Electrodeposition Mechanism Research Of Tungsten And Iron-group Metals In The Citric Acid And Ammonia Bath

The melting point of tungsten is the highest,compared to other metals.With the development of science and technology,tungsten and tungsten alloy are increasingly important and its application is also very extensive because of its hardness,corrosion resistance and abrasion resistance.Some researches on the electrodeposition of iron group and tungsten alloy and improving the proportion of tungsten in the alloy,can effectively improve and optimize the performance of iron-nickel-tungsten alloy,thereby promoting the development of electroplating industry and improving the level of human industrialization.In this paper,the mechanism of electrodeposition of iron group and tungsten alloy in citric acid-ammonia system is studied in detail,and the following conclusions are known:(1)Study the role of ammonia in nickel tungsten bathsFirst of all,in the citric acid bath,with ammonia as a basic environment,through the use of ultraviolet and cyclic voltammetry and other means can be infered:whether it is plating nickel bath or a separate tungsten bath,or nickel tungsten bath coexistence,as long as there is ammonia in the alkaline environment under the conditions of nickel bath,tungsten bath,nickel tungsten bath mixture formed by the composition will increase,and only in the ammonia bath,the electrodeposition The process of nickel tungsten bath Faraday current efficiency than at least twice the ammonia-free environment,which electrodeposited good performance of the nickel-tungsten alloy.The addition of ammonia can promote the formation of multi-core complexes.(2)Study of electrodeposition mechanism of nickel-tungsten alloy in citric acid-ammonia system:In the citric acid-ammonia bath,nickel and citric acid form Ni(Cit)(NH3)2-;tungstic acid and citric acid-ammonia form[WO2(Cit)]-complex;Ni and W coexist,nickel citric acid complex with tungsten citrate complex toform[Ni(WO2)(Cit)(NH3)2]+multinuclear mixed complex.Tungsten is only electrochemically active in the multicore confounding complex and its discharge mechanism is[Ni(WO2)(Cit)(NH3)2]++8e+2H2O→Ni+W+Cit3-+2NH3 ↑ +40H-If without the presence of Ni,W can not be restored.This mechanism can be a good explanation why in tungsten nickel coating,the tungsten content will not exceed 35%(3)Study on electrodeposition mechanism of Iron-tungsten alloy in citric acid-ammonia system:In the case of W-Fe alloy iron and citric acid form Fe(Cit)(NH3)-,tungstic acid and citric acid-ammonia form[WO2(Cit)]-complex with iron and citric acid in citric acid-ammonia system;[Fe(WO2)(Cit)(HH3)]+ multinuclear complexes were formed by the combination of iron citric acid complex and tungsten citrate complex.Tungsten has only electrochemical activity in the multi-core confounding complex,and its discharge mechanism is:[Fe(W02)(Cit)(NH3)]++8e+2H20→Fe+W+Cit3-+NH3↑+4OH-Without the presence of Fe,tungsten can not be restored.This mechanism can be a good explanation why in the tungsten iron coating,the tungsten content will not exceed 40%...