Corrosion inhibition film based on composite film layer and preparation method thereof

Abstract

The invention discloses a corrosion inhibition film based on a composite film layer and a preparation method of the corrosion inhibition film. The preparation method comprises the following steps that S1, a carbon steel sample is prepared and pretreated; s2, a passivating agent is dissolved in water, the pH is adjusted to range from 5 to 6.5, and a passivating agent concentrated solution with the concentration ranging from 0.2 M to 0.325 M is obtained; s3, simulated formation water is prepared, mixed gas of carbon dioxide and oxygen is introduced into the simulated formation water, then the passivator concentrated solution is added according to the volume ratio of 1: 25, the mixture is stirred to be uniform, and a passivator solution is obtained; s4, the pretreated carbon steel sample is placed in the passivating agent solution to be passivated for 4-8 h under the condition of 30-50 DEG C, and a passive film layer is generated on the carbon steel sample; and S5, preparing a 100ppm corrosion inhibitor solution, adding the corrosion inhibitor solution into the solution in the step S4, and adsorbing for 12-36 hours at the temperature of 30-50 DEG C, so that the carbon steel sample on which the passive film layer is generated is coated with a corrosion inhibitor layer, and the corrosion inhibition film of the composite film layer is obtained. The corrosion resistance of metal can be improved, and technical support is provided for oil and gas field exploitation.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field corrosion prevention, and in particular to a corrosion inhibition film based on a composite film layer and a preparation method thereof. Background Art

[0002] As my country's economy continues to develop, energy demand is increasing day by day, and the importance of stable crude oil supply is becoming more and more prominent. At present, my country's dependence on foreign crude oil exceeds 70%, which poses a huge challenge to energy security, and it is urgent to increase domestic crude oil production.

[0003] Among the measures to increase crude oil production, gas injection and water injection can increase production, but they will form CO 2 -O 2 Coexistence environment, in CO 2 -O 2 In an acidic environment, the carbon steel adsorption corrosion inhibition film has poor stability and is easily damaged, causing serious corrosion problems. 2 -O 2 Corrosion problems not only increase oilfield costs and affect production efficiency, but may also cause safety accidents and threaten personnel and the environment. Therefore, in-depth research on the damage mechanism of corrosion inhibition films and the development of efficient corrosion inhibition films are extremely critical to solving oilfield corrosion problems, ensuring the safety of energy facilities and promoting the sustainable development of the oil extraction industry. It will also help overcome existing technical bottlenecks, fill technical gaps, and meet the urgent needs of oilfield safety production and efficient operation. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a corrosion-inhibiting film based on a composite film layer and a preparation method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] On the one hand, a method for preparing a corrosion-inhibiting film based on a composite film layer is provided, comprising the following steps:

[0007] S1: preparing a carbon steel sample and pretreating the carbon steel sample;

[0008] S2: dissolving the passivating agent in water, and adjusting the pH to 5-6.5 by a pH adjusting agent to obtain a passivating agent concentrate with a concentration of 0.2-0.325M;

[0009] S3: preparing simulated formation water, introducing a mixed gas of carbon dioxide and oxygen into the simulated formation water, and then adding the passivating agent concentrate in a volume ratio of 1:25, stirring evenly, to obtain a passivating agent solution;

[0010] S4: placing the pretreated carbon steel sample in the passivating agent solution for passivation at 30-50° C. for 4-8 hours, so that a passivation film layer is formed on the carbon steel sample;

[0011] S5: Prepare a 100 ppm corrosion inhibitor solution, and add the corrosion inhibitor solution to the solution of step S4, adsorb at 30-50°C for 12-36 hours, so that the carbon steel sample with the passive film layer is covered with a corrosion inhibitor layer to obtain a composite corrosion inhibition film.

[0012] Preferably, in step S1, the pretreatment includes grinding, polishing, cleaning and drying processes performed in sequence.

[0013] Preferably, mechanical polishing and / or chemical polishing are used during the polishing process.

[0014] Preferably, during the cleaning process, acetone, ethanol and distilled water are used for ultrasonic treatment in sequence.

[0015] Preferably, in step S2, the passivating agent is any one of sodium molybdate, sodium tungstate and potassium permanganate.

[0016] Preferably, in step S2, the pH adjuster is a standard mixed solution of sodium dihydrogen phosphate and disodium hydrogen phosphate.

[0017] Preferably, in step S3, in the mixed gas, the gas pressure ratio of carbon dioxide is 90%, and the gas pressure ratio of oxygen is 10%.

[0018] Preferably, in step S5, the corrosion inhibitor in the corrosion inhibitor solution is a straight-chain compound containing hydroxyl groups and carboxyl groups.

[0019] Preferably, the corrosion inhibitor is any one or more of glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 6-hydroxyhexanoic acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, and 10-hydroxydecanoic acid.

[0020] On the other hand, a corrosion-inhibiting film based on a composite film layer is also provided, which is prepared by any of the above-mentioned methods for preparing a corrosion-inhibiting film based on a composite film layer.

[0021] The beneficial effects of the present invention are:

[0022] The corrosion inhibition film prepared by the present invention has a double-layer film, wherein the corrosion inhibitor layer can block hydrogen, so that hydrogen ions cannot continue to approach the deep passivation layer and the carbon steel surface, and the passivation layer can resist oxidation and block oxygen molecules from continuing to approach the deep carbon steel surface, so that the present invention can improve the corrosion resistance of the metal and provide technical support for oil and gas field exploitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0024] Figure 1 The corrosion inhibition film "anti-H" based on the composite film layer of the present invention + Block O 2 ” Schematic diagram of corrosion resistance principle;

[0025] Figure 2 The electrochemical fitting circuit diagram used to fit the electrochemical data;

[0026] Figure 3 It is a schematic diagram comparing the electrochemical effects of various embodiments and comparative examples. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0028] In one aspect, the present invention provides a method for preparing a corrosion inhibition film based on a composite film layer, comprising the following steps:

[0029] S1: preparing a carbon steel sample and pretreating the carbon steel sample.

[0030] In a specific embodiment, the pretreatment includes grinding, polishing, cleaning and drying in sequence. Optionally, when polishing, mechanical polishing (such as diamond, etc.) and / or chemical polishing (such as silica type polishing liquid, etc.) are used for treatment; when cleaning, acetone, ethanol and distilled water are used for ultrasonic treatment in sequence.

[0031] S2: dissolving the passivator in water, and adjusting the pH to 5-6.5 by a pH adjuster to obtain a passivator concentrate with a concentration of 0.2-0.325M.

[0032] In a specific embodiment, the passivator is any one of sodium molybdate, sodium tungstate, and potassium permanganate. In this embodiment, sodium molybdate can promote the formation of an oxide film on the metal surface during the metal passivation process. For metals such as iron and copper, the molybdenum element in sodium molybdate has multiple valence states, and can undergo complex redox reactions on the metal surface, thereby helping to form a more solid and durable oxide film. This oxide film can effectively isolate air and moisture, slow down the oxidation rate of the metal, and thus improve the corrosion resistance of the metal. However, it should be noted that the sodium molybdate and other passivators are only preferred passivators for this embodiment, and the passivator is to oxidize the carbon steel sample to form iron oxide on the surface, thereby achieving an antioxidant function. Other passivators that can achieve this purpose in the prior art may also be applicable to the present invention.

[0033] In a specific embodiment, the pH regulator is a standard mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate. It should be noted that the pH regulator of this embodiment has a strong buffering capacity, can effectively maintain the pH stability of the system, and resist pH fluctuations caused by various factors during crude oil extraction and processing; the regulating effect is mild, avoiding impact on equipment and oil quality; the chemical properties are stable, and can adapt to complex working conditions such as high temperature and high pressure; the safety is high, and will not cause great harm to the environment and operators; the cost is low, and the production cost can be reduced while ensuring the production effect. However, it is only the preferred pH regulator of the present invention. The role of the pH regulator is to adjust the pH value of the solution. Other pH regulators in the prior art that can achieve this purpose are also applicable to the present invention.

[0034] S3: Prepare simulated formation water, and introduce a mixed gas of carbon dioxide and oxygen into the simulated formation water, then add the passivator concentrate in a volume ratio of 1:25 (i.e., add 1 mL of passivator concentrate to 25 mL of water), stir evenly, and obtain a passivator solution.

[0035] In a specific embodiment, the gas pressure ratio of carbon dioxide in the mixed gas is 90%, and the gas pressure ratio of oxygen is 10%. Optionally, the short time for introducing the mixed gas is 24 hours, so as to remove the interference of other gases in the solution, ensure that the mixed gas is saturated in the solution, and ensure that the oxygen concentration and the pH value of the solution meet the requirements during subsequent oxidation.

[0036] It should be noted that, in addition to simulating the simulated formation water based on the actual formation water, the actual formation water can also be directly taken.

[0037] S4: placing the pretreated carbon steel sample in the passivating agent solution for passivation at 30-50° C. for 4-8 hours to form a passivation film layer on the carbon steel sample.

[0038] S5: Prepare a 100 ppm corrosion inhibitor solution, and add the corrosion inhibitor solution to the solution of step S4, adsorb at 30-50°C for 12-36 hours, so that the carbon steel sample with the passive film layer is covered with a corrosion inhibitor layer to obtain a composite corrosion inhibition film.

[0039] In a specific embodiment, the corrosion inhibitor in the corrosion inhibitor solution is a straight-chain compound containing a hydroxyl group and a carboxyl group. Optionally, the corrosion inhibitor is any one or more of glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 6-hydroxyhexanoic acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, and 10-hydroxydecanoic acid.

[0040] In the above embodiments, the corrosion inhibitor can show excellent performance in the corrosion inhibition process, and this phenomenon has a solid molecular dynamics theory basis. From the perspective of chemical bonding, in the linear compound molecules containing hydroxyl and carboxyl groups, functional groups such as hydroxyl and carboxyl groups can react chemically with the active sites on the surface of the oxide film to form chemical bonds. The formation of this chemical bond makes the double-layer film structure firm. The oxide film layer in the double-layer film structure can effectively prevent oxygen from undergoing reduction reactions at the cathode. The corrosion inhibitor layer can block the reduction reactions of hydrogen ions at the cathode. Thereby slowing down the occurrence of electrochemical corrosion.

[0041] At the same time, the linear compound molecules containing hydroxyl and carboxyl groups have alkyl hydrophobic chains, which are structural features that enable them to form a physical barrier, and the longer the alkyl hydrophobic chain, the stronger the physical shielding effect. The alkyl hydrophobic chains are oriented and tightly stacked on the surface of the oxide film, hindering the diffusion of the corrosive medium.

[0042] It should be noted that the corrosion inhibitors listed in the above embodiments are only preferred corrosion inhibitors of the present invention, and other straight-chain compounds containing hydroxyl and carboxyl groups with longer carbon chains in the prior art can also be applied to the present invention.

[0043] On the other hand, Figure 1 As shown, the present invention also provides a corrosion-inhibiting film based on a composite film layer, which is prepared by using any one of the above-mentioned methods for preparing a corrosion-inhibiting film based on a composite film layer.

[0044] In the present invention, the anti-corrosion principle of the corrosion-inhibiting film based on the composite film layer is as follows: the iron oxide layer of the passivation layer and the corrosion inhibitor layer have a close synergistic mechanism to jointly inhibit corrosion. The iron oxide layer acts as a physical barrier to oxygen by virtue of its own structural characteristics. Its dense crystal structure can effectively block the diffusion of oxygen molecules to the surface of carbon steel and reduce the probability of oxidation reaction between oxygen and carbon steel. When oxygen molecules pass through the iron oxide layer, due to the obstruction of its lattice, the diffusion path becomes tortuous and the diffusion rate is greatly reduced, making it difficult to reach the surface of carbon steel to participate in the corrosion reaction.

[0045] The corrosion inhibitor layer mainly inhibits the penetration of hydrogen ions by chemical adsorption. Taking 10-hydroxydecanoic acid as an example, the carboxylic acid, hydroxyl and other functional groups in its molecules can chemically adsorb with the oxide film on the surface of carbon steel. This chemical adsorption allows the corrosion inhibitor to firmly adhere to the surface of the oxide film, forming a protective barrier. In the process of hydrogen ions moving to the surface of carbon steel, they will interact with the corrosion inhibitor molecules, and their penetration path will be blocked, and they cannot smoothly reach the surface of carbon steel to participate in the corrosion reaction, thereby weakening the galvanic cell effect and slowing down the corrosion of the sample.

[0046] From the perspective of surface properties, the surface charge state of iron oxide is special, and the positively charged sites on its surface are conducive to the effective adsorption of corrosion inhibitors by electrostatic action; at the same time, the abundant active sites such as lattice defects and oxygen vacancies can undergo specific chemical reactions or form chemical bonds with functional groups such as hydroxyl groups of the corrosion inhibitor, thereby firmly attaching. At the chemical reaction level, the corrosion inhibitor can further react with iron oxide to form a stable and dense protective film that effectively blocks the corrosive medium. In terms of adsorption, the corrosion inhibitor can be adsorbed on the surface of iron oxide in a way that is conducive to the formation of a complete and tight adsorption layer, such as through the combination of multiple hydroxyl groups with different sites to form a network structure, which greatly enhances the corrosion inhibition performance.

[0047] Example 1

[0048] A corrosion inhibition film based on a composite film layer is prepared by the following steps:

[0049] (1) Prepare L245 carbon steel specimens and cut their wire electrodes into 19 mm discs;

[0050] (2) The small disc was polished with 400#, 1000#, 1500#, 2000#, and 3000# sandpaper in sequence, and then its surface was polished to mirror smoothness (using silica polishing liquid with a particle size of 0.5-1.0 μm), and finally ultrasonically cleaned in acetone, ethanol, and distilled water for 1 min in sequence;

[0051] (3) dissolving 4.2 g of a passivating agent (sodium molybdate) in 100 mL of water, and adjusting the pH to 5.8 using a pH adjusting agent (a standard mixed solution of sodium dihydrogen phosphate and disodium hydrogen phosphate) to obtain a passivating agent concentrate;

[0052] (4) obtaining 500 mL of corrosive formation water, and passing a mixed gas of carbon dioxide and oxygen (the gas pressure ratio of carbon dioxide to oxygen is 9:1) into the corrosive formation water for 24 hours, and then adding 20 mL of the passivator concentrate, stirring evenly, to obtain a passivator solution;

[0053] In this embodiment, the corrosive formation water is simulated formation water from an oil field in Northwest China, and its composition is shown in Table 1:

[0054] Table 1 Simulated formation water composition

[0055] Element NaCl <![CDATA[CaCl 2 ]]> <![CDATA[MgCl 2 ]]> <![CDATA[Na 2 SO 4 ]]> <![CDATA[NaHCO 3 ]]> <![CDATA[CO 2 ]]> <![CDATA[O 2 ]]> content 20.57g / L 1.34g / L 0.31g / L 0.04g / L 1.11g / L 27mg / L 3mg / L

[0056] (5) placing the carbon steel sample treated in step (2) in the passivating agent solution and passivating at 40° C. for 6 hours to form a passivation film layer on the carbon steel sample;

[0057] (6) A 100 ppm corrosion inhibitor solution (the corrosion inhibitor is glycolic acid) is prepared, and the carbon steel sample covered with the passivation layer is immersed in the corrosion inhibitor solution at 40° C. for 36 hours, so that the carbon steel sample with the passivation film layer is further covered with the corrosion inhibitor layer to obtain a corrosion inhibition film of a composite film layer.

[0058] Example 2

[0059] Different from Example 1, the corrosion inhibitor in step (6) of this example is 6-hydroxyhexanoic acid.

[0060] Example 3

[0061] Different from Example 1, the corrosion inhibitor in step (6) of this example is 10-hydroxydecanoic acid.

[0062] Comparative Example 1

[0063] Different from Example 1, this comparative example does not include steps (3) to (6), that is, the carbon steel sample contains neither a passivation layer nor a corrosion inhibitor layer.

[0064] Comparative Example 2

[0065] Different from Example 1, this comparative example does not include step (6), that is, the carbon steel sample only includes a passivation layer.

[0066] Comparative Example 3

[0067] Different from Example 1, the corrosion inhibitor in step (6) of this comparative example is 2-mercaptopyrimidine.

[0068] Test Case

[0069] The finished products of each embodiment and each comparative example were subjected to electrochemical impedance spectroscopy test. The test method was as follows: first, the simulated formation water was heated to 40°C in a water bath, and then the corresponding mixed gas was introduced until saturated, and then the working electrode, the reference electrode, and the counter electrode were immersed in the corrosion solution. After the open circuit potential was basically stable, the electrochemical impedance spectroscopy test was performed. The test frequency range was 0.01 to 10 5 Hz, with an amplitude of 5 mV. The electrochemical impedance test results of each embodiment and each comparative example are shown in Table 2:

[0070] Table 2 Electrochemical impedance test results of each embodiment and each comparative example

[0071] Corrosion Inhibitor Film <![CDATA[R s (Ωcm 2 )]]> n <![CDATA[R f (Ωcm 2 )]]> n <![CDATA[R ct / R L / R w (Ωcm 2 )]]> <![CDATA[R p (Ωcm 2 )]]> Comparative Example 1 8.816 0.7959 161.50 - 473.80 635.30 Comparative Example 2 14.15 0.7507 32.94 0.7572 12340.00 12372.94 Comparative Example 3 14.23 0.7736 28.90 0.7457 12760.00 12788.90 Example 1 12.12 0.8624 13.77 0.6984 14480.00 14493.77 Example 2 15.14 0.5728 55.78 0.8514 16020.00 16075.78 Example 3 12.09 0.7738 26.80 0.7063 18740.00 18766.80

[0072] As can be seen from Table 2, although only the passivation treatment of Comparative Example 2 can improve the corrosion protection performance of the carbon steel sample, it is not as obvious as the improvement of the corrosion inhibition film based on the composite film layer of the present invention. The corrosion inhibition effect of the present invention is significantly improved, and the corrosion inhibitor of the present invention increases with the increase of the molecular chain length, and the impedance value is also significantly improved, indicating that its corrosion inhibition effect is enhanced with the increase of the chain length. In Examples 1-3, the effect of 10-hydroxydecanoic acid is the most significant, and its impedance value is the highest, indicating that it is the most effective in providing corrosion protection. In addition, when other corrosion inhibitors such as 2-mercaptopyrimidine are used, the effect is not obvious, and compared with only the passivation treatment, the impedance value is almost not significantly improved, which shows that the corrosion inhibition effect of using 2-mercaptopyrimidine as a corrosion inhibitor on the passivation film is limited.

[0073] In addition, based on Figure 2 The equivalent circuit model shown is used to fit and analyze the electrochemical impedance spectroscopy data. In an oxygen-containing environment, the adsorption / desorption process of redox mediators or the formation of an intermediate product layer may occur on the electrode surface, resulting in the appearance of inductive reactance characteristics (usually manifested as a negative imaginary part in the Nyquist diagram). Therefore, an inductor element (L) needs to be introduced into the equivalent circuit to characterize this type of kinetic behavior.

[0074] For the working electrode of the passivation system, the interfacial mass transfer process presents significant characteristics: when the metal enters the passivation state, the formation of a dense oxide film on the surface will significantly change the mass transfer rate and distribution state of hydrogen ions and dissolved oxygen to the electrode surface. In order to accurately describe this restricted diffusion process, the Warburg diffusion impedance (Zw) or the finite layer diffusion element (usually characterized by the diffusion resistance Rw) needs to be introduced into the equivalent circuit.

[0075] In the corrosion system containing corrosion inhibitors, a typical three-component equivalent circuit model (Rs-(Rf / / CPEf)-(Rct / / CPEdl)) is used for fitting analysis, where Rs represents the solution resistance, Rf characterizes the film resistance of the corrosion inhibitor adsorption layer or corrosion product, and Rct reflects the charge transfer resistance.

[0076] Through parameter analysis, it can be known that the polarization resistance Rp (Rp = Rf + Rct) comprehensively characterizes the total resistance of the electrode reaction, and its value is inversely proportional to the corrosion current density (following the Stern-Geary equation: Icorr = B / Rp, B is the Stern-Geary constant). Therefore, the change in the Rp value can effectively reflect the synergistic inhibition of the corrosion inhibitor on the interfacial charge transfer process and mass transfer kinetics, and becomes a key quantitative indicator for evaluating the protective performance of the corrosion inhibitor.

[0077] in accordance with Figure 2 The circuit diagram shown is fitted to the electrochemical data, and the results are as follows Figure 3 As shown. Figure 3 It can be seen that under blank conditions (Blank), the corrosion of the material is extremely serious. At this time, the polarization resistance (R p ) is only 635.30(Ωcm 2 ), which indicates that without any protective measures, the material and the substances in the environment have a strong electrochemical reaction, resulting in rapid corrosion. After passivation treatment (passivation 6h+passivation 36h), the corrosion of carbon steel has been greatly improved. The polarization resistance (R p ) increased significantly to 12372.94(Ωcm 2 ), indicating that the passivation treatment formed an effective protective film on the surface of the material, which significantly inhibited the corrosion reaction. The effects of different corrosion inhibitors on the properties of the materials after passivation were further studied. On the basis of only passivation for 6h, 2-MP corrosion inhibitor was added (passivation 6h+2-MP 36h), and it was found that the corrosion inhibition performance was almost unchanged. Its polarization resistance value is similar to that of the passivation group only, indicating that the corrosion inhibition effect of 2-MP corrosion inhibitor on the passivated material in this system is not obvious. However, when hydroxycarboxylic acid corrosion inhibitors are added (such as passivation 6h+6-Hydroxyhexanoic acid 36h and passivation 6h+10-Hydroxydecanoic acid 36h), the corrosion inhibition performance is significantly improved. Moreover, with the increase of the carbon chain of hydroxycarboxylic acid (from ethanolic acid to 10-hydroxydecanoic acid), the value of polarization resistance gradually increases, which is 14493.77 (Ωcm 2 )、16075.78(Ωcm 2 ) and 18766.80(Ωcm 2 ). This shows that hydroxycarboxylic acid corrosion inhibitors with longer carbon chains can be more effectively adsorbed on the surface of the material, further enhancing the stability and protective properties of the passivation film, thereby improving the corrosion resistance of the material. In summary, passivation treatment plus corrosion inhibitor is a good way to improve the material's resistance to CO 2 -O 2 The reasonable selection of corrosion inhibitors, especially hydroxycarboxylic acid corrosion inhibitors, can further optimize the corrosion inhibition performance of materials.

[0078] In summary, the present invention has an extremely excellent anti-corrosion effect and can effectively inhibit corrosion in a simulated air flooding environment, thereby providing a reliable corrosion protection guarantee for the application of related materials in this specific environment. Compared with the prior art, the present invention has significant progress.

[0079] The above description is only a representative embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, uses the above-disclosed technical contents to make some changes or modifications to the embodiments are equivalent embodiments of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a corrosion inhibition film based on a composite film layer, characterized in that: The following steps are involved: S1: preparing a carbon steel sample and pretreating the carbon steel sample; S2: dissolving the passivating agent in water, and adjusting the pH to 5-6.5 by a pH adjusting agent to obtain a passivating agent concentrate with a concentration of 0.2-0.325M; S3: preparing simulated formation water, introducing a mixed gas of carbon dioxide and oxygen into the simulated formation water, and then adding the passivating agent concentrate in a volume ratio of 1:25, stirring evenly, to obtain a passivating agent solution; S4: placing the pretreated carbon steel sample in the passivating agent solution for passivation at 30-50° C. for 4-8 hours, so that a passivation film layer is formed on the carbon steel sample; S5: Prepare a 100 ppm corrosion inhibitor solution, and add the corrosion inhibitor solution to the solution of step S4, adsorb at 30-50°C for 12-36 hours, so that the carbon steel sample with the passive film layer is covered with a corrosion inhibitor layer to obtain a composite corrosion inhibition film.

2. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 1, characterized in that: In step S1, the pretreatment includes grinding, polishing, cleaning and drying processes performed in sequence.

3. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 2, characterized in that: When performing the polishing process, mechanical polishing and / or chemical polishing are used.

4. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 2, characterized in that: When cleaning, acetone, ethanol and distilled water are used for ultrasonic treatment in sequence.

5. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 1, characterized in that: In step S2, the passivating agent is any one of sodium molybdate, sodium tungstate, and potassium permanganate.

6. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 1, characterized in that: In step S2, the pH adjuster is a standard mixed solution of sodium dihydrogen phosphate and disodium hydrogen phosphate.

7. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 1, characterized in that: In step S3, in the mixed gas, the gas pressure ratio of carbon dioxide is 90%, and the gas pressure ratio of oxygen is 10%.

8. The method for preparing a corrosion inhibition film based on a composite film layer according to any one of claims 1 to 7, characterized in that: In step S5, the corrosion inhibitor in the corrosion inhibitor solution is a straight-chain compound containing hydroxyl groups and carboxyl groups.

9. The method for preparing a corrosion-inhibiting film based on a composite film layer according to claim 8, characterized in that: The corrosion inhibitor is any one or more of glycolic acid, 3-hydroxypropionic acid, 4-hydroxybutyric acid, 6-hydroxyhexanoic acid, 7-hydroxyheptanoic acid, 8-hydroxyoctanoic acid, 9-hydroxynonanoic acid, and 10-hydroxydecanoic acid.

10. A corrosion inhibition film based on a composite film layer, characterized in that: The corrosion-inhibiting film is prepared by the method for preparing a corrosion-inhibiting film based on a composite film layer as described in any one of claims 1 to 9.

Images