| Acid sulfate,pyrophosphate copper plating process can not meet the diversified requirements of the copper plating layer in the aviation industry because of its poor adhesion and high porosity.At present,aviation industry is still dominated by cyanide copper plating process in our country.While,the HEDP（1-hydroxyethane-1,1-diphosphonic acid）copper plating was widely concerned because of its good throwing power,high current efficiency and could be directly plated on steel surface.Aimed at the disadvantage of high porosity of copper plating layer,added additive A and B into HEDP copper plating solution.The cathode polarization,wettability,leveling effect of additive A and B were studied to ensure the appropriate concentration of additives.Added additive A and B and applied the cathode movement at the same time to decrease the porosity of copper plating layer.In addition,from the aspects of the plating solution and the properties of the coating,the HEDP copper plating process was compared with the cyanide copper plating process.The variation of content of Cu2+ and HEDP in the HEDP copper plating bath with power consumption was measured by titration method,the adjustment and maintenance according to the technological requirements.The effects of different passivation processes on the corrosion resistance of HEDP copper coating were compared by means of electrochemical tests,and the mechanism of improving the corrosion resistance of HEDP copper coating was discussed.The main results are as follows:Addition of 0.4 g/L additive A and 2 mg/L additive B,the adsorption effect of additive made the polarization potential to improve,inhibited the deposition of copper and refines the crystal grain.At the same time,additive A could reduce the surface tension and the interfacial free energy of the liquid solid,enhance the wetting ability of the solution to the cathode interface,which was conducive to the solution spreading on the surface of the sample,so as to effectively inhibit the hydrogen evolution reaction.When adding 0.4 g/L additive A and 2 mg/L additive B while applying cathode movement with 3 cm/s movement speed,the residence time of hydrogen bubbles on the surface of the sample was shortened,the hydrogen bubbles from the cathode could rapidly desorb,avoiding the formation of pinholes and pittings of the large size,the inner structure of the copper coating was continuous and compact.The thickness of the copper coating without no porosity was just 8 μm,at the same coating thickness,cyanide copper plating and other cyanide-free copper plating processes had higher porosity.The covering power,the throwing power of HEDP copper plating process hadreached or especially exceeded the level of cyanide copper plating process.Especially the cathodic current efficiency was much higher than that of cyanide copper plating process.When carburizing heat treatment,the thickness of the coating was about 15μm,the copper plating layer could effectively prevent the diffusion and penetration of carbon,which was obviously better than cyanide copper plating process.The basic reason was that the current efficiency was high,the copper coating had low porosity and good adhesion.What was more,after the HEDP copper plating process,the hydrogen embrittlement of 30 Cr Mn Si Ni2 A sample was qualified.The influence of HEDP copper plating process on the fatigue performance of 30 Cr Mn Si A sample was similar to that of cyanide copper plating process.For 1 L HEDP copper plating solution,the content of Cu2+was stable while the complexing agent HEDP would decrease because of hydrolysis reaction with the increase of the power consumption.The power consumption increased about 100 A·h,the content of HEDP in the plating solution needed to be adjusted and maintained.The plating solution had stable performance and convenient maintenance.Therefore,the environment friendly HEDP copper plating process could be used to replace the existing cyanide copper plating process.The corrosion resistance of copper plating layer was better than that of Cr（VI）passivation by using HAD chromium free passivation process,the improvement of the corrosion resistance was related to the increase of the density of the passive film and the improvement of the film structure. |
