Research On Preparation Of Electrolytic Thick Nickel And The Effect Of Hot Rolling Process On Its Performance

At present,compared with foreign countries,the preparation of domestic electrolytic thick nickel,when it is applied to electroplating anode,it has the problems of loose,uneven, and large amount of anode residue.In view of this, this article uses the electric deposition method to domestic electrolytic thick nickel two times electro deposition and using Gleeble3500 thermal simulation test machine to carry out hot rolling process of electrolytic thick nickel.The pretreatment process,electroplating process and the influence of hot rolling process on the properties of electrolytic thick nickel were studied systematically.The Morphology and microstructure of the coatings were observed by field emission scanning electron microscope and optical microscope,crystal orientation, internal stress and grain size of the coating were tested by X ray diffraction,electrochemical properties of the coating were analyzed by electrochemical workstation.The main work and experimental results are as follows.(1) In pretreatment process,When using the activation process with etching,there are nickel-starting sheet of the fine crystal, uniform compact nickel in titanium- mother board.The pretreatment process can reduce internal stress and improve the adhesion of the nickel coating with the substrate.It has a certain combination of strength with titanium- mother board, easy to peel off but not burst. The etching system is hydrofluoric acid,nitric acid and hydrogen peroxide solution, The activation system is sodium fluoroborate and nitrite solution.(2) Sodium dodecyl sulfate as a kind of anionic surfactant, has good wetting effect,When the addition amount of 0.075g/L can effectively prevent pinholes, and the nickel coating surface is intact, but not obvious defects. Cerium sulfate, sodium saccharin, the two kinds of additives could improve cathodic polarization of the bath, and grain refinement of the nickel coating; they will change plane orientation of the nickel coating,but not make the(220) plane in preferential orientation; After addition of sodium saccharin and cerium sulfate, the nickel coating in the bath will make the corrosion tendency increases, and easy to produce chemical dissolution,it’s useless to be nickel anode.(3)In the electrolysis thick nickel process,It can effectively reduce the concentration polarization for loop filter, but can reduce quantity of wetting agent a bit, cause surface pitting of the nickel layer increases, affect the quality of the coating seriously. It canreduce current density around the nickel-starting sheet, eliminate production of nickel tumors for auxiliary cathode, but form a lot of nickel around it to increase the cost of production, and it’s not beneficial for actual production. It can reduce pinhole, pitting of nickel coating, at same time, it can effectively reduce the nickel tumors, and greatly improve the quality and productivity of electrolytic nickel.(4)Under different strain rate and deformation temperature, the constant strain rate isothermal compression tests were carried out on the electrolytic thick nickel.Experimental results show that after hot rolling of thick nickel,its microstructure is uniform and compact.The strain rate,stress variables and strain temperature on microstructure, crystal orientation, subgrain size, corrosion resistance and solubility properties of electrolytic thick nickel have influence.At variable rate is 1s-1,shape variables is 30% and the temperature is 1100℃,electrolytic thick nickel and foreign nickel have similar properties, orientation of crystal plane along(220) preferred, and they have very similar anodic dissolution process.