The Research Of Environmentally Friendly Passivation Process On Carbon Steel Chemical Nickel Plating Layer

Chemical nickel plating endowed with special physical and chemical properties of materials and is widely used in chemical, aerospace, machinery, instrument, computer,and other fields.Without the passivation, cause plating layer of poor corrosion resistance or affecting the product quality and functional performancedirectly.Therefore, need passivation to chemical nickel plating layer.According to the principle of chemical nickel plating passivation process,systematically studied the carbon steel chemical nickel plating layer passivation process and optimization under the condition of do not chang chemical nickel plating pretreatment and plating process in this thesis.To get comparable to those of traditional chromium passivation in environmentally friendly low chromium passivation process,made a preliminary discussion about the corrosion resistance of passivating film,and the microstructure and element composition by porosity, nitrate color changing time, neutral salt spray test and electrochemical test, SEM and EDS.The main research contents and results:1.Carbon steel chemical nickel plating layer after passivation of the chromium content(potassium dichromate to 40 g/L) and low chromium(potassium dichromate content to 5 g/L) has played a very good hole sealing effect,the porosity compared with the specimens no passivation can significantly reduce 60% ~ 93% above the average and the latter than the former has better hole sealing effect.The optimization of process parameters of low chromium passivation for passivation temperature 70 ℃,10 min, passivation time passivation solution p H 2.0;The basis formula of the passivation liquid is heavy chromium acid potassium 5 g/L, ammonium fluosilicate0.5 g/L.2.Studied the influence of the inorganic additives such as ammonium molybdate and organic additives such asphytic acid introduced to the basic formula on thepassivation effects.The nitric acid resistant discoloration time of the ammonium molybdate,cerium nitrate, yttrium oxide, phytic acid, MEA and PAA compared with the basic formula can be extended 93%, 2.3% and 46%, respectively, 8.6%, 43% and0.8%.3.Optimization of inorganic additives, organic additives and inorganic-organic composite additives through the orthogonal test.The passivation effect is significant that adding ammonium molybdate 16 g/L yttrium oxide 4 mg/L, phytic acid 18 ml and MEA 35 ml in basic formula under the condition of the identified process,whose nitric acid resistant discoloration time compared with the basic formula after passivation can be extended about 2.6 times.4.Research the passivation film after optimized passivation process by porosity,nitrate color changing time, neutral salt spray test and electrochemical test, SEM and EDS.The results show that the salt spray corrosion resistance time can be extended by12 h, relative polarization resistance can be increased about one times compared with traditional chromium passivation,and the microstructure is most compact at the same time as reduce the chromate concentration significantly.