| Copper-nickel alloys are widely used in various fields due to their good corrosion resistance,excellent processability,and excellent thermal conductivity,such as seawater pipelines,desalination plants,power plants,and heat exchangers and condensers in hulls.The main reason for the corrosion resistance of copper-nickel alloys is the formation of a passivation film on its surface.This protective film can serve as a corrosion barrier between the aggressive ions in the environmental medium and the substrate,which slows the corrosion of the substrate.At present,the rapid development of marine engineering has put forward higher requirements for the corrosion resistance of copper-nickel alloys,and it is still the goal of current research that the corrosion resistance of copper-nickel alloys should be further improved.Adding alloying elements is the most direct and effective method to improve the corrosion resistance of white copper alloy.Fe and Mn elements are the most common alloy elements in copper-nickel alloys.They can not only improve the mechanical properties of copper-nickel alloys but improve the corrosion resistance of copper-nickel alloys.The passivation film formed on the surface of white copper is a key factor affecting its corrosion performance.However,so far,there is relatively little research toward the influence of Fe and Mn alloy elements on the passivation film on the surface of white copper alloy.Rare earth elements have the reputation of"vitamins"in the metallurgical industry,which are considered to be able to further optimize the performance of the alloy.There are few reports on the effects of elements on the corrosion resistance of copper-nickel alloys.Based on the above reasons,B10 white copper alloys with different contents of Fe,Mn,and La were prepared in this paper,and the influence of the addition of these three alloying elements on the electrochemical corrosion performance of B10 white copper alloy samples was studied using polarization curve and AC impedance spectroscopy.According to the analysis results of X-ray diffractometer,X-ray photoelectron spectrometer,scanning electron microscope and other analysis and detection instruments,the influence mechanism of alloy elements Fe,Mn,La on the corrosion resistance of B10 copper-nickel alloy was discussed.?1?Adding Fe element is beneficial to improve the passivation performance of B10 white copper alloy in sodium borate buffer solution?pH=9.0?.The addition of Fe reduces the dimensional passive current density of B10 alloy,increasing the passivation interval of the alloy in the presence of Cl-and the pitting potential.Meanwhile,it also reduces the secondary passivation current density.When the Fe element content is 1.5wt.%,the B10 alloy has the best corrosion resistance,the largest pitting potential(0.62VSCE),and the lowest secondary passivation current density which is about25.11?A/cm250.12?A/cm2.?2?Fe mainly exists in the form of FeOOH and FeO in the passivation film on the surface of B10 white copper.The increase of NiO and FeOOH is beneficial to enhance the corrosion resistance of the alloy surface film.The addition of Fe element has an important impact on the semiconductor performance of B10 copper-nickel alloy.As the Fe content increases,the carrier?cation vacancy?density and diffusion coefficient in the passivation film decrease first and then increase later.When the Fe content is 1.5 wt.%,the carrier density and cation diffusion coefficient in the passivation film are the smallest,which is also the reason why it has the best passivation performance and pitting corrosion resistance.?3?Adding Mn element is beneficial to improve the passivation performance of B10 white copper alloy in sodium borate buffer solution?pH=9.0?.The alloy samples added with Mn element have lower corrosion rate and smaller dimensional passive current density.With the increase of Mn content,the pitting potential of B10 white copper alloy increased first and then tended to remain unchanged,while the secondary passivation current density decreased first and then increased later.When the Mn content is 0.8wt.%,the carrier density and cation diffusion coefficient in the alloy passivation film are the smallest,which greatly reduces the probability of cation vacancies and aggressive ions in the passivation film,and improves the pitting potential.?4?Rare earth La can improve the corrosion resistance of B10 alloy in 3.5 wt.%NaCl solution.With the immersion time extended to 30 days,the effect of rare earth to improve the corrosion resistance gradually increased.With the increase of rare earth content,the corrosion resistance of the alloy showed a tendency that increases firstly and then decreases later.When the content of rare earth La was 0.063wt%,the corrosion resistance was the best.Rare earth La can effectively improve the bonding force and stability between the corrosion product film on the surface of B10 alloy and the substrate,and also,reduce the cracks in the corrosion products.XPS results show that the B10 alloy corrosion product film added with rare earth La has a higher Ni content and at the same time,the corrosion product film is doped with rare earth oxide La2O3.La2O3 improves the corrosion resistance of B10 white copper alloy by inhibiting the cathode reaction and enhancing the dielectric properties of the surface film. |
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