Study On Nickel Plating Process And Stabilizer In Tin Plating

Electroplating and electroless plating,as an important branch of surface engineering technology,are an important means of imparting corrosion resistance,abrasion resistance,decorativeness and special functionality to various metallic and non-metallic components.With the continuous development of science and technology,people have put forward higher requirements for the electroplating industry.The limit of impurities in nickel plating solution,the temperature of electroless nickel plating solution and the stability of methanesulfonic acid plating tin solution have become urgent problems to be solved.Therefore,this paper studies the influence of Co²⁺,Fe²⁺,Cr³⁺and Mn²⁺on the electroless nickel deposition process,successfully developed the medium-temperature and medium-phosphorus electroless nickel-phosphorus alloy process and explores the mechanism and electrochemical properties of different stabilizers in methanesulfonic acid plating tin solution.The specific findings are as follows:1.After adding Co²⁺,Fe²⁺,Cr³⁺and Mn²⁺into the bath,the current efficiency decreases with the increase of the metal impurity concentration,and the decreasing order of the current efficiency is Fe²⁺>Cr³⁺>Mn²⁺>Co²⁺.The reason for the decrease of the current efficiency of nickel electroplating was discussed by cathodic polarization curves and cyclic voltammetry with addition of 1.0 g/L Co²⁺,Fe²⁺,Cr³⁺,Mn²⁺.The upper limit of the four metal ions in the plating solution was obtained by SEM characterization of the deposite with different concentration of metal ions.The upper limit of the control of the concentration of Co²⁺,Cr³⁺and Fe²⁺was 0.1 g/L.The upper limit of the concentration of Mn²⁺0.6 g/L.Co²⁺,Fe²⁺,Cr³⁺changed the diffraction peak intensity of the nickel coating and the peak position of the diffraction peak,while Mn²⁺had little effect on the crystal structure of the coating.The ICP results show that metallic impurities enter the coating during electrodeposition of nickel and increase as the concentration of metal ions in the bath increases.When the concentration of metal impurities in the bath is the same,the order of the metal impurities in the coating is Mn²⁺<Cr³⁺<Fe²⁺<Co²⁺.2.The effects of pH,temperature,sodium sulfate,sodium hypophosphite,sodium citrate,triethanolamine and ammonia on electroless nickel plating rate and phosphorus content were investigated by single factor experiments,and by orthogonal experiment,choose sodium hypophosphite,sodium citrate,ammonia,triethanolamine four factors to further optimize the formula,the basic formula of medium-temperature and medium-phosphorus electroless nickel plating was determined.In order to further improve the plating speed,the effects of different accelerators propionic acid,succinic acid and glycine on the plating rate and phosphorus content were studied.The results showed that propionic acid not only increased the plating rate of electroless nickel plating,but also made the phosphorus content of the coating be in the range of medium phosphorus.Therefore,the most suitable accelerator for this formulation is propionic acid,the optimum content of 0.04 mol/L,which determines the optimum formulation and technological conditions of phosphorus electroless nickel plating.3.Natural oxidation experiment,thermal accelerated oxidation experiment and hydrogen peroxide accelerated oxidation experiments showed that the stabilizing effect of stabilizers was as follows:hydroquinone>catechol>ascorbic acid>resorcinol.Cyclic voltammetry curves revealed the relationship between the stability of the plating solution and the oxygen consumption mass ratio,self-reduction ability and electrochemical activity of the stabilizer.It can be seen from the chronopotentials,impedance spectra and SEM images that phenolic stabilizers can increase the cathodic polarization of the bath,refine the grains and improve the uniformity of the coating,while ascorbic acid has a depolarization effect on the deposition of tin.Hydroquinone,has good electrochemical reversibility in the methanesulfonic acid system and has good cycle stability and is an ideal stabilizer that can be recycled during electroplating.Cathodic polarization curves show that in addition to antioxidants,hydroquinone also has the role of brightener and leveler.The corrosion resistance of tin coatings with different concentrations of hydroquinone was tested by Tafel curve,the results show that when the hydroquinone concentration of 1.0 g/L,the corrosion resistance of the coating the best.