Method for preparing lattice-type passivation corrosion-resistant film on metal surface

Abstract

The present invention belongs to the technical field of metal surface treatment and relates to a method for preparing a lattice-type passivation corrosion-resistant film on a metal surface. The method comprises the following steps: after polishing and cleaning the metal surface, constructing a three-electrode system, applying a cathode voltage to the metal to perform surface modification treatment, thereby reconstructing the metal surface lattice and forming a dense adsorption layer of corrosion-inhibiting molecules; the three-electrode system comprises: a metal as a working electrode, a platinum sheet as an auxiliary electrode, and silver / silver chloride or saturated calomel as a reference electrode. The method of the present invention utilizes cathode voltage treatment to reconstruct the metal surface lattice, overturning the technical approach of traditional anodic oxidation. This method enables the passivation film to form a regular lattice structure, significantly reducing defects within the film, effectively blocking the penetration of corrosive media, and significantly improving the metal's corrosion resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment and relates to a method for preparing a corrosion-resistant passivation film on a metal surface. Background Art

[0002] Metal corrosion not only causes huge economic losses but also poses a serious threat to safety and the environment. A passivation film formed on the metal surface can isolate the metal from external corrosive media, effectively inhibiting corrosion and extending the service life of metal structures.

[0003] Traditional metal passivation films are primarily formed through the following methods: oxidation in air under natural conditions; treatment in chemical environments (such as nitric acid or chromate solutions); and electrochemical anodic oxidation. However, electrochemical modification results in a non-uniform crystalline or amorphous structure of the oxide within the passivation film. This results in numerous defects within the film and abundant ion channels, allowing corrosive media (such as chloride and oxygen ions) to easily penetrate the film and reach the metal substrate. This makes long-term protection difficult in demanding environments requiring high corrosion resistance.

[0004] Furthermore, existing cathodic protection technology involves connecting metal to the cathode of a potentiostat and applying a high voltage. This continuous electron output from the cathode can inhibit corrosion of metal structures. However, this method does not improve the corrosion resistance of the passive film on the metal surface itself. Furthermore, the technology requires continuous power supply, resulting in high electricity costs for long-term operation. Furthermore, the generation of hydrogen on the steel surface can easily cause hydrogen embrittlement, compromising the safety of the metal structure. Furthermore, cathodic protection does not improve the performance of the passive film itself; once the power is lost, the metal structure loses its protection.

[0005] Therefore, there is an urgent need to develop a method for preparing a passivation film that can form a highly regular, defect-free, and corrosion-resistant passivation film on the metal surface, so as to improve the corrosion resistance of metal materials in harsh environments, extend their service life, and reduce maintenance costs. Summary of the Invention

[0006] Based on the above background, the present invention provides a method for preparing a lattice-type passivation film on a metal surface, addressing the numerous defects and insufficient corrosion resistance of conventional passivation films described in the prior art. By applying a cathode voltage, the present invention reconstructs the metal surface lattice, and corrosion-inhibiting molecules in the electrolyte form a dense adsorption layer through molecular adsorption. The resulting ultra-high corrosion-resistant metal passivation film significantly improves the metal's corrosion resistance.

[0007] The present invention provides the following technical solutions:

[0008] A method for preparing a corrosion-resistant passivation film on a metal surface comprises the following steps:

[0009] After the metal surface is polished and cleaned, a three-electrode system is constructed and a cathode voltage is applied to the metal to perform surface modification treatment, thereby achieving lattice reconstruction on the metal surface and forming a dense adsorption layer of corrosion-inhibiting molecules.

[0010] The three-electrode system includes: metal as a working electrode, a platinum sheet as an auxiliary electrode, and silver / silver chloride or saturated calomel as a reference electrode.

[0011] Furthermore, the cathode voltage of the three-electrode system is -0.8 to -1.5 V, and the power-on time is 12 to 20 hours.

[0012] Furthermore, the metal is iron or nickel.

[0013] Furthermore, the polishing and cleaning of the metal surface includes: polishing the metal surface with sandpaper of different mesh sizes in sequence, then rinsing the surface with deionized water and ethanol, cleaning with ethanol in an ultrasonic cleaner to remove surface impurities, and finally drying with hot air.

[0014] Furthermore, the cleaning time with ethanol in the ultrasonic cleaner is 2 to 4 minutes.

[0015] Furthermore, the surface-modified metal was washed with deionized water and ethanol, respectively, and then dried with hot air.

[0016] Furthermore, the electrolyte of the three-electrode system is selected from one of the following combinations:

[0017] Combination 1 contains: 0.8-1.2 M potassium hydroxide, 0.8-1.2 M sodium formate (FA), and deionized water as solvent;

[0018] Combination 2 contains: 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol and deionized water, and the volume ratio of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol and deionized water is 1~5:20~30:5~10.

[0019] Furthermore, the electrolyte of the three-electrode system contains 1M potassium hydroxide, 1M sodium formate, and deionized water as the solvent. The surface modification treatment is performed by applying a constant voltage of -1.0 to -1.3 V to the three-electrode system for 15 to 18 hours. When Combination 1 is used as the cathode treatment solution, it not only effectively reduces the amount of oxides formed on the metal surface, but more importantly, forms a regular lattice structure on the metal surface.

[0020] Furthermore, the electrolyte contains: 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol, and deionized water; the volume ratio of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol, and deionized water is 1-5:20-30:5-10; the surface modification treatment is performed by applying a constant voltage of -0.9 to -1.3 V to the three-electrode system for 12-14 hours. When combination 2 is used as the cathode treatment solution, in addition to forming a regular superlattice on the surface, an adsorption layer of organosilane molecules containing Si-C and C-H bonds is also formed on the metal surface.

[0021] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following steps:

[0022] S1. Grind and clean the surface of the metal material to be processed;

[0023] S2. Constructing a three-electrode system, using the metal material as the working electrode and applying a cathodic voltage to perform surface modification, thereby reconstructing the metal surface lattice and forming a dense adsorption layer of corrosion-inhibiting molecules;

[0024] The three-electrode system includes: the metal material as a working electrode, a platinum sheet as an auxiliary electrode, and silver / silver chloride or saturated calomel (SCE) as a reference electrode;

[0025] The applied cathode constant voltage is between -0.8 and -1.5 V, and the power-on time is 12 to 20 hours;

[0026] S3. After the power is turned off, clean and dry the treated metal samples.

[0027] Preferably, in S1, the metal sample surface is polished sequentially using sandpaper of varying grits, then rinsed with deionized water and ethanol, cleaned with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, and finally dried with hot air. This pretreatment process ensures a clean metal surface free of oil and oxide layer interference, providing a good surface condition for subsequent electrochemical treatment and facilitating the uniform formation of a passivation film.

[0028] Preferably, in S3, the treated metal sample is washed with deionized water and ethanol for 3 minutes respectively, and then dried with hot air. This post-treatment can completely remove residual electrolyte and loose materials on the surface, ensure that the formed passivation film is pure and dense, and improve its bonding strength with the metal substrate and corrosion resistance.

[0029] The present invention also provides application of the above method in improving the oxidation resistance of metal surfaces.

[0030] Beneficial effects

[0031] The method of the present invention uses cathode voltage treatment to achieve metal surface lattice reconstruction, subverting the technical concept of traditional anodic oxidation, so that the passivation film forms a regular lattice structure, greatly reducing defects in the film, effectively blocking the penetration of corrosive media, and significantly improving the corrosion resistance of the metal.

[0032] The cathode voltage treatment of the present invention is different from traditional cathodic protection technology. It does not require continuous power supply to maintain the protection effect. Instead, it achieves permanent changes in the metal surface structure through a one-time treatment, forming a passivation film with long-lasting protective capabilities, thereby reducing long-term maintenance costs.

[0033] The two electrolyte combinations provided by the present invention target different protection mechanisms. Combination 1 (potassium hydroxide + sodium formate) mainly achieves lattice reconstruction on the metal surface and reduces the oxide content; combination 2 (1H,1H,2H,2H-perfluorodecyltrimethoxysilane + ethanol + deionized water) forms a dense organic silane molecular adsorption layer on the reconstructed surface. Both mechanisms can significantly improve the corrosion resistance of the metal.

[0034] The method of the present invention is simple to operate, can be realized using conventional electrochemical equipment, is suitable for industrial large-scale application, and has good practicality and promotion value.

[0035] Compared with traditional passivation films, the passivation film prepared by the present invention has lower surface energy and fewer defects, which increases the corrosion energy barrier and can provide a more lasting protective effect in harsh environments (such as acidic solutions and chloride ion-containing environments). BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The performance comparison of the iron sheet before and after sodium formate cathode treatment is shown in Figure 1. (a) shows the open circuit potential comparison in a sulfuric acid solution with a pH of 4.5, and (b) shows the X-ray diffraction (XRD) comparison of the film layer.

[0037] Figure 2 The transmission electron microscope (TEM) lattice image of the iron sheet surface after FA cathode treatment; wherein, (a) is the preparation method of the sample transmission electron microscope, and (b) is the transmission electron microscope lattice distribution image of the iron sheet surface after sodium formate cathode treatment;

[0038] Figure 3 Comparison of optical images of iron sheet before and after 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment; (a) is before 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment, and (b) is after 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment;

[0039] Figure 4Comparison of the performance of iron sheets before and after cathode treatment with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, where (a) is the open circuit potential comparison in 0.1M sodium chloride solution, and (b) is the Raman comparison of the film layer;

[0040] Figure 5 The AC impedance spectra of the iron sheet before and after 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment, including (a) EIS impedance spectrum comparison and (b) Bode phase angle diagram comparison;

[0041] Figure 6 This is the Tafel diagram of the iron sheet before and after 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment;

[0042] Figure 7 The open circuit potential of nickel-plated iron sheet after potassium hydroxide cathode treatment in sulfuric acid solution with pH = 4.5;

[0043] Figure 8 The open circuit potential of the iron sheet in 0.1 M sodium chloride solution after being directly immersed in 1H,1H,2H,2H-perfluorodecyltrimethoxysilane for 12 hours;

[0044] Figure 9 The open circuit potential of the iron sheet after traditional chemical passivation treatment in sulfuric acid solution with pH = 4.5;

[0045] Figure 10 The open circuit potential of the chemical conversion coated iron sheet in a sulfuric acid solution with pH = 4.5;

[0046] Figure 11 The open circuit potential of an iron sheet treated with potassium hydroxide cathode for 10 minutes in a sulfuric acid solution with a pH of 4.5;

[0047] Figure 12 The following is a comparison of the appearance of iron sheets treated with different methods in pH 4.5 sulfuric acid over a period of time. (a) is the cathode-treated iron sheet after 80 hours, and (b) is the blank control iron sheet after 10 hours.

[0048] Figure 13 is the open circuit potential in a pH 4.5 sulfuric acid solution after cathodic treatment in a mixed solution of oxalic acid and potassium hydroxide for 15 hours;

[0049] Figure 14 The open circuit potential of an iron sheet in a sulfuric acid solution with a pH of 4.5 after being treated with potassium hydroxide cathode for 15 hours and then immersed in a sodium formate solution for 12 hours;

[0050] Figure 15It is the open circuit potential in a pH 4.5 sulfuric acid solution after cathode treatment in a mixed solution of sodium sulfide and potassium hydroxide for 15 hours. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described in detail below through specific examples. It should be understood that the implementation of the present invention is not limited to the following examples, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention.

[0052] In the present invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. The methods in the following examples are all conventional methods in the art unless otherwise specified.

[0053] Unless otherwise specified, the reagents used in the following examples can be purchased from conventional biochemical reagent stores.

[0054] Example 1

[0055] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0056] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0057] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0058] 3. Apply cathode voltage to prepare ultra-high corrosion-resistant passivation film on the surface of iron sheet. The specific operation is as follows: using electrochemical workstation, in 1.0 M potassium hydroxide + 1.0 M sodium formate aqueous solution, use the above polished iron sheet as working electrode, platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.2 V for 15 hours;

[0059] 4. After the cathode is energized, collect the working electrode iron sheet product and rinse it with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide and sodium formate on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test.

[0060] 5. In water, sulfate will participate in some chemical reactions. When there is a certain amount of hydrogen ions in the environment, an acidic environment will be formed, thereby accelerating the corrosion of iron. Therefore, the iron sheet with the cathode surface passivated by directional current and the untreated iron sheet were placed in a sulfuric acid solution with pH = 4.5 for electrochemical testing, and their open circuit potential was recorded. The results are as follows: Figure 1 As shown in Figure a, the results show that at the beginning of the test, the open-circuit potential of the untreated iron sheet drops rapidly, dropping from the initial potential to approximately -0.6 V before stabilizing. However, after the cathode treatment, the potential of the iron sheet slowly rises and remains at a relatively high level for a longer period of time, with minimal fluctuations. This indicates that the cathode treatment creates a relatively stable electrochemical environment on the iron sheet's surface, reducing its corrosion tendency. Figure 1 Figure b shows the X-ray diffraction (XRD) results of the iron sheet before and after cathode treatment. The results show that the untreated iron sheet has more impurity peaks and the presence of diffraction peaks of iron oxidation products. However, after FA cathode treatment, the diffraction peak of the Fe (110) crystal plane is enhanced and the oxide diffraction peak disappears. This shows that applying cathode voltage to the metal surface to achieve directional passivation can effectively improve the corrosion resistance of the passivation film.

[0061] 6. Perform transmission electron microscopy (TEM) on the iron sheet after potassium hydroxide cathode treatment to observe the morphology of the passivation film on the sample surface. The results are as follows: Figure 2 shown. Figure 2 Figure a shows the sample preparation method for transmission electron microscopy (TEM). The upper layer of an iron sheet is embedded in an epoxy resin layer and then secured to a sample chuck for ultrathin sectioning, achieving nanometer-level precision. After sectioning, the sample is transferred to a TEM grid for TEM observation. Figure 2 As can be seen in Figure b, after cathode passivation treatment, more dense lattices with consistent directions and regular arrangements are formed on the surface of the iron sheet, while the lattices inside the iron sheet are inconsistent in direction and the arrangement is relatively chaotic.

[0062] The iron sheet is passivated by passing electricity through the cathode. An electrochemical reduction reaction occurs at the cathode, and the high-valence trivalent iron ions (Fe 3+ ) will gain electrons and be reduced to low-valent ions. Changes in the valence of ions will lead to an increase in their ionic radius, a change in their coordination number, and possible changes in the coordination environment around them. In order to adapt to the new ionic state and space occupancy requirements, crystallographic reconstruction will be induced on the surface of the iron sheet to form a dense superlattice reconstruction layer. This dense structure can effectively block the contact between the external corrosive medium sulfate and the iron matrix, thereby inhibiting the oxidation and corrosion reaction of the iron sheet, greatly improving the overall antioxidant performance of the iron sheet surface, and the corrosion resistance is improved by several orders of magnitude compared to untreated bare iron.

[0063] Example 2

[0064] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0065] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0066] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0067] 3. Prepare cathode treatment solution: Add 0.5 mL of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDTMS) to an ethanol-water solution (20 mL of anhydrous ethanol and 5 mL of deionized water) and stir for 20 minutes.

[0068] 4. The cathode voltage modification method was used to prepare an ultra-high corrosion-resistant passivation film on the surface of the iron sheet. The specific operation was to use an electrochemical workstation, use the polished iron sheet as the working electrode, and a platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, which was placed in the prepared cathode treatment solution and energized in the potential window of -1.2 V for 12.5 hours;

[0069] 5. After the cathode is energized, the working electrode iron sheet product is collected and rinsed with anhydrous ethanol for 3 minutes to remove the free 1H,1H,2H,2H-perfluorodecyltrimethoxysilane on the surface of the iron sheet. After drying with hot air, the corrosion resistance test is performed.

[0070] 6. Electrochemical test was conducted on the iron sheet treated with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode. Test conditions: the iron sheet after cathode power treatment was placed in 0.1M sodium chloride solution for electrochemical test and its open circuit potential was recorded. The results are as follows: Figure 4 shown.

[0071] The optical images of the surface of bare Fe treated with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode are shown in Figure 2. Figure 3 As shown in Figure 1, the surface of the iron sheet after cathode voltage treatment with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane is significantly smoother and has fewer impurities. The iron sheet before and after cathode voltage treatment was subjected to electrochemical testing. The test conditions were as follows: the iron sheet after cathode power treatment and the untreated iron sheet were placed in 0.1M sodium chloride solution for electrochemical testing, and their open circuit potential was recorded. The results are shown in Figure 1. Figure 4 As shown in a. Chloride ion (Cl -Chloride ions are highly penetrating and corrosive, adsorbing onto the iron surface and replacing oxygen atoms in the passivation film, thereby destroying the passivation film. Once the passivation film is destroyed, the iron is exposed to the corrosive medium, accelerating the corrosion process. Natural and industrial environments such as seawater, salt lakes, groundwater, and media used in some chemical production processes contain large amounts of chloride ions. Therefore, testing the corrosion resistance of iron in a chloride ion environment is of great significance for evaluating its durability in practical applications.

[0072] Figure 4 The results in middle a show that the potential value of the iron sheet increased significantly after cathode treatment with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, and its corrosion resistance was enhanced. Figure 4 b is the Raman test result of the iron film before and after the 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode treatment. -1 The characteristic peak may come from the Fe-O bond. After the cathode treatment with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, the vibration of the Fe-O bond disappears. -1 Si-C bond appears, 2844 cm -1 and 2882 cm -1 Two obvious characteristic peaks appeared, which were mainly related to the symmetric and antisymmetric stretching vibrations of the saturated CH bond. The results showed that the cathode treatment caused the silane-related substances to act on the iron surface. Fe reacted with the silanol group (-SiOH) in the hydrolysis product of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane to form a ligand, which was adsorbed on the iron surface in the form of a chemical bond (Si-O-Fe). This made up for the defect sites on the surface of the directional passivation film, greatly increased the density of the passivation film surface, and effectively blocked oxygen (O2) and chloride ions (Cl - ) and other oxidizing / corrosive species diffuse inward and interact with the internal iron, thereby inhibiting iron corrosion. The introduction of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane can further improve the corrosion resistance of the iron sheet when the cathode is energized.

[0073] 7. The iron sheet treated with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode was subjected to electrochemical testing. The test conditions were as follows: the iron sheet after cathode power treatment was placed in a PH4.5 sulfuric acid solution for electrochemical testing, and its AC impedance value and Tafel polarization curve test were recorded. The results are as follows: Figure 5 、 6 shown.

[0074] Figure 5These are the EIS impedance spectroscopy (EIS) graphs and Bode phase angle diagrams of bare iron and iron sheets treated with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode in a pH 4.5 sulfuric acid solution. Figure 5 The results in Figure a show that the overall impedance of untreated bare iron is low, indicating that the charge transfer resistance at the bare iron electrode interface is low in a pH 4.5 sulfuric acid solution, making corrosion reactions more likely. However, after cathodic treatment, the diameter of the semicircle increases significantly, indicating a significant increase in impedance, which continues to rise with decreasing frequency. This indicates that after cathode power is applied, the silanol groups in 1H,1H,2H,2H-perfluorodecyltrimethoxysilane form a high-resistance adsorption layer with the regular superlattice layer, hindering the corrosion current and increasing the interfacial impedance by 1-2 orders of magnitude, significantly inhibiting corrosion. Furthermore, the cathodic-treated iron sheet exhibits a small semicircle in the high-frequency region and a sloping upward trend in the low-frequency region, indicating the presence of an inner regular superlattice passivation layer and an outer adsorption film at the interface. The corrosion process is controlled by a combination of "film resistance and diffusion." Through synergistic effects, cathodic power application transforms the bare iron's "highly active corrosion interface" into a "highly resistive protective interface," providing a better electrochemical modification strategy for corrosion protection of iron in acidic environments. Figure 5 b is the Bode phase angle diagram of the two. It can be seen that the high frequency area of ​​bare iron (10 4 -10 5 Hz) has low impedance (small |Z|). As frequency decreases, the impedance first increases and then decreases (a single peak appears), indicating that the interface is dominated by a single time constant (double-layer capacitance + charge transfer resistance), and the corrosion reaction is not significantly hindered by the protective layer. However, the impedance of the cathodically treated iron is significantly higher in the high-frequency region than that of bare iron, and the impedance continues to rise as frequency decreases (without a clear drop-off), indicating that after cathodically treating, a high-resistance protective layer (such as a regular superlattice passivation film) forms at the interface, while the low-frequency region is dominated by diffusion processes. Furthermore, compared to the single phase angle peak of bare iron, the cathodically treated iron exhibits two phase angle peaks. The high-frequency impedance (|Z|) of the cathodically treated iron is much higher than that of bare iron, indicating that the protective film significantly increases the transmission resistance of high-frequency current, significantly inhibiting corrosion, which corresponds to the EIS AC impedance value.

[0075] Figure 6 The Tafel curves of bare iron and cathodically treated iron in a pH 4.5 sulfuric acid solution are shown. The results show that the self-corrosion potential of bare iron is about -0.29 V, while the self-corrosion potential of cathodically treated iron is about -0.18 V, with a potential "positive shift" of about 0.11 V, indicating that the oxidation tendency of iron is significantly reduced (corrosion tendency is weakened) after cathodically treated iron. In a pH 4.5 sulfuric acid solution, the i0 of bare iron is usually greater than 10 -5 A / cm 2 , and after cathode treatment it can be reduced to 10 -7 ~10 -6A / cm 2 The self-corrosion current density is significantly reduced, and the cathode-treated iron sheet has a significant protective effect in pH 4.5 sulfuric acid solution, which is suitable for weak acid corrosion environment.

[0076] Example 3

[0077] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0078] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0079] 2. Grind the surface of the sliced ​​iron plate with 600#, 1200#, and 2000# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0080] 3. Prepare a nickel metal layer on the surface of the iron plate. The specific operation is to use a stabilized power supply to prepare a nickel metal layer on the surface of the iron plate. The nickel sulfate hexahydrate (NiSO4·6H2O) 0.38M, boric acid (H3BO3) 0.4M, L-ascorbic acid (C6H8O6) 0.03M, sodium dodecyl sulfate (CH3(CH2) 11 OSO3Na) 0.0035M solution, using the above polished iron plate as the negative electrode, a platinum sheet (1×1cm -2 ) is the positive electrode and is energized at a constant voltage of -2.5V for 30 minutes;

[0081] 4. After the power is turned on, collect the nickel-plated iron plate and rinse it with anhydrous ethanol for 3 minutes to remove the free electrolyte on the surface, then blow it dry with hot air and set aside;

[0082] 5. Apply cathode voltage to prepare ultra-high corrosion-resistant passivation film on the surface of nickel-plated iron plate. The specific operation is to use electrochemical workstation, in 1.0 M potassium hydroxide aqueous solution (pH about 14), use the nickel-plated iron plate as working electrode, platinum sheet (1×1 cm -2 ) as the auxiliary electrode and calomel electrode as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.3 V for 15 hours;

[0083] 6. After the cathode is energized, collect the nickel-plated iron plate product of the working electrode and rinse it with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide electrolyte on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test.

[0084] 7. The nickel-plated iron plate after surface directional passivation was subjected to electrochemical testing. The test conditions were as follows: the nickel-plated iron plate after cathode power treatment was placed in a sulfuric acid solution with pH = 4.5 for electrochemical testing, and its open circuit potential was recorded. The results were as follows: Figure 7shown.

[0085] The results show that when the nickel-plated iron plate was cathode-energized and placed in a pH 4.5 sulfuric acid solution, the initial potential gradually increased from around -0.45 V at the beginning of the test and remained at a relatively high level for a long time. After 24 hours, the potential was approximately -0.2 V, indicating a low corrosion tendency. This is primarily due to the nickel coating acting as a continuous metal barrier covering the iron substrate. It not only covers surface defects such as microcracks and pores, but also directly blocks contact between the corrosive medium, sulfate, and the iron substrate, significantly slowing the corrosion process. Furthermore, applying a cathodic voltage in the potassium hydroxide solution forms a stable, dense, directional passivation layer on the nickel layer, further hindering sulfate adsorption and effectively improving the corrosion resistance of the passivation film. The synergistic effect of the nickel coating and the superlattice passivation layer effectively reduces the corrosion tendency of the iron sheet and enhances its overall protective effect.

[0086] Comparative Example 1

[0087] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0088] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0089] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0090] 3. Prepare the corrosion inhibition solution: add 1 mL of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane to the ethanol aqueous solution (including 20 mL of anhydrous ethanol and 5 mL of deionized water) and stir for 20 minutes;

[0091] 4. Soak the polished bare iron in the prepared corrosion inhibition solution for 12 hours to form a corrosion-resistant protective layer on the surface of the iron sheet;

[0092] 5. After soaking, collect the iron sheet products and rinse them with anhydrous ethanol for 3 minutes to remove the free 1H,1H,2H,2H-perfluorodecyltrimethoxysilane on the surface of the iron sheet. After drying with hot air, perform corrosion resistance test.

[0093] 6. After being soaked in 1H,1H,2H,2H-perfluorodecyltrimethoxysilane slow-release solution for 12 hours, the iron sheet was placed in 0.1M sodium chloride solution for electrochemical testing and its open circuit potential was recorded. The results are as follows: Figure 8As shown, after immersion in the slow-release solution of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, the open-circuit potential drops sharply in the first half hour before briefly rising. This is likely due to the rapid and complex electrochemical reactions between the iron sheet and the sodium chloride solution upon its initial placement, which leads to corrosion. Furthermore, the hydrophobic protective film formed by 1H,1H,2H,2H-perfluorodecyltrimethoxysilane on the iron sheet's surface begins to interact with ions in the solution, reducing the potential for electrochemical corrosion. Consequently, the open-circuit potential fluctuates significantly. As corrosion time increases, the open-circuit potential gradually decreases, and the fluctuations diminish. Subsequently, the film formed by 1H,1H,2H,2H-perfluorodecyltrimethoxysilane may begin to be gradually eroded by the chloride ions and other corrosive media in the solution. This increases the contact area between the iron and the solution, leading to a dominant anodic dissolution reaction on the iron surface. This damages the film and causes pitting corrosion on the iron sheet.

[0094] and Figure 4 Compared with the iron sheet treated with 1H,1H,2H,2H-perfluorodecyltrimethoxysilane cathode, the iron sheet only immersed in 1H,1H,2H,2H-perfluorodecyltrimethoxysilane has poor corrosion resistance and cannot effectively block the invasion of chloride ions. Figure 2 This study demonstrates that a dense passivation layer can be reconstructed on the iron surface by applying a cathode current. Furthermore, the introduction of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (1H,1H,2H,2H-perfluorodecyltrimethoxysilane) alkylthiol ligands allows the 1H,1H,2H,2H-perfluorodecyltrimethoxysilane to coordinate with steps or defect sites that are not well protected by the passivation layer. These defect sites are vulnerable to corrosion, and the introduction of alkylthiol ligands further fills these gaps, significantly improving the overall antioxidant properties of the iron surface.

[0095] Comparative Example 2

[0096] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0097] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0098] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0099] 3. Chemically passivate the polished iron sheet by immersing it in a 15% volume fraction sodium nitrate solution at 50°C for 20 minutes. When the surface of the iron sheet gradually loses its metallic luster and turns dark gray or blue-black, indicating the formation of an oxide film, remove the sample.

[0100] 4. After the chemical passivation is completed, quickly remove the iron sheet and rinse it with anhydrous ethanol for 3 minutes to remove the acid remaining on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test;

[0101] 5. Perform electrochemical test on the chemically passivated iron sheet. Test conditions: Place the chemically passivated iron sheet in a sulfuric acid solution with pH = 4.5 for electrochemical test and record its open circuit potential. The results are as follows: Figure 9 shown.

[0102] The results show that the initial open circuit potential of the sample after chemical passivation in pH = 4.5 sulfuric acid solution is relatively high, at -0.3V. This is because the passivation film formed by chemical passivation has a certain protective effect, making the initial electrode potential of the iron sheet in sulfuric acid solution at a relatively high level. However, as time goes by, the SO4 2- As ions continuously interact with the passivation film or the iron substrate, the open-circuit potential gradually decreases, with a rapid rate of decline. The results indicate that chemically passivated iron cannot maintain a well-developed passivation state in sulfuric acid at pH 4.5. Traditional chemical passivation of iron sheets using nitric acid solution primarily aims to form a dense oxide film (such as ferrosoferric oxide (Fe3O4) or ferric oxide (Fe2O3)) on the surface. Compared to the dense superlattice passivation film formed by cathode current flow, this oxide film offers poor corrosion resistance and is unable to provide long-term protection for the iron sheet.

[0103] Comparative Example 3

[0104] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0105] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0106] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0107] 3. Use traditional methods to form a chemical conversion coating on the surface of the iron sheet. The specific operation is to prepare a conversion solution containing 15g / L zinc oxide (ZnO), 20mL / L phosphoric acid (H3PO4), and 3g / L sodium nitrate (NaNO3). Place the polished iron sheet in the phosphating solution and soak it at 50°C for 15 minutes to form a chemical conversion coating.

[0108] 4. After soaking, collect the soaked iron products and rinse them with anhydrous ethanol for 3 minutes to remove the free acid on the surface of the iron sheets. After drying with hot air, perform corrosion resistance test.

[0109] 5. The iron sheet with chemical conversion coating is subjected to electrochemical test. Test conditions: the iron sheet treated with traditional conversion coating is placed in a sulfuric acid solution with pH=4.5 for electrochemical test and its open circuit potential is recorded. The results are as follows: Figure 10 shown.

[0110] The results show that the iron sheet treated with chemical conversion coating has a higher initial open-circuit potential of approximately -0.25V compared to those treated with cathodic treatment and chemical passivation, indicating a lower likelihood of electrochemical corrosion. This is likely because the traditional phosphate chemical conversion coating method forms a dense coating composed of zinc phosphate tetrahydrate (Zn3(PO4)2·4H2O) and phosphophyllite (Zn2Fe(PO4)2·4H2O) on the iron substrate. This coating provides an insulating barrier between the iron sheet and sulfate ions, imparting improved initial corrosion resistance. However, the resulting phosphate coating is porous and rough, with numerous tiny pores. Sulfate ions, the corrosive medium, can still penetrate the iron substrate through these pores. Consequently, the open-circuit potential decreases over time, stabilizing to -0.5V after 3 hours, at which point localized corrosion initiates on the iron sheet's surface.

[0111] Therefore, compared with the superlattice corrosion-resistant passivation films formed in Examples 1 and 2, the chemical conversion coating still cannot effectively resist the invasion of corrosive media and does not have long-term protective capabilities.

[0112] Comparative Example 4

[0113] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0114] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0115] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0116] 3. The polished iron sheet was subjected to cathode voltage treatment. In order to form a contrast with Example 1, the cathode treatment time was reduced in this example. The specific operation was as follows: using an electrochemical workstation, in a 1.0 M potassium hydroxide + 1.0 M sodium formate aqueous solution, the polished iron sheet was used as the working electrode, and a platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.2 V for 10 minutes;

[0117] 4. After the cathode is energized, collect the working electrode iron sheet product and rinse it with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide and sodium formate on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test.

[0118] 5. Perform electrochemical test on the iron sheet after 10 minutes of cathode treatment. Test conditions: Place the iron sheet after 10 minutes of cathode treatment in pH=4.5 sulfuric acid solution for electrochemical test and record its open circuit potential. The results are as follows: Figure 11 shown.

[0119] After 10 minutes of cathode treatment, the potential of the iron sheet rises slightly in the first 20 minutes, then gradually decreases and eventually stabilizes at -0.5V, indicating a clear corrosion tendency. The only difference between Comparative Example 3 and Example 1 is the reduction in power-on time, but the open circuit potential data of Comparative Example 3 is significantly worse than that of Example 1. This is mainly because the cathode power-on time is too short, and crystallographic reconstruction has not yet occurred on the surface of the iron sheet. Compared with Example 1, a dense superlattice passivation film has not formed, which cannot prevent the contact of the external corrosive medium sulfate ions with the substrate. Therefore, the corrosion resistance of the sample is poor. The comparative results show that appropriately extending the cathode power-on time can achieve better technical effects.

[0120] Comparative Example 5

[0121] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0122] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0123] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0124] 3. In order to contrast with the effect of cathode treatment on iron sheets, this comparative example did not perform any treatment on the iron sheets. The iron sheets that were polished and not treated and the iron sheets that were treated with potassium hydroxide cathode for 15 hours were placed in pH = 4.5 sulfuric acid solution for corrosion resistance observation. The results are as follows: Figure 12 shown.

[0125] Figure 12 The iron sheet is placed in sulfuric acid with pH = 4.5 after being treated with potassium hydroxide cathode electricity. After 80 hours, the surface of the iron sheet still has metallic luster, no pitting corrosion occurs, and the corrosion resistance is good. Figure 12 b is a blank control iron sheet without any treatment placed in a sulfuric acid solution with a pH of 4.5 The appearance of the iron sheet after 10 hours shows that corrosion has already occurred, with a large amount of corrosion products attached to the surface. The results show that the corrosion resistance of the iron sheet has been significantly improved after the cathodic passivation treatment.

[0126] Comparative Example 6

[0127] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0128] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0129] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0130] 3. The polished iron sheet was subjected to cathode voltage treatment. In order to contrast with the effect of potassium hydroxide and sodium formate cathode treatment of the iron sheet in Example 1, this example used a mixed solution of oxalic acid and potassium hydroxide as the cathode treatment solution. The specific operation was as follows: using an electrochemical workstation, in a mixed aqueous solution of 1.0 M potassium hydroxide + 0.1 M oxalic acid, using the polished iron sheet as the working electrode, a platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.2 V for 15 hours;

[0131] 4. After the cathode is energized, collect the working electrode iron sheet product and rinse it with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide and oxalic acid on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test.

[0132] 5. Electrochemical test was performed on the iron sheet after the cathode treatment with oxalic acid and potassium hydroxide. Test conditions: After the cathode treatment for 15 hours, the iron sheet was placed in a sulfuric acid solution with pH = 4.5 for electrochemical test and its open circuit potential was recorded. The results are as follows: Figure 13 shown.

[0133] The result shows that, after oxalic acid and potassium hydroxide mixed solution cathode are energized, iron sheet has a higher open circuit potential, is about -0.2 V, and now iron sheet has stronger sulfate corrosion resistance. This may be because oxalic acid is a kind of weak acid, and after mixing with potassium hydroxide and existing with oxalate ions, it can form oxalate film with the metal ions on the surface of iron sheet, so as to block the invasion of sulfate. But as time prolongs, the open circuit potential of system decreases sharply, and after 1 hour, the open circuit potential is reduced to about -0.6 V, and after 1.5 hours, the potential tends to be stable at about -0.7 V, and now the sample surface causes local corrosion. This is mainly because although oxalic acid-potassium hydroxide mixed solution is alkaline, oxalate film crystallinity is strong, and it is easy to be protonated and dissolved to form pores or microcracks in acidic sulfuric acid solution, and it is impossible to effectively block the penetration of sulfate in solution, causing later potential to be difficult to maintain high value. And in the sodium formate system in Example 1, the formic acid solubility generated after formate protonation is relatively low, and is more stable in weak acid, and more lasting protective ability is provided to iron sheet.

[0134] Comparative Example 7

[0135] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0136] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0137] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0138] 3. The polished iron sheet was subjected to cathode voltage treatment. In order to contrast with the effect of potassium hydroxide and sodium formate cathode treatment of the iron sheet in Example 1, this example used potassium hydroxide alone as the cathode treatment solution and soaked in sodium formate aqueous solution for a period of time after the power was turned off. The specific operation was as follows: Using an electrochemical workstation, in a 1.0 M potassium hydroxide aqueous solution, the polished iron sheet was used as the working electrode, and a platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.2 V for 15 hours;

[0139] 4. After the cathode is energized, the iron sheet is immersed in a 1M sodium formate aqueous solution for 12 hours. After the immersion, the working electrode iron sheet product is collected and rinsed with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide and oxalic acid on the surface of the iron sheet. After drying with hot air, the corrosion resistance test is performed;

[0140] 5. Electrochemical test of the iron sheet treated with cathode and soaked in sodium formate. Test conditions: Place the treated iron sheet in a sulfuric acid solution with pH = 4.5 for electrochemical test and record its open circuit potential. The results are as follows: Figure 14 shown.

[0141] Figure 14 The results show that, just after being put into pH=4.5 sulfuric acid solution, the open circuit potential will show a short upward trend in the first 15 minutes, rising to about -0.32 V. This is mainly because when sodium formate is soaked in potassium hydroxide cathode treatment, sodium formate generates a protective film on the surface of the iron sheet through "diffusion, adsorption, reaction". However, in an acidic environment, the protective film will gradually dissolve and destroy, the film is loose and contains more defects, and the corrosive medium sulfate ions easily reach the metal surface through the defects, causing the electrode surface state to change sharply, the corrosion activity to rise rapidly, the corrosion to accelerate, and the open circuit potential to continue to shift negatively. In Example 1, in the cathode powered environment, the carbonate-containing, formate protective film formed by the synergistic effect of potassium hydroxide and sodium formate is denser and more tightly combined with the matrix, and is more difficult to be infiltrated and dissolved by the corrosive medium, and its stability is far better than this comparative example.

[0142] Comparative Example 8

[0143] A method for preparing a corrosion-resistant passivation film on a metal surface, the method comprising the following specific steps:

[0144] 1. Sampling was performed on the iron plate and then slicing was performed. The size of all samples used in the experiment was 10mm×10mm×3mm.

[0145] 2. Grind the surface of the sliced ​​iron sheet with 1200# and 1500# silicon carbide (SiC) sandpaper respectively, rinse the surface with deionized water and ethanol, and clean it with ethanol in an ultrasonic cleaner for 3 minutes to remove surface impurities, blow dry with hot air and set aside;

[0146] 3. The polished iron sheet was subjected to cathode voltage treatment. In order to contrast with the effect of potassium hydroxide and sodium formate cathode treatment of the iron sheet in Example 1, this example used a mixed solution of sodium sulfide and potassium hydroxide as the cathode treatment solution. The specific operation was as follows: using an electrochemical workstation, in a mixed aqueous solution of 1.0 M potassium hydroxide + 0.11 M sodium sulfide, using the polished iron sheet as the working electrode, a platinum sheet (1×1 cm -2 ) as the auxiliary electrode and silver / silver chloride as the reference electrode to form a three-electrode system, and the three-electrode system was energized in a potential window of -1.2 V for 15 hours;

[0147] 4. After the cathode is energized, collect the working electrode iron sheet product and rinse it with anhydrous ethanol for 3 minutes to remove the free potassium hydroxide and sodium sulfide on the surface of the iron sheet. After drying with hot air, perform the corrosion resistance test.

[0148] 5. Electrochemical test was performed on the iron sheet after the cathode treatment with sodium sulfide and potassium hydroxide. Test conditions: the iron sheet after the cathode treatment for 15 hours was placed in a sulfuric acid solution with pH = 4.5 for electrochemical test and its open circuit potential was recorded. The results are as follows: Figure 15 shown.

[0149] Compared to other treatment methods, the potential of the sodium sulfide-potassium hydroxide system after cathode power application is extremely negative, reaching -0.61 V. This is primarily because the iron sulfide formed during the reaction has a much lower electrode potential than the pure iron substrate. The presence of this film lowers the overall open-circuit potential, resulting in a very strong initial negative potential. Furthermore, the presence of the sulfide film during cathode power application may inhibit the formation of a passive film, causing the metal to remain in an "activated state" or "low-potential reduced state" for a long period of time, preventing the potential from increasing through natural passivation. This results in a persistently strong initial negative potential. With extended immersion in sulfuric acid, the sulfide film gradually dissolves, intensifying corrosion activity on the iron substrate surface and promoting corrosion.

[0150] In summary, the present invention connects a metal to the cathode of a potentiostat, uses a specially formulated electrolyte, and applies a low voltage for a specified period of time to restructure the metal surface, forming a regular superlattice structure with low surface energy. This regular lattice structure significantly reduces the presence of defects, while the low-surface-energy crystal planes increase the corrosion barrier, effectively improving the corrosion resistance of the metal passivation film.

[0151] Traditional chemically modified passivation films can adsorb corrosion inhibitor ions and molecules on their surfaces. While this can effectively block corrosion from external corrosive media, the passivation film itself is often defective, resulting in a high degree of defects in the adsorption layer, making it difficult to effectively block external ion corrosion. The present invention, based on the regular lattice structure of the reconstructed metal surface, coordinates the corrosion inhibitor molecule adsorption layer, allowing the corrosion inhibitor molecules to adsorb regularly on the lattice surface, making the adsorption layer structure more compact and effectively resisting the infiltration of external corrosive ions, thereby significantly improving the long-term protective performance of the metal.

Claims

1. A method for preparing a corrosion-resistant passivation film on a metal surface, characterized in that: The steps include: After the metal surface is polished and cleaned, a three-electrode system is constructed and a cathode voltage is applied to the metal to perform surface modification, thereby achieving lattice reconstruction on the metal surface and forming a dense adsorption layer of corrosion-inhibiting molecules. The metal is iron or nickel; The three-electrode system includes: a metal as a working electrode, a platinum sheet as an auxiliary electrode, and silver / silver chloride or saturated calomel as a reference electrode; The electrolyte of the three-electrode system includes 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol and deionized water; the volume ratio of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, ethanol and deionized water is 1~5:20~30:5~10; the surface modification treatment condition is to apply a constant voltage of -0.9~-1.3 V to the three-electrode system for 12~14 hours.

2. The method for preparing a corrosion-resistant passivation film on a metal surface according to claim 1, wherein: The metal surface polishing and cleaning comprises: polishing the metal surface with sandpaper of different mesh sizes in sequence, then rinsing the surface with deionized water and ethanol, cleaning with ethanol in an ultrasonic cleaner to remove surface impurities, and finally drying with hot air.

3. The method for preparing a corrosion-resistant passivation film on a metal surface according to claim 2, wherein: The cleaning time with ethanol in the ultrasonic cleaner is 2 to 4 minutes.

4. The method for preparing a corrosion-resistant passivation film on a metal surface according to claim 1, wherein: The surface-modified metal was washed with deionized water and ethanol, respectively, and then dried with hot air.

5. Use of the method according to any one of claims 1 to 4 in improving the oxidation resistance of metal surfaces.

6. Use of the method according to any one of claims 1 to 4 in improving the corrosion resistance of metal surfaces.

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