The Preparation And Technological Study Of Nicotinic Acid Double-pulse Non-cyanide Silver Plating

With the development of materials science and technology, silver has steady physical and chemical performance, it was applied in fields of electric,optical,catalytic. As a cyanide silver electroplating have highly toxic, serious pollution of the environment, endanger the health of producers and other shortcomings, Non-cyanide silver plating is increasingly becoming the focus of scientific research workers. This article study on Nicotinic acid silver plating conditions, aim to get bright and delicate crystal coating, therefore further promote the development of Non-cyanide silver plating.In order to observe the silver crystalline growth state, This article choose amorphous Ni-P coating and the NAS 185N stainless steel for the basement, the amorphous Ni-P coating electrolyte composition and operating conditions were:Nickel sulfate 240g/L, Nickel chloride 20g/L, Sodium citrate 72.8g/L, Phosphite 30g/L, Current density 0.1A/dm2,pH value 2,Temperature 70℃, Positive duty cycle 20%, Reverse duty cycle 10%,Working Hours 15min ,the XRD analysis showed that the obtained Ni-P coating is amorphous coating.In the present work, nicotinic acid non-cyanide silver electrod-eposition bath was chosen as the research bath to avoid defect of other systems. Based on the single factors study, the optimal composition formula was obtained by an orthogonal method. And with the optimal formula, the influence of bath composition and operating conditions on the properties of solution and coatings was studied. And the result showed the optimal electrolyte composition and operating conditions were: silver nitrate 20g/L, nicotinic acid 70g/L, potassium carbonate 50g/L, duty cycle 40%, pH value 10, And to determine the appropriate combination of additive dosage 40ml / L. Temperature 25℃, Frequency 1000Hz, Current density 0.25A/dm2, Cathode-anode area ratio 1:1, anode shape silver plate. The result of test is that the coating has good adhesion strength, bright and anti- tarnish property. Comparing with the other experimental results, the silver layer using the double-pulse technique in the same process condition has more excellent performance.The XRD result shows that the preferential orientations of silver coating is (111) and (220) ,but the coating in butanedimide system is (111).Compared and analyzed the Silver Standard map, both systems have Four distinct peaks: 38.2°,44.4°,64.54°,77.5°, Correspond to the cubic crystal silver (111), (200), (220), (311) plane, Cubic crystal system was obtained. And compared with the different basement through SEM, the silver plating on the NAS 185N stainless steel is brighter, more smooth and with sizable crystals. The result achieves the expected aim of the experiment.