Study On Technics Of Electroless Thick Nickel And Its Mechanism

The coating of besides have the features of high thickness except for good performance as well as general thickness of electroless nickel deposits(20μm～50μm). In the aviation industry and chemical industry, the application have become more and more important, Especially in the aero-engine repair parts and other expensive areas, electroless thick nickel is widely used. In the process of electroless thick nickel, coating deposition rate and solution stability are the key that electroless thick nickel can be achieved, it's also the difficulty of study. Therefore, this article test palladium chloride and measurement of stability constants, research and analysis the influence of various components of the bath concentration and operating conditions on the plating rate, bath stability and coating quality. Optimize the best technology of electroless thick nickel. In order to maintain long-term nature of the bath, this article also research the additional ways for the bath. Monitor the composition of chemical bath with EDTA omplexometric titration, and carries on the orthogonal experiment based on the consumed amount of active ingredient in the bath, Finally determines the best increase way.The results show that, various components of bath concentration and operating conditions can affect the plating rate and bath stability, the most important factor is the complexing agent, stabilizer, temperature and pH value. At the same time, in the process of electroless thick nickel, adding method on the life of bath plays a vital role.This paper studies the best craft is:25g/L NiSO4·6H2O; 25 g/L NaH2PO4; 30 g/LC6H5Na3O7; 30 g/L (NH4)2SO4; 1mg/L Stabilizer; pH=9; temperature 90℃; examine the bath every one hour, and carries on the supplement.Examine the plating by scanning electron microscopy (SEM), observes the surface morphology of coatings compact and uniform, coating and matrix substrate very well. Measured phosphorus content of 9.38% by the spectrum analyzer (EDS), equivalent to the level of phosphorus in electroless nickel plating, and each layer has stable of content, can significantly improve the corrosion resistance of the matrix. After heat treatment on 400℃, the hardness of coating can reach to 1120HV. The porosity of the coating is almost 0, improve the corrosion resistance of the coating. The corrosion experiments confirmed that corrosion resistance of coatings in a variety of media are very good.