Study On The New Technology Of La/Ce Double Rare Earth Salts Passivation On The Surface Of Power Machinery Copper Alloy Workpiece

Copper alloys are widely used in chemical industry,electronics,power machinery and other fields because of their excellent properties.Due to their frequent occurrence of different degrees of corrosion in production,their service life will be affected.In order to improve the corrosion resistance of copper alloy workpieces,the surface is usually treated with corrosion protection.In this paper,the preparation and corrosion resistance of lanthanum and cerium double rare earth conversion coatings on the surface of H62 copper alloys were mainly studied.The optimum passivation solution formula containing La³⁺/Ce³⁺double rare earth salt was obtained through orthogonal test,and the La³⁺/Ce³⁺double rare earth conversion coating was formed on the surface of copper alloys by chemical immersion.Based on the scheme of passivation solution obtained by a single rare earth salt,the optimum passivation solution formulation of the double rare earth salt conversion film was determined by orthogonal test and single factor experiment.The corrosion resistance of rare earth conversion coating was evaluated by nitric acid spot test,salt spray test,constant temperature and humidity test and weightlessness test;And the corrosion behavior of passive film in sodium chloride solution and artificial seawater solution was also analyzed;Through electrochemical tests such as anodic polarization and AC impedance,the corrosion resistance of rare earth conversion coatings was further analyzed and discussed.Analyzing the surface morphology of rare earth passivation films by scanning electron microscope?SEM?;As well as using the X ray energy spectrometer?XRD?to analyze the composition of lanthanum cerium composite film and preliminarily discussed the corrosion resistance mechanism of rare earth conversion coating.The purpose of this project is to study the process flow of forming a stable,green,economical and environmentally friendly double rare earth conversion film on the surface of copper alloy,improve the mechanical corrosion resistance of copper alloy,provide better technical support for future research work,and lay the theoretical and technical foundation for practical production application.New process conditions of double rare earth:lanthanum nitrate-4g/L?Cerium nitrate-4g/L?Benzotr-iazole-15g/L?Sodium molybdate-3g/L?citric acid-14g/L?Sulfosalicylic acid-10g/L?sodium dodecyl benzene sulfonate-0.2g/L?Passivation temperature 50??Passivation time 5min.The double rare earth passivation solution obtained in this study can make the time of nitrate drop resistance of copper alloy up to 21.98 s,the time of salt tolerance of salt tolerance is sustainable 15 h,constant temperature constant is no obvious change in experimental 55 h,and the corrosion loss rates in 3.5%NaCl solution and artificial seawater solution are 0.3038 x(10^-2g/m²·h)and 0.4449 x(10^-2g/m²·h)respectively.The SEM results show that the double rare earth conversion coating is more smooth and uniform,with compact structure and strong adhesion with the substrate.The electrochemical test results showed that the synergistic effect of double rare earth salts reduced the corrosion current of the conversion coating,and increased the polarization resistance,and the corrosion resistance of the copper alloy increased significantly.XRD results showed that the main components of La/Ce double dilute conversion coating on brass surface are Cu₂O?CeO₂?La?OH?₃?Ce?OH?₄.