Design method for improving corrosion resistance of copper-nickel alloy by adding alloy elements

Abstract

The invention discloses a design method for improving corrosion resistance of a copper-nickel alloy by adding alloy elements. The design method comprises the following steps: screening the alloy elements; the first screening condition is that the solid solubility of the to-be-added alloy element in the copper-nickel alloy is larger than 0.1 wt.%, the second screening condition is that the standard electrode potential of the to-be-added alloy element is smaller than that of Ni, the third screening condition is that the deposition line of the to-be-added alloy element is lower than that of Cu2O, and the fourth screening condition is that the to-be-added alloy element is non-noble metal; based on the screening result, the mass percentage content range of the alloy elements is determined according to the maximum solid solubility of the alloy elements in the copper-nickel alloy; the ratio of the nucleation rate to the growth rate is larger than 104, and the corrosion rate is stabilized to be not higher than 0.02 [mu] m / a along with time, and the mass content of the alloy elements is obtained through optimization; and the final components and content of the added alloy element copper-nickel alloy are determined on the basis of the optimization result, and the corrosion resistance of the alloy element copper-nickel alloy is verified through experiments. The invention provides a design thought for the corrosion-resistant alloy with slowly dissolved main elements.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-nickel alloy materials, and in particular to a design method for improving the corrosion resistance of copper-nickel alloys by adding alloying elements. Background Art

[0002] Copper-nickel alloy has certain corrosion resistance, excellent thermal conductivity and mechanical ductility. As one of the most important marine engineering materials, it is widely used in pipeline engineering in seawater circulation systems, such as condensers, heat exchangers and seawater desalination equipment. However, in the face of highly corrosive marine corrosion environment, there is a high risk of failure after long-term service, so the corrosion resistance of copper-nickel alloy needs to be further improved. The corrosion resistance of copper-nickel alloy is generally attributed to the formation of a protective, internally dense and externally porous corrosion product film on the surface when exposed to seawater. Therefore, it is necessary to obtain a material with resistance to Cl - The corrosion product film is very important to improve the corrosion resistance of copper-nickel alloy.

[0003] Alloying is an effective method for improving the intrinsic corrosion resistance of alloys. Extensive research has shown that adding a range of alloying elements can improve corrosion resistance. However, the interactions between trace elements remain largely unknown. Consequently, the selection and addition of microalloying elements using alloying methods are still based on trial and error, lacking theoretical guidance. Furthermore, this trial and error method requires extensive effort, time, and material costs, making it difficult to achieve success the first time. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] To this end, the present invention provides a design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements, comprising the following steps:

[0006] Screening alloying elements; wherein, screening condition 1 is that the solid solubility of the alloying element to be added in the copper-nickel alloy is greater than 0.1 wt.%, screening condition 2 is that the standard electrode potential of the alloying element to be added is less than the standard electrode potential of Ni, screening condition 3 is that the deposition line of the alloying element to be added is lower than that of Cu2O, and screening condition 4 is that the alloying element to be added is a non-precious metal;

[0007] Based on the screening results, determining the mass percentage range of the alloying element according to the maximum solid solubility of the alloying element in the copper-nickel alloy;

[0008] Optimize the mass content of alloying elements; calculate the ratio of the nucleation rate to the growth rate of corrosion products and the evolution law of corrosion rate of copper-nickel alloys with added alloying elements, and use the ratio of the nucleation rate to the growth rate greater than 10 4The corrosion rate decreases steadily over time to no more than 0.02 μm / a as a dual criterion, and the mass content of the alloying elements is optimized;

[0009] Based on the optimization results, the final composition and content of the copper-nickel alloy with added alloying elements are determined, and its corrosion resistance is verified through experiments.

[0010] Furthermore, the screening of alloy elements includes:

[0011] The alloying elements suitable for addition are Fe, Mn and / or Cr.

[0012] Furthermore, the copper-nickel alloy is B30 copper-nickel alloy.

[0013] Furthermore, the determination of the mass percentage range of the alloying element according to the maximum solid solubility of the alloying element in the copper-nickel alloy includes:

[0014] According to the solid solubility of Fe in the copper-nickel alloy, the mass percentage range of Fe is determined to be 0.01% to 1.8%;

[0015] According to the solid solubility of Mn in the copper-nickel alloy, the mass percentage range is determined to be 0.01% to 2%;

[0016] According to the solid solubility of Cr in the copper-nickel alloy, its mass percentage content range is determined to be 0.01% to 2%.

[0017] Furthermore, the optimization of the mass content of alloying elements further includes:

[0018] First, the content of alloying element Fe in the ternary system Cu-Ni-Fe is optimized. Then, based on the optimized Fe content, the content of alloying element Mn in the quaternary system Cu-Ni-Fe-Mn and the content of alloying element Cr in the quaternary system Cu-Ni-Fe-Cr are optimized respectively.

[0019] In a feasible embodiment, based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, and the balance is Cu, and the corrosion rate is 0.033±0.002 mm / a.

[0020] In a feasible embodiment, based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Mn 0.5%, and the balance is Cu, and its corrosion rate is 0.032±0.002mm / a.

[0021] In a feasible embodiment, based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Cr 0.5%, and the balance is Cu, and its corrosion rate is 0.046±0.011 mm / a.

[0022] In a feasible embodiment, based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Mn 0.5%, Cr 0.5%, and the balance is Cu, and its corrosion rate is 0.042±0.001mm / a.

[0023] In a feasible embodiment, the method for preparing the copper-nickel alloy with added alloying elements comprises:

[0024] Weigh the raw materials according to the chemical composition percentage by mass of the copper-nickel alloy with added alloying elements;

[0025] placing the raw materials in a vacuum induction furnace for melting and casting to obtain a target alloy ingot;

[0026] The target alloy ingot is solution treated at 940-960°C for 15-18 hours.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] This invention improves the intrinsic corrosion resistance of copper-nickel alloys through alloying, providing a design strategy for corrosion-resistant alloys with slow dissolution of the main element. By microalloying Fe, Mn, and Cr, and taking advantage of the asynchronous dissolution between the microalloying elements and the main element Cu, the copper ion concentration at the metal / solution interface is increased, resulting in a greater deposition tendency. Furthermore, a step-by-step nucleation mechanism is used to make the formed corrosion product film denser, thereby improving the corrosion resistance of the copper-nickel alloy. Ultimately, the corrosion rate of the copper-nickel alloy after homogenization heat treatment is lower than that of commercial B30 alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a deposition phase diagram of oxides or hydroxides corresponding to each alloying element in the Cu-Ni-Fe-Mn-Cr alloy provided in an embodiment of the present invention.

[0030] Figure 2 This is the calculation result of the corrosion rate provided in Example 1 of the present invention.

[0031] Figure 3 The calculation results of the corrosion rate provided for Examples 2-3 of the present invention.

[0032] Figure 4 These are the corrosion rate test results of Examples 1-4 of the present invention and Comparative Examples 1-2.

[0033] Figure 5 The electrochemical impedance Nyquist diagrams of Examples 1-4 of the present invention and Comparative Examples 1-2 are shown.

[0034] Figure 6 The electrochemical impedance spectroscopy (Bode) diagrams of Examples 1-4 and Comparative Examples 1-2 are shown. DETAILED DESCRIPTION

[0035] In order to better understand the above technical solution, the technical solution of the present invention is described in detail below through specific embodiments.

[0036] The present invention provides a design method for improving the corrosion resistance of copper-nickel alloys by adding alloying elements. The design method for improving the corrosion resistance of B30 copper-nickel alloys by adding alloying elements comprises the following steps:

[0037] (1) Screening of alloying elements suitable for addition:

[0038] Screening condition 1: The solid solubility of the alloying element to be added in the B30 copper-nickel alloy is greater than 0.1 wt.%.

[0039] Screening condition two: the standard electrode potential of the alloying element to be added is less than the standard electrode potential of nickel (Ni).

[0040] Specifically, the standard electrode potentials are By comparing the size relationship of the standard electrode potential, the dissolution order of each alloy element is determined to be Mn>Cr>Fe>Ni>Cu.

[0041] It should be noted that, considering the standard electrode potential E of the element corresponding to the metal θ The more negative the value, the earlier the metal dissolves. Therefore, the dissolution order of the alloy elements is determined by the standard electrode potential of each alloy element.

[0042] Screening condition three: The deposition line of the alloying element to be added is lower than that of Cu2O, and the deposition line is preferably much lower than that of Cu2O.

[0043] See also Figure 1 , through the solubility product constant K of each oxide and hydroxide sp , The critical deposition lines of oxides and hydroxides were calculated. Based on the idea that the lower the critical deposition line, the easier it is to deposit as corrosion products in this form, the deposition order of each alloying element was determined to be Fe>Cr>Mn>Cu>Ni.

[0044] Considering the solubility product constant K of the corresponding oxide or hydroxide of the element sp , the critical deposition criterion line of the element ion can be calculated. The lower the critical deposition line, the greater the deposition tendency. Therefore, the solubility product constant K of the oxide or hydroxide corresponding to each element can be calculated. sp , and then use the corresponding critical deposition criterion line to determine the deposition order of alloying elements.

[0045] The present invention takes into account that the speed of alloy element dissolution can be judged according to the standard electrode potential, and the deposition order of corrosion products can be reflected according to the critical deposition line of corrosion products. Therefore, according to the dissolution order of atoms corresponding to each alloy element and the deposition order of corresponding corrosion products, the alloy elements can be screened by taking the alloy elements that meet the requirements of both the dissolution order and the deposition order as screening conditions, thereby achieving the screening of alloy elements. The obtained high-corrosion-resistant copper-nickel alloy can quickly form a dense corrosion product film, thereby improving the corrosion resistance of the alloy.

[0046] Fe, Mn and Cr are selected as alloying elements. The asynchrony of dissolution and deposition between Fe, Mn and Cr and the main alloying element Cu is utilized, and a step-by-step amplification nucleation mechanism is used to make the corrosion product film denser, thereby improving the corrosion resistance of the alloy.

[0047] Screening condition four: Consider economic factors, control industrial production costs, and exclude precious metals.

[0048] Through screening, the alloying elements suitable for addition that meet the above four conditions are Fe, Mn and Cr, with Fe being the first choice.

[0049] (2) Based on the screening results, the mass percentage range of the alloying elements suitable for addition is determined according to the maximum solid solubility of the alloying elements in the B30 copper-nickel alloy. Specifically, the mass percentage range is: Fe 0.01% to 1.8%, Mn 0.01% to 2%, and Cr 0.01% to 2%.

[0050] (3) Optimize the mass content of alloying elements: Calculate the ratio of the nucleation rate to the growth rate of the corrosion products of the copper-nickel alloy with the addition of alloying elements and the evolution law of the corrosion rate, and take the nucleation rate as the maximum value (the ratio of the nucleation rate to the growth rate is greater than 10). 4 ) and the corrosion rate decreases to a stable low value over time (stable to no more than 0.02μm / a) as the dual criteria, and the mass content of the alloying elements is optimized.

[0051] Specifically, the equilibrium potential of each alloying element is first calculated based on the Nernst equation, and then the corrosion potential of the alloy is calculated based on the mixed potential theory. The dissolution current density of each alloying element is calculated and corrected based on the Butler-Volmer formula and the dissolution-blocking model. The ion concentration of each alloying element at the metal / solution interface is calculated based on Faraday's law and Fick's second law. The supersaturation S of each corrosion product is calculated using the ion concentration of each alloying element and the solubility product of the corresponding hydroxide and oxide of the alloying element as input. The nucleation rate and growth rate of the corresponding corrosion product are then obtained using crystal growth theory. Using the nucleation rate and growth rate of the corrosion product as input, the corresponding corrosion product coverage and the overall corrosion rate of the copper-nickel alloy are calculated.

[0052] The optimal mass content of the alloying elements is determined by taking the nucleation rate of the corrosion products as much greater than the corresponding growth rate and having the lowest corrosion rate as the optimal conditions.

[0053] The specific steps to optimize the mass content of alloying elements are as follows:

[0054] 1) The standard electrode potential corresponding to the alloying elements of the high corrosion-resistant copper-nickel alloy is used as input, and the equilibrium potential of the metal electrode reaction corresponding to each alloying element is calculated according to the Nernst equation (Equation (1)).

[0055]

[0056] In formula (1), E e is the equilibrium potential of the metal electrode reaction corresponding to each alloy element; E θ is the standard electrode potential corresponding to each alloying element; R is the gas constant; T is the temperature; [O] is the concentration of the oxidized substance; [R] is the concentration of the reduced substance; n is the number of transferred electrons; and F is the Faraday constant.

[0057] Then, the equilibrium potential of the metal electrode reaction corresponding to each alloying element is used as input to calculate the corrosion potential of the copper-nickel alloy according to the mixed potential theory. The anodic Tafel diagram or cathodic Tafel diagram of each alloying element is added together to obtain the anodic Tafel diagram of the alloy. a (E) or cathode Tafel diagram i c (E), the intersection of the anodic Tafel diagram and the cathodic Tafel diagram, is the corrosion potential E of the alloy. corr .

[0058] Then, the corrosion potential of the copper-nickel alloy is used as input, and the current density of each alloying element in the copper-nickel alloy under the corrosion potential is calculated according to the Butler-Volmer formula. Considering the mutual dependence of the dissolution of each alloying element in the solid solution alloy, the dissolution current density is corrected by the dissolution-blocking concept (Equation (2)):

[0059]

[0060] In formula (2), J M is the dissolution current density of each alloy element; f n is the atomic fraction of each alloying element; L M is the number of dissolved equivalent layers; i M is the current density of each alloying element; n is the number of transferred electrons.

[0061] 2) Using the dissolution current density corresponding to each element as input, the ion concentration and pH value at the interface are calculated according to Faraday's law and Fick's second law. Using the corresponding ion concentration of each alloying element and the solubility product constant of the corresponding oxide and hydroxide as input, the supersaturation σ of each corrosion product is calculated. The formulas involved in the calculation are shown in Equations (3) to (5):

[0062]

[0063]

[0064]

[0065] In formula (3), C dissolution is the cation dissolution flux; A is the metal area; J is the current density of the alloying element, n is the charge number of the ion; F is the Faraday constant; V is the boundary layer volume (V = 10 -4 m 3 ).

[0066] In formula (4), C diffusion is the diffusion flux; C is the boundary layer cation concentration; D is the diffusion coefficient; and t is time. The ion concentration at the interface is equal to the difference between anodic dissolution and diffusion.

[0067] In formula (5), σ is the supersaturation of corrosion products; C M n+ is the metal cation concentration; C N m- is the anion concentration; K sp is the solubility product constant of corrosion products.

[0068] Taking the supersaturation σ of each corrosion product as input, the nucleation rate and growth rate of the corresponding corrosion product are calculated by crystal growth theory. After the corrosion products continuously nucleate and grow, they are deposited on the alloy surface and gradually cover it completely. The ratio of the corrosion product coverage area to the alloy surface area is the coverage rate. Taking the nucleation rate and growth rate of the corrosion product as input, the coverage rate of the corrosion product is calculated. The alloy surface covered by the corrosion product has a different current density than the exposed alloy substrate surface. The overall corrosion current density of the alloy is obtained by adding the proportion of the alloy dissolution current density corresponding to the uncovered surface and the proportion of the corrosion product current density corresponding to the covered surface. As the corrosion products gradually cover the alloy surface, the overall corrosion rate of the copper-nickel alloy also decreases. The formula involved in the calculation is shown in formula (6):

[0069]

[0070] In formula (6), CR is the corrosion rate of the alloy; i corr is the corrosion current density of the copper-nickel alloy; M is the molar mass of the alloy; ρ is the density of the alloy; n is the number of transferred electrons; F is the Faraday constant; and t is time.

[0071] (4) Determine the final composition content of the copper-nickel alloy based on the optimized conditions.

[0072] Through the above optimization, the chemical composition of the high corrosion-resistant copper-nickel alloy obtained is as follows:

[0073] The chemical composition of the ternary alloy system is as follows: Ni 30%, Fe 0.6%, Cu 69.4%. Among them, the Fe content was optimized, and the initial corrosion rate and the final corrosion rate were reduced to a low level. The Fe content of 0.6% was selected. The results are as follows Figure 2 As shown, from Figure 2 It can be seen from the graph that as the Fe content increases from 0.1wt.% to 1.8wt.%, the initial corrosion rate decreases, while the time required for the final corrosion rate to reach a stable low level is longer.

[0074] The chemical composition of the quaternary alloy system is as follows: Ni 30%, Fe 0.6%, Mn 0.5%, Cu68.9% by mass; or, the chemical composition is as follows: Ni 30%, Fe 0.6%, Cr 0.5%, Cu68.9% by mass. Among them, the mass percentage of Mn was optimized, and the initial corrosion rate and the final corrosion rate were reduced to a lower level. The Mn content of 0.5% was selected. The mass percentage of Cr was optimized, and the initial corrosion rate and the final corrosion rate were reduced to a lower level. The results are as follows Figure 3 As shown, from Figure 3It can be seen from the graph that the alloy with a Mn content of 0.5 wt.% and a Cr content of 0.5 wt.% has the lowest corrosion rate level at the same time.

[0075] The five-element alloy system has the following chemical compositions by mass percentage: Ni 30%, Fe 0.6%, Mn 0.5%, Cr0.5%, and Cu 68.4%.

[0076] Example 1

[0077] (1) Composition of copper-nickel alloy: The chemical composition by mass percentage is: Ni 30%, Fe 0.6%, Cu 69.4%.

[0078] (2) The preparation method comprises the following steps:

[0079] (1) Weigh the raw materials according to the chemical composition mass percentage of the copper-nickel alloy.

[0080] (2) placing the raw materials in a vacuum induction furnace for melting and casting to obtain a target alloy ingot;

[0081] (3) The target alloy ingot is subjected to homogenization heat treatment at a temperature of 950° C. and a solid solution treatment time of 16 h to obtain a copper-nickel alloy.

[0082] Example 2

[0083] (1) Composition of copper-nickel alloy: The chemical composition by mass percentage is: Ni 30%, Fe 0.6%, Mn 0.5%, Cu 68.9%.

[0084] (2) Preparation method: Same as Example 1.

[0085] Example 3

[0086] (1) Composition of copper-nickel alloy: The chemical composition by mass percentage is: Ni 30%, Fe 0.6%, Cr 0.5%, Cu 68.9%.

[0087] (2) Preparation method: Same as Example 1.

[0088] Example 4

[0089] (1) Composition of copper-nickel alloy: The chemical composition by mass percentage is: Ni 30%, Fe 0.6%, Mn 0.5%, Cr 0.5%, Cu 68.4%.

[0090] (2) Preparation method: Same as Example 1.

[0091] Comparative Example 1

[0092] Comparative Example 1 uses commercial B30 copper-nickel alloy as the control group.

[0093] Comparative Example 2

[0094] (1) Composition of copper-nickel alloy: The chemical composition by mass percentage is: Ni 30%, Cu 70%.

[0095] (2) Preparation method: Same as Example 1.

[0096] Results and Discussion

[0097] The alloy samples were processed by wire cutting into specimens with a size of 10 mm × 10 mm × 5 mm. The sample surfaces were polished with 240#, 600#, 1000# and 2000# silicon carbide sandpapers in sequence until the scratches were consistent. The sample surfaces were cleaned with anhydrous ethanol and deionized water and then dried before being used for weight loss test and electrochemical test.

[0098] (1) Weightlessness test

[0099] According to GB / T 16545-2015 "Corrosion of Metals and Alloys - Removal of Corrosion Products on Corrosion Test Specimens", weight loss tests were conducted on Examples 1-4 and Comparative Examples 1-2. The test results are as follows: Figure 4 As shown. Figure 4 It can be seen that the corrosion rates of Examples 1-4 are all lower than those of Comparative Example 1 and Comparative Example 2, and Example 2 has the lowest corrosion rate; among them, the corrosion rate of Example 1 is 0.033±0.002mm / a, the corrosion rate of Example 2 is 0.032±0.002mm / a, the corrosion rate of Example 3 is 0.046±0.011mm / a, and the corrosion rate of Example 4 is 0.042±0.001mm / a.

[0100] In the Cu-Ni-Fe-Mn alloy system of Example 2 obtained according to the design method of the present invention, the micro-alloying elements Fe and Mn and the high-alloying element Ni are synergistically dissolved, the main element copper is dissolved last, and then the corrosion products of Fe are preferentially deposited, thereby transforming the corrosion products of Mn from homogeneous nucleation to heterogeneous nucleation, reducing its surface nucleation energy by 2 / 3 and promoting its deposition. Subsequently, the nucleation rate of Cu2O is further amplified by the corrosion products of Mn, and finally a dense protective film with a double-layer structure is formed on the alloy surface, thereby improving the corrosion resistance of the alloy.

[0101] (2) Electrochemical testing

[0102] The electrochemical workstation was used to perform AC impedance tests on Examples 1-4 and Comparative Examples 1-2. The results are as follows: Figure 5 and 6 . Example |Z| 0.01HzBoth are greater than the comparative example, indicating that the high corrosion-resistant copper-nickel alloy designed by the embodiment of the present invention has more excellent corrosion resistance.

[0103] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application. The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application. These improvements and variations should also be regarded as the scope of protection of the present application.

Claims

1. A design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements, characterized in that: The steps include: Screening alloying elements; wherein, screening condition 1 is that the solid solubility of the alloying element to be added in the copper-nickel alloy is greater than 0.1 wt.%, screening condition 2 is that the standard electrode potential of the alloying element to be added is less than the standard electrode potential of Ni, screening condition 3 is that the deposition line of the alloying element to be added is lower than that of Cu2O, and screening condition 4 is that the alloying element to be added is a non-precious metal; Based on the screening results, determining the mass percentage range of the alloying element according to the maximum solid solubility of the alloying element in the copper-nickel alloy; Optimize the mass content of alloying elements; calculate the ratio of the nucleation rate to the growth rate of corrosion products and the evolution law of corrosion rate of copper-nickel alloys with added alloying elements, and use the ratio of the nucleation rate to the growth rate greater than 10 4 The corrosion rate decreases steadily over time to no more than 0.02 μm / a as a dual criterion, and the mass content of the alloying elements is optimized; Based on the optimization results, the final composition and content of the copper-nickel alloy with added alloying elements are determined, and its corrosion resistance is verified through experiments.

2. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 1, characterized in that: The screening of alloying elements includes: The alloying elements suitable for addition are Fe, Mn and / or Cr.

3. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 2, characterized in that: The copper-nickel alloy is B30 copper-nickel alloy.

4. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 3, characterized in that: Determining the mass percentage range of the alloying element according to the maximum solid solubility of the alloying element in the copper-nickel alloy includes: According to the solid solubility of Fe in the copper-nickel alloy, the mass percentage range of Fe is determined to be 0.01% to 1.8%; According to the solid solubility of Mn in the copper-nickel alloy, the mass percentage range is determined to be 0.01% to 2%; According to the solid solubility of Cr in the copper-nickel alloy, its mass percentage content range is determined to be 0.01% to 2%.

5. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 4, characterized in that: The optimization of the mass content of alloying elements also includes: First, the content of alloying element Fe in the ternary system Cu-Ni-Fe is optimized. Then, based on the optimized Fe content, the content of alloying element Mn in the quaternary system Cu-Ni-Fe-Mn and the content of alloying element Cr in the quaternary system Cu-Ni-Fe-Cr are optimized respectively.

6. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 4, characterized in that: Based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be 30% Ni, 0.6% Fe, and the balance is Cu, and the corrosion rate is 0.033±0.002 mm / a.

7. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 4, characterized in that: Based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Mn 0.5%, and the balance is Cu, and its corrosion rate is 0.032±0.002 mm / a.

8. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 4, characterized in that: Based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Cr 0.5%, and the balance is Cu, and the corrosion rate is 0.046±0.011 mm / a.

9. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to claim 4, characterized in that: Based on the optimization results, the final composition of the copper-nickel alloy with added alloying elements is determined to be: Ni 30%, Fe 0.6%, Mn 0.5%, Cr 0.5%, and the balance is Cu, and its corrosion rate is 0.042±0.001 mm / a.

10. The design method for improving the corrosion resistance of copper-nickel alloy by adding alloying elements according to any one of claims 6 to 9, characterized in that: The method for preparing the copper-nickel alloy with added alloying elements comprises: Weighing raw materials according to the chemical composition percentage by mass of the copper-nickel alloy with added alloying elements; placing the raw materials in a vacuum induction furnace for melting and casting to obtain a target alloy ingot; The target alloy ingot is solution treated at 940-960°C for 15-18 hours.

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