomposite Coatings

Ni-base coatings are not only used for decoration, but also used as functional coatings for resistance to corrosion, wear and heat (refractory coatings). In the past few years, Ni-base composite coatings have been applied more and more to electronic microelements, engine cylinder, etc. Owning to the rapid development of nanotechnology, scientists have paid more attention to Ni-base nanocomposite coatings applied by electrodeposition. In this paper, Ni-SiC nanocomposite coatings were prepared on brass substrate by electrodeposition, then the mechanism of plating process, coatings properties and SiC nano-particulates pretreatment methods were studied.With the method of the cathodic polarization curves,the deposition process of the nickel ion in the basis plating solution(without SiC particles) was analyzed, and the influence of processing parameters (current density, stirring intensity, solution PH, temperature, etc.) on the plating process and properties of basis plating solution was discussed, the processing conditions of nickel electroplating was determined primarily: current density can be chosed in the range of 10mA/cm~2 to 100mA/cm~2; stirring was helpful for the transportation of nickel ions during the electrodeposition process; the best choice of pH is 4.00 in the plating process; the ideal temperature of the plating bath is 50℃.The effects of different processing parameters and concentrations of SiC nanoparticles in the bath on hardness, corrosion resistance and organization structure of the Ni-SiC nanocomposite coatings were characterized by microhardness tests, electrochemical impedance spectroscopy test(EIS), X-ray diffraction(XRD)and scanning electron microscopy(SEM)methods, the following optimized preparation parameters for making Ni-SiC nanocomposite coatings with high hardness and excellent corrosion resistance were obtained: SiC particles concentration 6g/L, current density range 15~20 mA/cm~2, stirring rate 200rpm, plating solution temperatures is 50℃, pH value 4.00.Considering the problem of nanoparticles agglomeration, the effects of different SiC nanoparticulates pretreatment methods and surfactant content in the solution on the properties of the Ni-SiC nanocomposite coatings was studied and an effective SiC nanoparticulates pretreatment method was determined: SiC nanoparticulates were dispersed in Sodium Dodecyl Sulfate (SDS) aqueous solution for 30 min with magnetic stirring, then keep on magnetic dispersion for 10 min after adding plating bath. The Ni-SiC nanocomposite coatings exhibited an excellent corrosion resistance when the anionic-surfactant SDS concentration in the plating bath was 0.1g/L~0.2 g/L, and increasing the SDS concentration in the plating bath to 0.3g/L, the Ni-SiC nanocomposite coatings with high hardness could be made. But cationic-surfactant Cetyl Trimethyl Ammonium Bromide (CTAB) had negative effects and lowered the corrosion resistance and hardness of the Ni-SiC nanocomposite coatings.Finally, the effect of SiC nanoparticulates concentration and surfactants (SDS, CTAB) on the hydrogen evolution reaction process in blank solution (no metal ions) and electrodeposited nickel processes in plating bath was analyzed. The results show that SiC nanoparticulates with anionic-surfactant SDS pretreatment promoted the hydrogen evolution reaction process of blank solution, but cationic-surfactant CTAB had an opposite effect. Besides, SiC nanoparticulates with different surfactants pretreatment promoted the electrodeposited nickel processes in nickel plating bath.