Experimental Research On Composite Electroplating Process Of Supercritical Double-pulse Reduction Graphene

Nickel coating has excellent lubricity,wear resistance,corrosion resistance,high hardness and thickness uniformity.It is one of the most widely used protective coatings in the automotive,petrochemical,marine,computer and other industries.However,with the continuous improvement of engineering design standards,the requirements for material corrosion and protection engineering are getting higher and higher,pure nickel plating can not meet the production needs,Nickel composite coating for the matrix metal,and reduced graphene oxide?RGO?were co-deposited and having excellent corrosion protection performance composite coating.Electrodeposition is divided into DC plating,single pulse plating and double pulse plating depending on the type of power supply.The double pulse current can dissolve the burrs and protrusions on the surface of the coating,improve the surface quality,reduce the concentration polarization and eliminate hydrogen embrittlement,and facilitate the manufacture of composite coatings with better quality.The solubility of the supercritical fluid has both gas diffusivity and liquid having fluidity,high permeability,high mass transfer rate characteristics.Applying a supercritical fluid to electrodeposition can improve the surface quality of the coating,improve the mechanical properties of the coating.The main research contents are as follows:?1?The order of influence of the double-pulse power parameters on the coating and the optimal electrical parameters were determined.The orthogonal test results of the double pulse power supply parameters show that the order of influence of the four double pulse power parameters on the microhardness of Ni-rGO composite coating is:Current density(J_a+)>forward pulse duty??_F?>reverse average current density(J_a-)>reverse pulse duty??_R?,followed by single factor experiments to determine the optimal Power parameters,ie J_a+=7A/dm²,?_F=0.35,J_a-=1.2 A/dm²,?_R=0.25.?2?The electrochemical behavior and microstructure of graphene in the coating were studied.The X-ray diffraction analysis,Raman spectroscopy,TEM electron microscopy observation of interface bonding and SEM and EDS analysis of graphene coating It is proved that the reduced graphene oxide nanoparticles are uniformly distributed in the coating layer,the structural integrity is maintained,and the interface between rGO and nickel crystal grains is tight,and no interfacial reaction occurs.Conditions such as supercritical fluid,double pulse power supply and reduction of graphene oxide change the preferred orientation of the coating to a certain extent,which is beneficial to the growth of nickel crystal along the?111?plane.?3?The effects of different process conditions on the properties of the coating were analyzed.By comparison of supercritical double-pulse Ni-rGO composite coating,supercritical DC electroplating Ni-rGO composite coating,supercritical double-pulse pure nickel coating,common Under the condition of double-pulse Ni-rGO coating,research shows that the supercritical double-pulse Ni-rGO composite coating has smooth surface and compact structure,and has reached the microhardness,wear resistance and corrosion resistance.At the same time,it was found that the addition of graphene to the coating can effectively increase the degree of disorder of the metal crystal plane,increase the growth point of nucleation,inhibit the continuous growth of crystals,refine the microstructure and improve the surface properties of the coating.The excellent mass transfer and miscibility of supercritical fluid CO2 can effectively improve the agglomeration of graphene in the coating and make the distribution of rGO more uniform in the coating.The double pulse current can reduce the concentration polarization and hydrogen evolution,promote grain refinement,and can dissolve the burrs and protrusions on the surface of the coating layer and improve the surface quality of the coating.