Preparation method and application of composite cation corrosion inhibitor based on critical micelle concentration regulation and control

Abstract

The invention discloses a composite cation corrosion inhibitor based on critical micelle concentration regulation and control as well as a preparation method and application of the composite cation corrosion inhibitor. The corrosion inhibitor is composed of cetyl pyridinium chloride, dodecyl trimethyl ammonium bromide, a nonionic surfactant and sodium molybdate. By optimizing the compounding ratio and adding the nonionic surfactant, the critical micelle concentration of the mixed system is reduced, the formation of micelles is remarkably inhibited, and the monomer adsorption efficiency is improved. The preparation process comprises gradient dissolution, passivation synergistic treatment and finished product forming, and uniform dispersion and synergistic effect of the components are ensured. Compared with a single cationic surfactant, the corrosion inhibitor has the advantages that an adsorption film is compact and stable, the corrosion inhibitor has passivation induction and physical barrier functions, particularly in a high-temperature (60-80 DEG C) acidic (pH 3-5) environment, the corrosion inhibition efficiency of the low-concentration composite corrosion inhibitor is superior to that of a high-concentration single surfactant, and meanwhile, the inhibition effect on microbial activity is remarkable; the method is suitable for high-corrosion risk scenes such as oil and gas pipelines and ocean platforms.

Description

Technical Field

[0001] The invention relates to the technical field of metal microbial corrosion protection, and in particular to a preparation method and application of a composite cationic corrosion inhibitor based on critical micelle concentration regulation. Background Art

[0002] In the petroleum, chemical, energy and other industries, metal equipment is often in a high-temperature acidic environment and is susceptible to corrosion, which can lead to reduced equipment performance, shortened service life, and even safety accidents. Although traditional corrosion inhibitors can alleviate corrosion problems to a certain extent, they are limited in effectiveness under extreme working conditions, and are often sensitive to the environment and easily affected by microorganisms and become ineffective.

[0003] The corrosion inhibition efficiency of traditional cationic surfactants (such as CPC and DTAB) is significantly reduced in high-temperature acidic environments due to electrostatic repulsion (positively charged metal surface) and molecular thermal desorption, and it is difficult for a single component to take into account the adsorption stability, passivation ability and microbial activity inhibition requirements; at the same time, micelles are easily formed when used in high concentrations, resulting in a decrease in effective adsorption and increased costs. In the existing technology, the comprehensive performance of corrosion inhibitors is insufficient for extreme working conditions such as high temperature (>60°C), acidity (pH<5) and the presence of microorganisms, and cannot meet the long-term protection needs of oil and gas fields, marine engineering and other scenarios. Summary of the invention

[0004] The purpose of the present invention is to provide a composite cationic corrosion inhibitor that can improve adsorption efficiency by regulating critical micelle concentration (CMC) and is resistant to high temperature and acidic environments, so as to solve the failure problem of traditional corrosion inhibitors under extreme conditions of high temperature (>60°C), acidity (pH<5) and containing microorganisms, and achieve efficient, long-term and economical corrosion protection.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions: A composite cationic corrosion inhibitor based on critical micelle concentration regulation, comprising the following components by mass percentage: Hexadecylpyridinium chloride 50-70%; Dodecyltrimethylammonium bromide 20-30%; Nonionic surfactant 5-10%; Sodium molybdate 3-5%.

[0006] Furthermore, the nonionic surfactant is Tween 80.

[0007] The preparation method of the composite cationic corrosion inhibitor comprises the following steps: (1) Gradient dissolution: stir and dissolve dodecyltrimethylammonium bromide, cetylpyridinium chloride, and Tween 80 in deionized water in sequence, control the temperature to ≤40°C, and stir at a speed of 300-500 rpm; (2) Passivation synergistic treatment: Add sodium molybdate, adjust the pH to alkaline, and ultrasonically disperse for 20 min; (3) Cool the solution obtained in step (3) to room temperature, filter, and dry to obtain the composite cationic corrosion inhibitor.

[0008] Further, the frequency of the ultrasonic dispersion in step (2) is 40 kHz.

[0009] The above-mentioned composite cationic corrosion inhibitor can be applied to oilfield drilling protection. The oilfield drilling is a corrosive medium environment with microbial corrosion, a temperature ≤ 80 °C, and a pH of 3 - 10.

[0010] A method for inhibiting metal corrosion is to add the above-mentioned composite cationic corrosion inhibitor to a corrosive medium containing microorganisms. The addition amount is less than the critical micelle concentration of the composite corrosion inhibitor, and the critical micelle concentration < 500 μM.

[0011] The corrosion inhibitor provided by the present invention has raw materials for preparing the corrosion inhibitor including a cationic surfactant, a non-ionic surfactant, and a passivation synergist. Among them, the cationic surfactant: cetylpyridinium chloride (CPC), forms a dense adsorption layer through π-π stacking and electrostatic adsorption, and induces the formation of a passivation film; dodecyltrimethylammonium bromide (DTAB), provides flexible adsorption compensation at high temperatures; the non-ionic surfactant: (preferably polyoxyethylene sorbitan monooleate Tween 80), inhibits micelle formation and enhances adsorption uniformity; the passivation synergist sodium molybdate, strengthens the compactness of the passivation film and improves the Cl - penetration ability.

[0012] The corrosion inhibitor provided by the present invention is compounded and optimized under the regulation of the critical micelle concentration (CMC). CPC and DTAB are compounded according to a mass ratio, and the CMC of the mixed system decreases. After adding Tween 80, the CMC of the mixed solution further decreases, ensuring that the surfactant is preferentially adsorbed in the monomer form.

[0013] Further, using the composite cationic corrosion inhibitor provided by the present invention and adding it to a corrosive medium containing microorganisms, the addition amount is less than the critical micelle concentration of the corrosion inhibitor. Within the CMC range, the corrosion inhibitor molecules can spontaneously form micelles, improving the adsorption efficiency and corrosion inhibition performance on the metal surface.

[0014] The beneficial effects of the present invention are as follows: (1) The corrosion inhibitor provided by the present invention, compared with the single use of CPC or DTAB, realizes a multiple synergistic mechanism of adsorption - passivation - sterilization through component synergy: the pyridine ring of CPC preferentially adsorbs on the metal active sites through π-π stacking and induces a passivation film, but the defect of its easy desorption at high temperature is dynamically filled by the flexible dodecyl chain of DTAB to form a continuous adsorption layer. At the same time, the weak electrostatic repulsion of DTAB in the acidic environment can partially make up for the adsorption failure of CPC caused by the positive charge on the metal surface; while the passivation ability of CPC compensates for the shortcoming of DTAB lacking chemical protection. After compounding, Tween 80 further reduces the CMC of the mixed solution by inhibiting micellization and improves the effective adsorption amount, and sodium molybdate strengthens the compactness of the passivation film.

[0015] (2) The corrosion inhibitor provided by the present invention has an improved corrosion inhibition efficiency at a lower concentration in a high-temperature acidic environment (67°C, pH = 3) compared with a higher concentration of a single surfactant (CPC and DTAB). At the same time, it combines the advantages of CPC directly killing microorganisms and DTAB inhibiting biofilm adhesion, inhibits the microbial activity, and reduces the pitting density. This system solves the problems of unstable adsorption, passivation failure and microbial corrosion of single components under extreme working conditions through a dynamic adsorption repair and passivation-barrier dual-effect mechanism, and is more environmentally friendly and lower in cost.

[0016] (3) Based on the CMC regulation strategy, the present invention significantly reduces the CMC of the mixed system through compounding and synergism with non-ionic surfactants, breaks through the micellization limit, and improves the monomer adsorption efficiency. Passivation-adsorption dual-effect mechanism: CPC induces a passivation film, DTAB provides dynamic adsorption compensation, and sodium molybdate strengthens the film compactness to achieve synergistic protection under extreme working conditions. For the first time, the adsorption behavior of cationic surfactant compounding is optimized through CMC regulation, breaking through the corrosion inhibition bottleneck in a high-temperature acidic environment. It is applicable to high-corrosion-risk scenarios such as oil and gas fields and offshore platforms, with a simple process and controllable costs. It is highly efficient at low concentrations and its biodegradability meets the ISO 14593 standard.

[0017] (4) Process adaptability: The gradient dissolution and ultrasonic dispersion process ensures uniform dispersion of components and takes into account the feasibility of industrial production. Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the surface tension of two surfactants changing with concentration.

[0019] Figure 2 It is a schematic diagram of the surface tension of the composite corrosion inhibitor changing with concentration.

[0020] Figure 3 It is an electrochemical test device. Detailed Embodiments

[0021] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0022] The present invention relates to a preparation method and application of a composite cationic corrosion inhibitor, and the specific embodiments are as follows: Example 1 Preparation of Corrosion Inhibitor and Test Medium The corrosion inhibitor, calculated by mass percentage, contains 60% CPC, 25% DTAB, 10% Tween 80, and 5% sodium molybdate. The specific preparation steps are as follows: (1) Add DTAB to deionized water at 40 °C, stir at 400 rpm for 10 min until completely dissolved, then add CPC, maintain the temperature ≤ 40 °C, and continue stirring for 10 min.

[0023] (2) Add Tween 80 to the solution obtained in step (1), stir for 10 min, and adjust the pH to 8.5 with sodium hydroxide to form a homogeneous and transparent solution.

[0024] (3) Add sodium molybdate to the solution obtained in step (2), transfer the mixture to an ultrasonic reactor (40 kHz), and perform dispersion treatment for 20 min to eliminate bubbles and enhance molecular synergy.

[0025] (4) After the ultrasonic treatment, cool the solution to room temperature, filter to remove unreacted raw materials and impurities to obtain a pure composite corrosion inhibitor solution, filter the solution by suction and dry it into powder to prepare the finished product for easy storage.

[0026] The schematic diagram of the surface tension of the two surfactants changing with concentration is shown in Figure 1 The surface tension of the composite corrosion inhibitor changing with concentration is shown in Figure 2 .

[0027] Example 2 Construction and Testing of the Experimental Platform First, add the solid powder of the composite corrosion inhibitor to the simulated oilfield acidic produced water solution, then add the enriched culture solution of sulfate-reducing bacteria (SRB), and place it in a constant temperature incubator at 37°C for cultivation. The addition amount of the SRB enriched culture solution was strictly controlled to ensure that its volume ratio reached 2% of the total volume of the simulated oilfield produced water solution. The introduction of this step aims to simulate the corrosion effect of SRB on metal materials in the actual environment and evaluate the protection effect of the corrosion inhibitor in the presence of SRB. The pH of the simulated oilfield acidic produced water solution is 3, the Cl⁻ concentration is 15000 ppm, and the temperature is 67°C [See the literature Wang J, Du M, Shan X. Effect of marine Streptomyces on corrosion behavior of X65 steel in simulated offshore oilfield produced water system[J]. Journal of Materials Research and Technology, 2023, 24(000):13.].

[0028] For the corrosion inhibitor provided by the present invention, the methods for evaluating its corrosion inhibition effect include electrochemical tests, weight loss experiments, and microbial counting.

[0029] In the corrosion electrochemistry experiment, by measuring the open circuit potential of the metal electrode and the polarization curve obtained by potentiodynamic scanning, and combining with the electrochemical analysis software to fit the strong polarization region of the polarization curve by the Tafel extrapolation method, key electrochemical parameters such as corrosion current density and polarization resistance are further extracted. Specifically, a three-electrode system is adopted, and in the set high-temperature acidic environment, the polarization curves and alternating current impedance spectra of the metal material before and after adding the corrosion inhibitor are measured. By comparing parameters such as corrosion potential and corrosion current density in the polarization curve, and parameters such as electrochemical reaction resistance in the alternating current impedance spectrum, the corrosion inhibition efficiency of the corrosion inhibitor is evaluated.

[0030] Specifically, in the same high-temperature acidic environment, the metal material is immersed in solutions with and without the corrosion inhibitor, taken out and cleaned after a certain time. By measuring the mass change of the metal material before and after the experiment, the corrosion rate is calculated to quantify the corrosion inhibition effect of the corrosion inhibitor.

[0031] Specifically, an appropriate amount of the corrosion inhibitor is added to the culture medium containing microorganisms, and the growth of microorganisms is observed. The number of microorganisms in the planktonic solution and on the fixed metal surface is counted by the extinction dilution method to evaluate the inhibitory effect of the corrosion inhibitor on the growth of microorganisms and verify its applicability in the microorganism-containing environment.

[0032] Figure 3It is an electrochemical measurement device. In the measurement, the test device uses a three - electrode system with an X80 pipeline steel specimen as the working electrode. At the same time, a platinum electrode is used as the counter electrode and a saturated calomel electrode is used as the reference electrode in the test system. This device is used for measuring the strong polarization curve of the specimen.

[0033] Application Comparative Example 1 Add 500 μM of DTAB and CPC to the simulated oilfield acidic produced water solution as corrosion inhibitors respectively. Tables 1 - 4 show the polarization curve fitting results and weight loss results of X80 steel at different pH values of 67°C. The control is without adding any corrosion inhibitor.

[0034] Table 1 Corrosion kinetic parameters of X80 steel after 14 days at different pH values of 67°C with 500 μM of DTAB added Table 2 Corrosion kinetic parameters of X80 steel after 14 days at different pH values of 67°C with 500 μM of CPC added Table 3 Weight loss and corrosion inhibition efficiency of X80 steel after 14 days at different pH values of 67°C with 500 μM of DTAB added Table 4 Weight loss and corrosion inhibition efficiency of X80 steel after 14 days at different pH values of 67°C with 500 μM of CPC added Application Example 1 Add 100 μM of the composite corrosion inhibitor prepared in Example 1 to the simulated oilfield acidic produced water solution. The results are shown in Table 5.

[0035] Table 5 Polarization and weight loss results of the compound corrosion inhibitor with 100 μM added after 14 days at 67°C and pH = 3 Table 6 Number of planktonic and sessile SRB after 14 days of DTAB immersion in the test medium Table 7 Number of planktonic and sessile SRB after 14 days of CPC immersion in the test medium Table 8 Number of planktonic and sessile SRB after 14 days of the composite corrosion inhibitor immersion in the test medium The results show that when CPC and DTAB are respectively added as corrosion inhibitors, the corrosion inhibition efficiency is greatly reduced in a high-temperature acidic environment, and CPC, which shows a better corrosion inhibition effect, has a poor corrosion inhibition effect under such environmental conditions. However, adding a lower concentration of the compound corrosion inhibitor effectively improves the corrosion inhibition efficiency in an acidic high-temperature environment. The advantage of the compound corrosion inhibitor stems from the synergistic complementary mechanism between CPC and DTAB: the rigid pyridine ring of CPC is preferentially adsorbed on the metal active sites through π-π stacking and induces the formation of a passive film), but the defect of its easy desorption at high temperature is dynamically filled by the flexible dodecyl chain of DTAB to form a continuous adsorption layer; at the same time, the electrostatic repulsion of DTAB in an acidic environment is weak, which can partially compensate for the adsorption failure caused by the positive charge on the surface of CPC, while the passivation ability of CPC makes up for the shortcoming of DTAB lacking chemical protection. After the two are compounded, the advantages of directly destroying the SRB cell membrane by CPC and inhibiting the adhesion of biofilms by DTAB are combined, and Tween 80 is used to inhibit micellization and sodium molybdate to strengthen the passive film, finally achieving triple synergy of adsorption-passivation-bactericidal in a high-temperature acidic environment, and the corrosion inhibition efficiency is improved compared with single components.

[0036] Enlightened by the ideal embodiments of the present invention described above, through the above description, relevant workers can make various changes and modifications without departing from the scope of the present invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A composite cationic corrosion inhibitor based on critical micelle concentration regulation, characterized in that: Calculated by mass percentage, it contains the following components: Hexadecylpyridinium chloride 50-70%; Dodecyltrimethylammonium bromide 20-30%; Nonionic surfactant 5-10%; Sodium molybdate 3-5%.

2. The composite cationic corrosion inhibitor according to claim 1, characterized in that: The nonionic surfactant is Tween 80.

3. A method for preparing a composite cationic corrosion inhibitor as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Gradient dissolution: Dissolve dodecyltrimethylammonium bromide, hexadecylpyridinium chloride, and Tween 80 in deionized water in sequence by stirring, control the temperature to ≤40°C, and stir at a speed of 300-500 rpm; (2) Passivation synergistic treatment: add sodium molybdate, adjust the pH to alkaline, and ultrasonically disperse for 20 min; (3) The solution obtained in step (3) is cooled to room temperature, filtered, and dried to obtain a composite cationic corrosion inhibitor.

4. The preparation method according to claim 3, characterized in that: The frequency of the ultrasonic dispersion in step (2) is 40 kHz.

5. Use of the composite cationic corrosion inhibitor as claimed in claim 1 in oil field drilling protection.

6. The use according to claim 5, characterized in that: Oilfield drilling is a corrosive medium environment with microbial corrosion, temperature ≤80℃, and pH 3-10.

7. A method for inhibiting metal corrosion, characterized in that: The composite cationic corrosion inhibitor according to claim 1 is added to a corrosive medium containing microorganisms, and the added amount is less than the critical micelle concentration of the composite corrosion inhibitor, and the critical micelle concentration is less than 500 μM.

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