Preparation method of corrosion inhibitor

Abstract

The invention relates to a preparation method of a corrosion inhibitor, and the method comprises the following steps: providing plant raw materials which are treated to be dry, and the plant raw materials comprise moso bamboo leaves, guava leaves and marigold; the moso bamboo leaves and the guava leaves are smashed and then subjected to ultrasonic extraction with a first alcohol solvent, and a first extracting solution is obtained; crushing the marigold, and performing supercritical CO2 extraction by taking a second alcohol solvent as a cosolvent to obtain a second extracting solution; mixing the first extracting solution and the second extracting solution to obtain a plant extracting solution; and mixing the plant extract, the corrosion inhibition synergist and the alcohol-water solution to obtain the corrosion inhibitor. Main active substances of the corrosion inhibitor can be degraded, and the corrosion inhibitor is environmentally friendly and has excellent corrosion inhibition capacity.

Description

Technical Field

[0001] This application relates to the field of materials, and particularly to metal-organic framework materials. Background Art

[0002] In the surface gathering and transportation systems of oil and gas fields and gas storage reservoirs, serious metal corrosion problems often occur. Using corrosion inhibitors is the most common and economical method for metal anti-corrosion. They are easy to use and can achieve good corrosion inhibition effects even at low concentrations, thus attracting wide attention.

[0003] Commonly used corrosion inhibitors can be divided into two types according to their chemical structures: inorganic corrosion inhibitors and organic corrosion inhibitors. In inorganic corrosion inhibitors, the atoms with high electronegativity usually play the role of corrosion inhibition, such as phosphorus, sulfur, nitrogen, oxygen, etc., and salts containing strongly oxidizing ions, such as arsenates, phosphates, and chromates. Organic corrosion inhibitors containing organic heterocyclic compounds with unsaturated bonds or large conjugated systems, such as amides, Schiff bases, and pyridines, although they have good corrosion inhibition efficiency, their synthesis routes are complex, the prices are high, they are not biodegradable, usually toxic, and extensive use is likely to damage water bodies, cause red tides and algal blooms, resulting in eutrophication of water bodies, and also damage the soil environment. Therefore, it is necessary to find corrosion inhibitors with high corrosion inhibition efficiency and environmental friendliness.

[0004] Plant corrosion inhibitors refer to corrosion inhibitors whose active corrosion inhibition components are mainly plant extracts. They have the advantages of not involving complex chemical synthesis, usually being biodegradable, and being environmentally friendly. However, at present, the corrosion inhibition performance of plant corrosion inhibitors is difficult to compare with that of traditional corrosion inhibitors, and the corrosion inhibition ability needs to be improved. Summary of the Invention

[0005] The embodiments of this application provide a preparation method of a corrosion inhibitor to solve the technical problem that the current plant corrosion inhibitors have insufficient corrosion inhibition performance.

[0006] The embodiments of this application provide a preparation method of a corrosion inhibitor, and the method includes the following steps:

[0007] Provide plant raw materials processed until dry, and the plant raw materials include Phyllostachys heterocycla leaves, Psidium guajava leaves, and Tagetes erecta;

[0008] After crushing the Phyllostachys heterocycla leaves and the Psidium guajava leaves, perform ultrasonic extraction with a first alcohol solvent to obtain a first extract;

[0009] After crushing the Tagetes erecta, use a second alcohol solvent as a co-solvent for supercritical CO 2 extraction to obtain a second extract;

[0010] Mix the first extract and the second extract to obtain a plant extract;

[0011] Mix the plant extract, corrosion inhibitor synergist, and alcohol aqueous solution to obtain the corrosion inhibitor.

[0012] In some embodiments of the present application, the ultrasonic extraction includes the following steps:

[0013] Add the crushed bamboo leaves and guava leaves to the first alcohol solvent, soak for a predetermined time to obtain a premix;

[0014] After subjecting the premix to ultrasonic treatment, filter to obtain a first filtrate;

[0015] Concentrate the first filtrate to obtain the first extract.

[0016] In some embodiments of the present application, the mass ratio of the total weight of the bamboo leaves and guava leaves to the mass of the first alcohol solvent is 1:9 to 12; and / or,

[0017] The predetermined time is 30 to 40 h; and / or,

[0018] The duration of the ultrasonic treatment is not less than 30 min.

[0019] In some embodiments of the present application, the volume ratio of the first filtrate to the first extract is 1:0.3 to 0.4;

[0020] The second extract does not contain the second alcohol solvent.

[0021] In some embodiments of the present application, the first alcohol solvent is at least one of methanol, ethanol, n-propanol, and isopropanol; and / or,

[0022] The second alcohol solvent is at least one of methanol, ethanol, n-propanol, and isopropanol.

[0023] In some embodiments of the present application, the alcohol aqueous solution is an ethanol aqueous solution of 75 wt% to 80 wt%.

[0024] In some embodiments of the present application, based on dry weight, the ratio of bamboo leaves, guava leaves, and marigolds in the plant raw material is 3 to 6:2 to 8:3 to 10.

[0025] In some embodiments of the present application, the corrosion inhibitor synergist includes amide-based gemini quaternary ammonium salts, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0026] In some embodiments of the present application, in the corrosion inhibitor synergist, the mass ratio of amide-based gemini quaternary ammonium salts, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 15 to 30:9 to 40:12 to 25.

[0027] In some embodiments of the present application, the mass ratio of the plant extract, the corrosion inhibitor synergist, and the aqueous alcohol solution is 15-18:10-13:20-40.

[0028] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0029] The preparation method of the corrosion inhibitor provided by the embodiments of the present application selects three plant tissues, namely, Phyllostachys heterocycla leaves, Psidium guajava leaves, and Tagetes erecta, and uses ultrasonic extraction and supercritical CO 2 extraction. In the case of only selecting alcohol solvents, the effective components in Phyllostachys heterocycla leaves, Psidium guajava leaves, and Tagetes erecta are extracted, and are compounded with a corrosion inhibitor synergist and an aqueous alcohol solution to obtain a corrosion inhibitor. The preparation process does not involve complex chemical synthesis. The main active substances of the obtained corrosion inhibitor are degradable, environmentally friendly, and have excellent corrosion inhibition ability. Description of the Drawings

[0030] The drawings herein are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 It is the polarization curve of the corrosion of L485M steel in the corrosion solution with different concentrations of the corrosion inhibitor;

[0033] Figure 2 It is the corrosion morphology of the L485M steel sample in the corrosion solution without adding the corrosion inhibitor;

[0034] Figure 3 It is the corrosion morphology of the L485M steel sample in the corrosion solution with a corrosion inhibitor concentration of 100 ppm;

[0035] Figure 4 It is the electrochemical impedance spectroscopy diagram of the corrosion of L485M steel in the corrosion solution with different concentrations of the corrosion inhibitor. Detailed Embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0037] Unless otherwise specifically stated, the terms used in this document should be understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs. In case of any conflict, this specification shall prevail.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in this application can all be obtained through market purchases or can be prepared by existing methods.

[0039] There is a technical problem that the existing plant corrosion inhibitors have insufficient corrosion inhibition performance.

[0040] The technical solutions provided by the embodiments of this application to solve the above technical problems are generally as follows:

[0041] The embodiments of this application provide a preparation method of a corrosion inhibitor, and the method includes the following steps:

[0042] S1: Provide plant raw materials processed to be dry, and the plant raw materials include Phyllostachys heterocycla cv. Pubescens leaves, Psidium guajava leaves, and Tagetes erecta;

[0043] S2: After crushing the Phyllostachys heterocycla cv. Pubescens leaves and the Psidium guajava leaves, perform ultrasonic extraction with a first alcohol solvent to obtain a first extract;

[0044] S3: After crushing the Tagetes erecta, use a second alcohol solvent as a co-solvent for supercritical CO 2 extraction to obtain a second extract;

[0045] S4: Mix the first extract and the second extract to obtain a plant extract;

[0046] S5: Mix the plant extract with a corrosion inhibition synergist and an alcohol aqueous solution to obtain the corrosion inhibitor.

[0047] Those skilled in the art can obtain plant raw materials processed to be dry through common general knowledge. As an example, the plant raw materials processed to be dry described in this application can be prepared in the following manner: After collecting fresh Phyllostachys heterocycla cv. Pubescens leaves, Psidium guajava leaves, and Tagetes erecta, wash and dry them to obtain the plant raw materials processed to be dry.

[0048] The first extract described in this application can be a solution containing a first alcohol solvent, as well as extracts of Phyllostachys heterocycla leaves and Psidium guajava leaves, or it can be an extract of Phyllostachys heterocycla leaves and Psidium guajava leaves without the first alcohol solvent. The extracts of Phyllostachys heterocycla leaves and Psidium guajava leaves mainly include orientin and other flavonoid compounds.

[0049] Similarly, the second extract described in this application can be a solution containing a second alcohol solvent, as well as an extract of Tagetes erecta, or it can be an extract of Tagetes erecta without the second alcohol solvent. The extract of Tagetes erecta mainly includes zeaxanthin and zeaxanthin derivatives.

[0050] The first alcohol solvent and the second alcohol solvent can be selected from conventional alcohol solvents in the art.

[0051] The ultrasonic extraction described in this application refers to adding crushed Phyllostachys heterocycla leaves and Psidium guajava leaves to the first alcohol solvent and then treating with ultrasonic waves. Through ultrasonic extraction, more effective substances in plants can be released in a short time, accelerating the release, dissolution, and diffusion of effective substances in cells. And the ultrasonic extraction step of this application only involves alcohol solvents, which is more environmentally friendly.

[0052] Supercritical CO 2 Extraction is a conventional extraction method in the art. This application selects ultrasonic CO 2 Extraction, which can be carried out near room temperature (35 - 40 °C) and under the shroud of CO 2 gas, effectively preventing the oxidation and volatilization of thermosensitive substances. It can extract the corrosion inhibitor components we need in plants more completely and effectively. The co-solvent is selected as the second alcohol solvent, and it does not involve organic reagents with high pollution.

[0053] By selecting three plant tissues of Phyllostachys heterocycla leaves, Psidium guajava leaves, and Tagetes erecta, and using ultrasonic extraction and supercritical CO 2 Extraction, under the condition of only selecting alcohol solvents, the effective components in Phyllostachys heterocycla leaves, Psidium guajava leaves, and Tagetes erecta are extracted, and then compounded with a corrosion inhibitor synergist and an alcohol aqueous solution to obtain a corrosion inhibitor. The preparation process does not involve complex chemical synthesis. The main active substances of the obtained corrosion inhibitor are degradable, environmentally friendly, and have excellent corrosion inhibition ability.

[0054] In some embodiments of this application, the ultrasonic extraction includes the following steps:

[0055] S21: Add crushed Phyllostachys heterocycla leaves and Psidium guajava leaves to the first alcohol solvent, soak for a predetermined time to obtain a premix;

[0056] S22: After ultrasonic treatment of the premix, filter to obtain a first filtrate;

[0057] S23: Concentrate the first filtrate to obtain the first extract.

[0058] The concentrated first filtrate refers to removing a part of the first alcohol solvent. The removal method can be, for example, heating evaporation or vacuum evaporation.

[0059] In some embodiments of the present application, the mass ratio of the total weight of the bamboo leaves of Phyllostachys pubescens and the guava leaves to the mass of the first alcohol solvent is 1:9 to 12; and / or,

[0060] The predetermined time is 30 to 40 h; and / or,

[0061] The duration of the ultrasonic treatment is not less than 30 min.

[0062] Limiting the mass ratio of the bamboo leaves of Phyllostachys pubescens, guava leaves to the first alcohol solvent within the above range can, on the one hand, fully extract the active substances in the bamboo leaves of Phyllostachys pubescens and guava leaves, and on the other hand, minimize the total amount of the first alcohol solvent, avoiding excessive time consumption for concentrating the first filtrate and wasting raw materials in step S23.

[0063] In some embodiments of the present application, the volume ratio of the first filtrate to the first extract is 1:0.3 to 0.4;

[0064] The second extract does not contain the second alcohol solvent.

[0065] It is easy to understand that the reduced volume of the first extract compared to the first filtrate is the amount of the first alcohol solvent reduced during the concentration process.

[0066] The marigold extract is mainly zeaxanthin and zeaxanthin derivatives, which have a large difference in boiling point from the second alcohol solvent and are easily completely separated.

[0067] In some embodiments of the present application, the first alcohol solvent is at least one of methanol, ethanol, n-propanol, and isopropanol; and / or,

[0068] The second alcohol solvent is at least one of methanol, ethanol, n-propanol, and isopropanol.

[0069] The above solvents are common and easily obtainable alcohol solvents in the art, are more environmentally friendly, and have good extraction ability for the active substances in the bamboo leaves of Phyllostachys pubescens, guava leaves, and marigold.

[0070] In some embodiments of the present application, the aqueous alcohol solution is an ethanol aqueous solution of 75 wt% to 80 wt%.

[0071] In some embodiments of the present application, based on dry weight, the ratio of the bamboo leaves of Phyllostachys pubescens, guava leaves, and marigold in the plant raw material is 3 to 6:2 to 8:3 to 10.

[0072] In some embodiments of the present application, the corrosion inhibitor synergist includes amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0073] The beneficial effect of selecting the above components as the corrosion inhibitor is to enhance the adsorption capacity of the plant extract and improve the corrosion inhibition effect.

[0074] In some embodiments of the present application, in the corrosion inhibitor synergist, the mass ratio of amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 15-30:9-40:12-25.

[0075] In some embodiments of the present application, the mass ratio of the plant extract, the corrosion inhibitor synergist, and the aqueous alcohol solution is 15-18:10-13:20-40.

[0076] The following further elaborates the present application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are generally determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0077] Example 1

[0078] This example provides a preparation method of a corrosion inhibitor, and the method includes the following steps:

[0079] Sa: Provide plant raw materials processed to dryness, and the plant raw materials include Phyllostachys heterocycla var. pubescens leaves, Psidium guajava leaves, and Tagetes erecta, and in terms of dry weight, the ratio of Phyllostachys heterocycla var. pubescens leaves, Psidium guajava leaves, and Tagetes erecta is 15:15:28;

[0080] Sb: Mix the crushed Phyllostachys heterocycla var. pubescens leaves and Psidium guajava leaves to obtain a mixed crushed material, and mix the mixed crushed material with ethanol in a ratio of 1:10, and soak for 36 h to obtain a premix;

[0081] Sc: After performing ultrasonic treatment on the premix for 30 min, filter to obtain a first filtrate;

[0082] Sd: Concentrate the first filtrate to reduce the volume of the first filtrate by two-thirds to obtain a first extract;

[0083] Se: After crushing the Tagetes erecta, use ethanol as a cosolvent for supercritical CO 2 extraction to obtain a second extract, wherein the second extract is a pure Tagetes erecta extract and does not contain the second alcohol solvent;

[0084] Sf: Mix the first extract and the second extract to obtain a plant extract;

[0085] Sg: Provide a corrosion inhibitor synergist, which includes amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid with a mass ratio of 15:10:16;

[0086] Sh: Mix the plant extract, the corrosion inhibitor synergist, and an ethanol aqueous solution of 78 wt% according to a mass ratio of 16:13:30 to obtain the corrosion inhibitor.

[0087] Example 2

[0088] The difference between this example and Example 1 is only that:

[0089] In step Sa, the ratio of Phyllostachys heterocycla cv. pubescens leaves, Psidium guajava leaves, and Tagetes erecta is 23:20:35;

[0090] In step Sg, the mass ratio of amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 36:40:45;

[0091] In step Sh, the mass ratio of the plant extract, the corrosion inhibitor synergist, and the ethanol aqueous solution is 20:12:25.

[0092] Example 3

[0093] The difference between this example and Example 1 is only that:

[0094] In step Sa, the ratio of Phyllostachys heterocycla cv. pubescens leaves, Psidium guajava leaves, and Tagetes erecta is 35:28:45;

[0095] In step Sg, the mass ratio of amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 36:40:45;

[0096] In step Sh, the mass ratio of the plant extract, the corrosion inhibitor synergist, and the ethanol aqueous solution is 22:13:24.

[0097] Example 4

[0098] The difference between this example and Example 1 is only that:

[0099] In step Sa, the ratio of Phyllostachys heterocycla cv. pubescens leaves, Psidium guajava leaves, and Tagetes erecta is 35:42:65;

[0100] In step Sg, the mass ratio of amido gemini quaternary ammonium salt, sodium dodecylbenzenesulfonate, and 2-phosphonobutane-1,2,4-tricarboxylic acid is 50:70:45;

[0101] In step Sh, the mass ratio of the plant extract, the corrosion inhibitor synergist, and the ethanol aqueous solution is 30:13:30.

[0102] Relevant experiments and effect data:

[0103] The performance of the composite corrosion inhibitors in Examples 1 to 4 was tested and evaluated using the common corrosion inhibition efficiency experimental method (weight loss method). The method outline is as follows: The corrosion solution is saturated CO 2 simulated oilfield produced water, the components are shown in Table 1 below, the corrosion temperature is 35°C, and the pressure is normal.

[0104]

[0105] Table 1

[0106] Taking the commonly used L485M steel sheet in oil and gas fields as the corrosion object, the L48M steel is cut into metal specimens of 50mm×10mm×3mm. The specimens are polished with water sandpaper until the surface is mirror-smooth, then washed with deionized water, acetone, and absolute ethanol, and dried before weighing. The specimens are immersed in the corrosion solution with a corrosion inhibitor concentration of 100 ppm for a three-day weight loss experiment. Under the same conditions, the mass difference of the specimens in Examples 1 to 4 before and after corrosion is calculated, and the corrosion inhibitor efficiency is calculated. The results are expressed as mass percentages, as shown in Table 2 below. The average corrosion rate of the specimens can be calculated using the weight loss method. The calculation formula is:

[0107]

[0108] In the formula, v is the corrosion rate, mm / y; M is the mass of the specimen before the experiment, g; M 1 is the mass of the specimen after the experiment, g; S is the total area of the specimen, cm 2 ; t is the experimental time, h; D is the density of the material, kg / m 3 . The metal material under study is L485M steel, and the density is 7850 kg / m 3 .

[0109] The calculation formula for the corrosion inhibition efficiency of the corrosion inhibitor:

[0110]

[0111] In the formula, η is the corrosion inhibition efficiency, %; v 0 , v inh are the corrosion rates before and after adding the corrosion inhibitor, respectively, mm / y.

[0112] The obtained corrosion inhibition efficiencies are shown in Table 2.

[0113] Example Agent Concentration (ppm) Corrosion Inhibition Rate (%) Example 1 100 80.84％ Example 2 100 84.98％ Example 3 100 91.87％ Example 4 100 93.31％

[0114] Table 2

[0115] From the experimental results of Comparative Examples 1 to 4, it can be seen that the environmentally friendly corrosion inhibitor for oil and gas fields shows good corrosion inhibition performance as a whole. The composite corrosion inhibitor component ratio in Example 4 is the optimal ratio.

[0116] The present invention uses electrochemistry methods (including electrochemical impedance and electrochemical polarization), and corrosion morphology observation and analysis to conduct the following research on the corrosion resistance of the environmentally friendly corrosion inhibitor for oil and gas fields prepared in Example 4:

[0117] ① Electrochemical test: Cut the L485M steel into square metal blocks with dimensions of 10 mm × 10 mm × 3 mm. After grinding the surface, use AB glue, soldering, and copper wire to make a working electrode. The electrochemical experiment uses a traditional three-electrode system and is carried out on an electrochemical workstation. The experimental data is processed in the CS Studio5 software. The working electrode is made of L485M steel, the reference electrode is a saturated calomel electrode, and the auxiliary electrode is a platinum electrode. The experiment is carried out in a 35 °C constant temperature water bath. The inhibitor concentration is expressed as the volume ratio between the inhibitor and the corrosion solution. When testing the polarization curve, the scanning potential range is set to ±200 mV relative to the open circuit potential, and the potentiodynamic scanning rate is set to 0.1667 mV / s. Then, the required relevant parameters are obtained through the Tafel traditional fitting method. The corrosion inhibition efficiency (η) is obtained from the following formula:

[0118]

[0119] In the formula, η is the corrosion inhibition efficiency, %; and I corr are the corrosion current densities before and after adding the corrosion inhibitor, respectively, μA / cm 2 .

[0120] ② Surface morphology observation: The size of the L485M steel sample for morphology observation is 50 mm × 10 mm × 3 mm. After grinding to a bright surface, it is dynamically corroded in the corrosion solution without and with the corrosion inhibitor for 48 hours at a corrosion temperature of 35 °C. After taking it out and drying, a digital camera is used to take pictures to observe its corrosion morphology. Figure 1 is the polarization curve of the L485M steel in the corrosion solution with different concentrations (0 - 100 ppm) of the corrosion inhibitor. After adding the corrosion inhibitor, the corrosion potential shifts positively, and both the cathode part and the anode part of the curve move towards the low current value direction, indicating that the reactions at both the anode and cathode are effectively inhibited. From the fitting of the figure, the corrosion potential E corr , the corrosion current density I corr , the anodic Tafel slope B a and the cathodic Tafel slope B c and other electrochemical parameters can be obtained. The calculation results are shown in

[0121] Table 3.

[0122]

[0123]

[0124] Table 3

[0125] The corrosion inhibition rate in Table 3 shows an obvious trend of increasing with the increase of the corrosion inhibitor concentration.

[0126] Figure 3 and Figure 4 are the corrosion morphologies of the L485M steel specimens after 48 hours of corrosion in the corrosion solution without adding a corrosion inhibitor and in the corrosion solution with a corrosion inhibitor concentration of 100 ppm, respectively. The corrosion condition in the corrosion solution without adding a corrosion inhibitor is more serious, and more granular corrosion products are formed and attached to the metal surface. While the corrosion degree of the L485M steel in the corrosion solution after adding a corrosion inhibitor is lighter, the metal surface is smooth and bright, and no obvious corrosion phenomenon occurs, indicating that the corrosion inhibitor can effectively inhibit the corrosion of the L485M steel in the corrosion solution.

[0127] Figure 2 is the electrochemical impedance spectrum of the L485M steel in the corrosion solution with different concentrations (0 - 100 ppm) of the corrosion inhibitor. The curvature radius of the capacitive reactance arc in the high-frequency region first increases and then decreases with the increase of the corrosion inhibitor concentration, indicating that with the increase of the corrosion inhibitor concentration, the anti-corrosion layer formed by the adsorption of the corrosion inhibitor molecules on the surface of the L485M steel becomes more complete, and the charge transfer resistance gradually increases. However, when the addition amount of the corrosion inhibitor is too high, it will have an adverse effect on the adsorption of the corrosion inhibitor molecules. The equivalent circuit diagram is used to fit the EIS parameters, and the fitted parameters are shown in Table 4.

[0128] The corrosion inhibition formula is as follows:

[0129] In the formula: η, corrosion inhibition efficiency, %; R ct are the charge transfer resistances before and after adding the corrosion inhibitor, respectively, Ω·cm 2 .

[0130]

[0131]

[0132] Table 4

[0133] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0134] In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the drawings. Additionally, in the description of the specification of the present application, the terms "include", "comprise", etc. mean "including but not limited to". Moreover, the term "include", "comprise", or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such a process, method, article, or device. Without further limitation, the elements defined by the statement "including..." do not exclude the existence of additional identical elements in the process, method, article, or device including the said elements. In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that these three associated objects can exist alone for any one item, or any at least two of them exist simultaneously. For example, for A, and / or B, and / or C, it can represent that any one of A, B, and C exists alone, or any two of them exist simultaneously, or all three of them exist simultaneously. In this article, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)", or similar expressions refer to any combination of these items, including any combination of single (item) or plural (items). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0135] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a corrosion inhibitor, characterized in that: The method comprises the following steps: Providing plant materials that have been processed to dryness, wherein the plant materials include bamboo leaves, guava leaves, and marigolds; The moso bamboo leaves and the guava leaves are crushed and then subjected to ultrasonic extraction with a first alcohol solvent to obtain a first extract; After crushing the marigold, supercritical CO2 extraction is performed using a second alcohol solvent as a co-solvent to obtain a second extract; Mixing the first extract and the second extract to obtain a plant extract; The plant extract, the corrosion inhibitor and the alcohol aqueous solution are mixed to obtain the corrosion inhibitor.

2. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: The ultrasonic extraction comprises the following steps: Adding crushed bamboo leaves and guava leaves into a first alcohol solvent and soaking for a predetermined time to obtain a premix; After subjecting the premix to ultrasonic treatment, filtering to obtain a first filtrate; The first filtrate is concentrated to obtain the first extract.

3. The method for preparing the corrosion inhibitor according to claim 2, characterized in that: The mass ratio of the total weight of the bamboo leaves and the guava leaves to the first alcohol solvent is 1:9-12; and / or, The predetermined time is 30 to 40 hours; and / or, The duration of the ultrasonic treatment is not less than 30 min.

4. The method for preparing the corrosion inhibitor according to claim 3, characterized in that: The volume ratio of the first filtrate to the first extract is 1:0.3-0.4; The second extract does not contain the second alcohol solvent.

5. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: The first alcohol solvent is at least one of methanol, ethanol, n-propanol and isopropanol; and / or, The second alcohol solvent is at least one of methanol, ethanol, n-propanol and isopropanol.

6. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: The alcohol aqueous solution is 75wt% to 80wt% ethanol aqueous solution.

7. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: Calculated by dry weight, in the plant raw materials, the ratio of bamboo leaves, guava leaves and marigold is 3-6:2-8:3-10.

8. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: The corrosion inhibitor and synergist include amide-based gemini quaternary ammonium salt, sodium dodecylbenzene sulfonate, and 2-phosphonobutane-1,2,4-trihydroxy acid.

9. The method for preparing the corrosion inhibitor according to claim 8, characterized in that: In the corrosion inhibitor and synergist, the mass ratio of amide gemini quaternary ammonium salt, sodium dodecylbenzene sulfonate and 2-phosphonobutane-1,2,4-trihydroxy acid is 15-30:9-40:12-25.

10. The method for preparing the corrosion inhibitor according to claim 1, characterized in that: The mass ratio of the plant extract, the corrosion inhibitor and the alcohol aqueous solution is 15-18:10-13:20-40.

Images