Chemical passivation method for improving corrosion performance of low-nickel alloy

Abstract

The invention belongs to the technical field of metal surface modification, and particularly relates to a chemical passivation method for improving the corrosion performance of a low-nickel alloy, which is characterized in that copper chloride and an alcohol solution with a certain concentration are used as a chemical passivation solution, and surface passivation treatment is completed under the conditions of certain passivation time and passivation temperature; and the passivation time is 30 minutes and 60 minutes. And the passivation temperature is controlled at 25 + / -1 DEG C. Compared with the prior art, the austenite high-nitrogen low-nickel alloy has the beneficial effects that the problem that nickel resources depend on import is solved, the corrosion resistance of the austenite high-nitrogen low-nickel alloy with the tensile strength reaching 700 MPa is greatly improved after passivation treatment, and the austenite high-nitrogen low-nickel alloy can be widely applied to various industrial production fields in China.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface modification, and particularly relates to a chemical passivation method for improving the corrosion resistance of low-nickel alloys. Background Art

[0002] Metal surface passivation treatment is a method that makes the metal surface transform into a state that is not easily oxidized through chemical or electrochemical methods, thereby delaying the metal corrosion rate. The main purpose of passivation treatment is to form a protective film on the metal surface. This protective film usually has a dense structure, can closely cover the metal surface, change its surface state, make its electrode potential jump in the positive direction, and show the corrosion-resistant noble metal properties.

[0003] Nickel-based alloys are one of the important key materials in the aviation field. Currently, more than 95% of aircraft landing gears, wing main beams, etc. are made of ultra-high-strength steel. Existing low-nickel alloys have poor corrosion resistance due to the reduction of nickel element, and must be subjected to certain surface treatments during actual use to improve corrosion resistance.

[0004] Nickel-iron alloy is an important alloy material and has wide applications in many fields. There are many types of nickel-iron alloys, which mainly depend on the ratio of nickel and iron and the types and contents of other added elements.

[0005] From the perspective of nickel content, common ones include low-nickel iron alloys, medium-nickel iron alloys, and high-nickel iron alloys. The nickel content in low-nickel iron alloys is relatively low, generally between 5% - 9% - 20%. This alloy has a low cost, certain strength and corrosion resistance, and is commonly used in the manufacture of building materials or ordinary mechanical components with not particularly high performance requirements. For example, in some simple building frame structures, low-nickel iron alloys can provide basic structural support.

[0006] The nickel content in medium-nickel iron alloys is approximately between 20% - 50%. Its performance is between that of low-nickel and high-nickel iron alloys, and has a good balance in terms of strength, corrosion resistance, and heat resistance. It can be seen in the manufacture of some components of automobile engines. Automobile engines need to work in high-temperature and high-pressure environments. Medium-nickel iron alloys can not only withstand certain pressures and temperatures but also ensure the normal operation of components.

[0007] High-nickel iron alloys are alloys with a nickel content exceeding 50%. This alloy has excellent corrosion resistance, heat resistance, and good mechanical properties. It is widely used in commercial fields such as chemical industry, ocean engineering, and aerospace. For example, in ocean engineering, the seawater has extremely strong corrosiveness, and high-nickel iron alloys can ensure the normal operation of various equipment and facilities in the corrosive marine environment.

[0008] Yu Baoning, Zhao Guanghui, Yang Duhang et al. in the paper "Research on Surface Modification of Ni-based Alloy by Electron Beam Cladding TiC Coating [J]." published in "Precision Forming Engineering", 2023, 15(08): 139-147, which states that by preparing a TiC coating with good performance, the surface performance of low-nickel alloy can be improved, but there are problems such as long electron beam time, low efficiency, and high cost. Electron beam surface modification process is not applicable to large-sized low-nickel alloy components such as aircraft landing gears and wing main beams.

[0009] The Chinese invention patent with the application number 202411179973.6 discloses a method for passivating the surface of cemented carbide button bits, including: ultrasonically cleaning the cemented carbide button bits with a neutral cleaning agent; performing steam degreasing on the cleaned cemented carbide button bits with an organic solvent; pickling the degreased cemented carbide button bits by soaking them in a sulfuric acid solution; performing surface activation treatment on the pickled cemented carbide button bits with a diluted fluoride solution; passivating the surface-activated cemented carbide button bits by soaking them in a chromium-containing passivation solution; soaking and rinsing the passivated cemented carbide button bits with deionized water; and drying after rinsing. Existing acid-based passivation materials generally have problems of low passivation efficiency and high cost. Summary of the Invention

[0010] The purpose of the present invention is to provide a chemical passivation method for improving the corrosion resistance of low-nickel alloys, overcoming the deficiencies of the prior art. For high-nitrogen low-nickel alloys with austenitic structure, the best passivation process parameters are obtained, the passivation treatment efficiency is improved, the production cost is reduced, and reliable technical support is provided for the popularization and application of austenitic high-nitrogen low-nickel alloys with a tensile strength of 700 MPa.

[0011] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0012] A chemical passivation method for improving the corrosion resistance of low-nickel alloys, and the specific operation steps are as follows:

[0013] 1) Pretreatment of samples: The samples are first degreased with acetone, then cleaned with an aqueous cleaning agent and deionized water respectively, and can maintain a water film for more than 30 s for standby;

[0014] 2) Preparation of passivation solution: Prepare a copper chloride + alcohol chemical passivation solution;

[0015] 3) Passivation treatment: At a temperature of 25±1°C, the passivation time is 30 min and 60 min, and a dense passivation film is formed on the surface of the samples.

[0016] The chemical composition of the said sample is as follows by weight percentage: Ni 45.0 wt%, Cr 25 wt%, Mn 7.0 wt%, Si 1.6 wt%, Mo 6 wt%, Cu 0.24 wt%, Co 0.81 wt%, N 0.60 wt%, Al 1.4 wt%, Ti 1.43 wt%, Nb 6 wt%, W 2.6 wt%, V 1.3 wt%, and the balance is Fe and unavoidable impurities.

[0017] The mixing ratios of the said copper chloride + alcohol chemical passivation solution are respectively: 35 g of CuCl2 + 100 ml of alcohol and 45 g of CuCl2 + 100 ml of alcohol.

[0018] Both the said copper chloride and alcohol are of analytical purity.

[0019] The size of the said sample is 100 mm × 50 mm × 2 mm.

[0020] The composition of the said passivation film is Cr2O3 + NiCr2O4.

[0021] The reaction principle of the chemical passivation process of the solution of the present invention is as follows: When elements such as nickel, chromium, and molybdenum in the low-nickel alloy come into contact with the CuCl2 solution, a series of complex chemical reactions will occur. First, the metal elements in the low-nickel alloy react with CuCl2 in a displacement reaction, and nickel displaces copper in CuCl2. The reaction equation is Ni + CuCl2 = NiCl2 + Cu. The chromium element in the low-nickel alloy is easily oxidized in the solution to form a dense oxide film, thus playing a role in passivation protection.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1) The problem of relying on imported nickel resources is solved. After the austenitic high-nitrogen low-nickel alloy with a tensile strength of 700 MPa is passivated, its corrosion resistance is greatly improved, enabling this material to be widely used in various production fields of our country's industry;

[0024] 2) The efficiency of the passivation process is increased by 50%. The original processing time was 30 minutes, and now the processing time is 15 minutes; the processing cost of the present invention is 500 yuan / ton, a reduction of 37.5%. Description of the Drawings

[0025] Figure 1 It is a comparison chart of the electrochemical conditions and corresponding results of the examples and comparative examples of the present invention. Detailed Embodiments

[0026] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention.

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the specific examples required for use in the description of the specific embodiments or the prior art. Obviously, the specific examples described below are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other specific examples can be obtained based on these specific examples.

[0028] Generally, the components of the embodiments of the present invention described and shown in the specific examples here can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific examples is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention.

[0029] For the sample materials in Examples 1-4 and the comparative example below, a new type of high-nitrogen and low-nickel alloy developed by Shenyang University of Technology is selected. Its chemical composition by mass percentage is: Ni 45.0wt%, Cr 25wt%, Mn 7.0wt%, Si 1.6wt%, Mo 6wt%, Cu 0.24wt%, Co 0.81wt%, N 0.60wt%, Al 1.4wt%, Ti 1.43wt%, Nb 6wt%, W 2.6wt%, V 1.3wt%, and the rest is Fe and unavoidable impurities. Before chemical passivation, the samples are first degreased with acetone, then washed with an aqueous cleaning agent and deionized water respectively, and can maintain a water film for more than 30 s for standby.

[0030] Example 1

[0031] 1) Pretreatment of the sample: The sample is first degreased with acetone, then washed with an aqueous cleaning agent and deionized water respectively, and can maintain a water film for more than 30 s for standby;

[0032] 2) Preparation of the passivation solution: Prepare a chemical passivation solution of 35 g CuCl2 + 100 ml alcohol;

[0033] 3) Passivation treatment: The sample is passivated at a temperature of 25 ± 1 °C for 30 min, and a dense passivation film is formed on the surface of the sample.

[0034] The composition of the passivation film of the sample in Example 1 is Cr2O3 + NiCr2O4. At this time, it can be seen from the XPS peak area data that Cr2O3 exists at this time, but the content of the Cr2O3 peak is small.

[0035] Example 2

[0036] 1) Pretreatment of the sample: First, degrease the sample with acetone, then clean it with an aqueous cleaning agent and deionized water respectively, and be able to maintain a water film for more than 30 s for standby;

[0037] 2) Preparation of the passivation solution: Prepare a chemical passivation solution of 35 g of CuCl2 + 100 ml of alcohol;

[0038] 3) Passivation treatment: At a temperature of 25 ± 1 °C, the passivation time is 60 min, and a dense passivation film is formed on the surface of the sample.

[0039] In Example 2, the composition of the passivation film on the sample is Cr2O3 + NiCr2O4. At this time, from the XPS peak area data, it can be seen that the area of the Cr2O3 peak is the largest, proving that the content of Cr2O3 is the highest at this time and the passivation effect is the best.

[0040] Example 3

[0041] 1) Pretreatment of the sample: First, degrease the sample with acetone, then clean it with an aqueous cleaning agent and deionized water respectively, and be able to maintain a water film for more than 30 s for standby;

[0042] 2) Preparation of the passivation solution: Prepare a chemical passivation solution of 45 g of CuCl2 + 100 ml of alcohol;

[0043] 3) Passivation treatment: At a temperature of 25 ± 1 °C, the passivation time is 30 min, and a dense passivation film is formed on the surface of the sample.

[0044] In Example 3, the composition of the passivation film on the sample is Cr2O3 + NiCr2O4. At this time, from the XPS peak area data, it can be seen that Cr2O3 exists at this time, but the content of the Cr2O3 peak is less.

[0045] Example 4

[0046] 1) Pretreatment of the sample: First, degrease the sample with acetone, then clean it with an aqueous cleaning agent and deionized water respectively, and be able to maintain a water film for more than 30 s for standby;

[0047] 2) Preparation of the passivation solution: Prepare a chemical passivation solution of 45 g of CuCl2 + 100 ml of alcohol;

[0048] 3) Passivation treatment: At a temperature of 25 ± 1 °C, the passivation time is 60 min, and a dense passivation film is formed on the surface of the sample.

[0049] In Example 4, the composition of the passivation film on the sample is Cr2O3 + NiCr2O4. At this time, from the XPS peak area data, it can be seen that Cr2O3 exists at this time, but the content of the Cr2O3 peak is less.

[0050] Comparative example

[0051] A high nitrogen low nickel alloy sample that has not been passivated is used as a comparative example, and the composition of the sample passivation film is NiCr2O4. From the XPS peak area data, it can be seen that there is no Cr2O3 passivation layer at this time. The self-corrosion potential and corrosion current density of the passivation film layer are detected by electrochemical polarization method as a comparison basis for the passivation process parameters of Examples 1-4.

[0052] After the chemical passivation of Examples 1-4 and the comparative samples was completed, the samples were blown dry with clean compressed air and set aside. The surface was polished to 2000# with water sandpaper step by step, then polished with diamond grinding paste, and finally ultrasonically cleaned in acetone and deionized water for 10 minutes, and dried in air for use. The sample size was 100mm×50mm×2mm.

[0053] The present invention adopts the electrochemical polarization method to detect the self-corrosion potential and corrosion current density of the passivation film layer as the basis for optimizing the passivation process parameters. The electrochemical polarization adopts the PARSTAT2273 electrochemical workstation, the test solution is a 3.5% NaCl solution, the polarization curve adopts a three-electrode system, in which the auxiliary electrode is a platinum electrode, the reference electrode is a saturated calomel electrode (SCE), and the area of ​​the sample immersed in the electrolyte is 1cm 2 At the same time, XPS was used to test the thickness of the passivation film.

[0054] The present invention tests the effects of different cupric chloride concentrations and different passivation times on the passivation degree of the high nitrogen low nickel alloy by using Examples 1-4 and Comparative Examples. The results are shown in Table 1.

[0055] Table 1 Electrochemical results of high nitrogen low nickel alloy after different passivation processes and bare material

[0056]

[0057] As can be seen from Table 1, after the passivation treatment of the present invention, the corrosion resistance of the high nitrogen low nickel alloy has been greatly improved. The electrochemical polarization curve comparison diagram of different passivation processes for high nitrogen low nickel alloy in 3.5% NaCl solution shows that different passivation processes have different polarization curves for high nitrogen low nickel alloy, indicating that they have different corrosion resistance, and each component has been passivated. The larger the passivation interval, the better the corrosion resistance of the material. Different passivation processes have different self-corrosion current density and self-corrosion potential. The self-corrosion current density is a kinetic criterion, which directly reflects the corrosion rate of the high nitrogen low nickel alloy, and the self-corrosion potential is a thermodynamic criterion, which directly reflects the corrosion trend.

[0058] As can be seen from Table 1, the self-corrosion potential of the high-nitrogen and low-nickel alloy under the process of 35 g of CuCl2 + 100 ml of alcohol + passivation time of 60 min in Example 2 is the largest, and the tendency to corrode is weak. This is because the passivation film structure is the most compact at this time, resulting in higher corrosion resistance. At the same time, this process is applicable to larger components such as aircraft landing gears and wing main beams, and the process is simple. The present invention reduces the nickel element content, resulting in a low cost of the high-nitrogen and low-nickel alloy powder. In addition, the passivation process cost of the nickel-based alloy is 500 yuan / ton, which is 37.5% lower than the previous 800 yuan / ton using acid passivation.

[0059] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A chemical passivation method for improving the corrosion performance of low nickel alloys, characterized in that: The specific steps are as follows: 1) Sample pretreatment: The sample is first degreased with acetone, then cleaned with aqueous detergent and deionized water, and the water film can be maintained for more than 30 seconds for standby use; 2) Preparation of passivation solution: prepare copper chloride + alcohol chemical passivation solution; 3) Passivation treatment: The sample is placed at a temperature of 25±1°C for 30 min and 60 min, and a dense passivation film is formed on the surface of the sample.

2. A chemical passivation method for improving the corrosion performance of low nickel alloys according to claim 1, characterized in that: The chemical composition of the sample is as follows by weight percentage: Ni 45.0wt%, Cr 25wt%, Mn 7.0wt%, Si1.6wt%, Mo 6wt%, Cu 0.24wt%, Co 0.81wt%, N 0.60wt%, Al 1.4wt%, Ti 1.43wt%, Nb6wt%, W 2.6wt%, V 1.3wt%, and the rest is Fe and unavoidable impurities.

3. A chemical passivation method for improving the corrosion performance of low nickel alloys according to claim 1, characterized in that: The proportions of the cupric chloride + alcohol chemical passivation solution are respectively: 35gCuCl2+100ml alcohol and 45gCuCl2+100ml alcohol.

4. A chemical passivation method for improving the corrosion performance of low nickel alloys according to claim 1, characterized in that: The cupric chloride and alcohol are both analytically pure.

5. A chemical passivation method for improving the corrosion performance of low nickel alloys according to claim 1, characterized in that: The sample size is 100 mm×50 mm×2 mm.

6. A chemical passivation method for improving the corrosion performance of low nickel alloys according to claim 1, characterized in that: The composition of the passivation film is Cr2O3+NiCr2O4.

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