Study On Electroless Plating Ni-P Alloy On Copper And Its Corrosion Resistance

Copper has many good points of very good ductility,cold resistance,electrical conductivity and thermal conductivity.It is urgent to improve the corrosion resistance of copper and copper alloys to overcome the shortcomings of poor corrosion resistance of copper in practical applications.In this paper,electroless plating method was used to prepare Ni-P coating on the surface of copper.The structure of the coating surface is improved to raise the corrosion resistance of copper by changing the preparation parameters.The research results of the Ni-P binary alloy coating show that with the extension of the deposition time,the small Ni-P particles formed on the active site grew into cells,and then gradually fused to cover the entire surface of the substrate.At the same time,the thickness of the coating increases with the extension of the deposition time,the density increases,and the P content gradually increases from the inside to the outside.The study found that the p H value,sodium citrate and temperature of the Ni-P binary alloy plating solution will affect the deposition rate and the stability of the plating solution.The coatings prepared under different process parameters have a typical cell structure,and the coatings are all amorphous.Changes in the preparation process parameters will affect the degree of agglomeration of cells on the surface of the coating.Orthogonal test to determine the optimal combination of basic plating solution.The corrosion performance test results show that under different process parameters,the anode polarization curves of the coatings all show passivation and the corrosion current density has a certain decrease.During the immersion process,a passivation film is first formed.With the extension of the immersion time,the corrosive medium penetrates and then local corrosion and pitting occur.However,after a long period of immersion,the coating still has a high impedance modulus,indicating that the coating has excellent corrosion resistance.In order to reduce the micropores of the Ni-P binary alloy coating,Cu SO4 and nano-Ce O2 are added to the preferred basic plating solution to achieve the preparation of Ni-P multi-element alloy and composite coating,and then the coatings are silanesealed.The research results of Ni-P multicomponent alloy and composite coating indicate that the typical cell structure of the coating does not change under different process conditions,and they are all amorphous structures.The addition Cu SO4 makes the coating more smooth and dense.The addition of nano-Ce O2 can improve the density of the coating,but too much Ce O2 will make the surface agglomeration phenomenon more obvious.When Cu SO4 and Ce O2 are added together,the surface morphology of the coating is related to their mass fraction ratio.When the mass ratio of Ce O2 to Cu SO4 is 1:2,the surface of the coating is dense and there are few agglomerates,the morphology is the best.The corrosion performance test results show that under different additives,the anode polarization curves of the coatings have obvious passivation intervals and the corrosion current density of the coating after the silane sealing treatment is reduced by 3 orders of magnitude.During the immersion process,the impedance spectrum of the plating layer showed a similar trend,that is,a passivation film was formed first,and then the corrosive medium will destroy the passivation layer and penetrate into the plating layer so pitting corrosion occured.After the silane sealing treatment,the capacitance arc diameter of the coating increased significantly,and the low-frequency impedance value was even 3 times of that untreated coating,it can be seen that the silane sealing treatment can obviously optimize the corrosion resistance of the coating.