Green multifunctional corrosion inhibition method and its corrosion inhibitor composition

Abstract

The present application belongs to the technical field of industrial water treatment and metal corrosion prevention, and relates to a green multifunctional corrosion inhibition method and a corrosion inhibitor composition thereof. The corrosion inhibition method comprises the following steps: dissolving a water-soluble borate in a fluid medium containing a metal pipeline to be protected, fully stirring, and forming a weak alkaline buffer solution containing a "boric acid-borate" conjugate acid-base pair through a hydrolysis reaction; adding a mussel-biomimetic catechol compound and an amine-based compound to the weak alkaline buffer solution, and sealing and stirring at normal temperature and pressure; and using the oxidation self-polymerization of the mussel-biomimetic catechol compound and the reaction of the mussel-biomimetic catechol compound with the amine-based compound to form a high-efficiency composite protective film with strong adhesion on the metal surface. The corrosion inhibition system constructed in situ by the method has excellent corrosion inhibition efficiency, pH buffering and oxygen capture performance, and the metal corrosion inhibition effect is better than that of a simple physical mixed compound. The method is simple and easy to implement, has mild reaction conditions, is low in cost, and is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of industrial water treatment and metal corrosion prevention technology, specifically relating to a green multifunctional corrosion inhibition method and its corrosion inhibitor composition. Background Technology

[0002] Metal corrosion is a critical issue restricting the safe, environmentally friendly, long-term stable operation, and asset integrity management of equipment and facilities in the petroleum, petrochemical, and water treatment industries. Adding corrosion inhibitors is the most common and cost-effective method for controlling corrosion in systems such as pipelines, storage tanks, or industrial equipment. Their mechanism of action involves forming a dense barrier layer (including oxide film, precipitation film, and adsorption film types) on the metal surface, preventing corrosive substances (water, oxygen, carbon dioxide, hydrogen sulfide, or chlorides) from contacting the metal, or altering the electrochemical reactions driving corrosion, thus inhibiting the anodic and cathodic reaction rates. High-efficiency corrosion inhibitors are key materials for ensuring pipeline safety and improving the overall life-cycle benefits of water treatment pipeline installations.

[0003] Currently, commonly used corrosion inhibition methods employ corrosion inhibitors, primarily inorganic and organic. Inorganic corrosion inhibitors often contain highly electronegative atoms such as nitrogen, oxygen, sulfur, and phosphorus, including arsenates, phosphates, and chromates. Organic corrosion inhibitors are mainly organic heterocyclic compounds containing unsaturated bonds or large conjugated systems, such as imidazoles, Schiff bases, and pyridines. Among these, imidazole-based corrosion inhibitors are the most widely used in the oil and gas industry. In practical applications, corrosion inhibitors often exhibit antagonistic effects when mixed with deoxidizers, bactericides, scale inhibitors, and pH adjusters, leading to the failure of their corrosion inhibition performance and increasing the maintenance costs of metal pipeline facilities. Furthermore, the complex structures, difficult preparation, high prices, high ecotoxicity, and non-biodegradability of these corrosion inhibitors limit their precise corrosion prevention applications and sustainable development in the petrochemical and water treatment industries.

[0004] Based on the concepts of ecological environmental protection and green sustainable development, it is urgent to develop a multifunctional green corrosion inhibition method that can adapt to complex water quality changes, is efficient, and is easy to operate. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a green, multifunctional corrosion inhibition method and its corrosion inhibitor composition. This method constructs an in-situ corrosion inhibition system that combines pH buffering, oxygen capture, and metal corrosion inhibition. The operation is simple and easy, the reaction conditions are mild and the process is controllable, and it exhibits excellent corrosion protection performance for bare steel, rusted steel, and other metal pipelines.

[0006] The technical solution of this invention is: The first aspect of this invention provides a green, multifunctional corrosion inhibition method, comprising the following steps: (1) Dissolve water-soluble boron salt in a fluid medium containing the metal surface to be protected, stir evenly, and form a weakly alkaline buffer solution containing the conjugate acid-base pair of "boric acid-tetrahydroxyborate ion" through hydrolysis reaction; (2) Mussel biomimetic catechol compounds and amine compounds are added to the weakly alkaline buffer solution and stirred under sealed conditions at room temperature and pressure. The mussel biomimetic catechol compounds undergo oxidative self-polymerization and react with the amine compounds in a Schiff base reaction or a Michael addition reaction to form a composite protective film on the metal surface.

[0007] Preferably, the water-soluble boron salt is one or more of sodium tetraborate, potassium tetraborate, sodium metaborate, and potassium metaborate, and the amount of water-soluble boron salt added is such that the boron concentration in the fluid medium is 0.5-200 mg / L and the solution pH is 7.88-8.84.

[0008] Preferably, the stirring time in step (1) is 0.5-2 hours.

[0009] Preferably, the mussel-inspired catechol compound is one or more of dopamine, tannic acid, gallic acid, catechol, 3,4-dihydroxy-L-phenylalanine, 3,4,5-trihydroxyphenylalanine, polydopamine, and dopamine-acrylic acid copolymer.

[0010] Preferably, the amine compound is one or more of piperazine, m-phenylenediamine, polyethyleneimine, polylysine, triethylenetetramine, and tetraethylenepentamine.

[0011] Preferably, the mass ratio of the mussel-inspired catechins to the amines is 1:4 to 8:1, and the concentration of the catechins and amines in the weakly alkaline buffer solution is 10-60 mg / L.

[0012] Preferably, the fluid medium includes one or more of nanofiltration seawater, reverse osmosis desalinated water, municipal wastewater, oilfield produced water, industrial circulating cooling water, brackish water, and concentrated brine from seawater desalination.

[0013] Preferably, step (1) involves stirring for 0.5-2 hours, and step (2) involves sealing and stirring for 10-60 minutes.

[0014] Preferably, the metal surface to be protected is one or more of carbon steel, low-alloy steel, stainless steel, copper alloy, and aluminum alloy. The metal surface to be protected can be a pipe in an oilfield water injection system, an industrial water treatment pipe, etc.

[0015] A second aspect of the present invention provides a corrosion inhibitor composition for the above-mentioned corrosion inhibition method, the corrosion inhibitor composition comprising a water-soluble boron salt, a mussel biomimetic catechol compound, and an amino compound, the three being independent components before use. During use, the water-soluble boron salt is added to the fluid medium first, followed by the mussel biomimetic catechol compound and the amino compound.

[0016] Preferably, the mass ratio of the mussel-inspired catechol compounds to the amine compounds is 1:4 to 8:1, the boron concentration in the fluid medium is 0.5-200 mg / L, and the concentrations of the catechol compounds and amine compounds in the weakly alkaline buffer solution are 10-60 mg / L.

[0017] This invention employs a "step-by-step addition and in-situ compounding" corrosion inhibition method. First, water-soluble boron salts are directly dissolved in the fluid medium of the metal pipeline to form a weakly alkaline buffer system containing a conjugate acid-base pair of "boric acid-tetrahydroxyborate ion". Then, mussel-inspired catechol compounds and amine compounds are added to the system to obtain a green multifunctional corrosion inhibition system with pH buffering, oxygen capture, antibacterial, and metal corrosion inhibition functions. When this corrosion inhibition system is used for metal pipeline corrosion protection, the initially constructed weakly alkaline buffer system provides a stable weakly alkaline environment. The multiple ortho-phenolic hydroxyl groups contained in the mussel-inspired catechol compounds (such as catechol) have a strong chelating and adsorption capacity for the metal surface of the pipeline. At the same time, dissolved oxygen is captured under weakly alkaline conditions, and an adhesion layer is formed on the metal surface through an oxidative self-polymerization reaction. Meanwhile, the amine compounds further undergo Schiff base or Michael addition reactions with the oxidation products of the catechol compounds, synergistically enhancing the interaction of the adhesion layer interface and generating a composite protective film with durable adhesion and anti-corrosion properties in situ on the metal surface. The organic combination of the initially constructed pH buffer system protective layer and the highly efficient synergistic film formation of catechol and amine compounds improves the corrosion inhibition efficiency of metals.

[0018] The advantages and beneficial effects of this invention are: (1) The corrosion inhibition system constructed in situ by the method of the present invention has excellent corrosion inhibition efficiency, pH buffering and oxygen capture performance, and the metal corrosion inhibition effect is better than that of simple physical mixing compound agents. When testing exposed Q235 carbon steel in nanofiltration seawater, the corrosion inhibition rate can reach 60.9%, the dissolved oxygen content drops to 0.3-0.4 mg / L, and the pH is stable.

[0019] (2) The green and multifunctional corrosion inhibition method of this invention is simple and easy to implement, with mild reaction conditions and controllable process. It does not require complex synthesis processes and can be directly added to the flowing medium in steps. The addition ratio of each component can be flexibly adjusted according to the water quality, resulting in high cost-effectiveness. Moreover, this method is not sensitive to water quality fluctuations such as salinity and pH changes, and can adapt to complex water environment systems. It can effectively solve the corrosion problem of pipelines and equipment caused by highly corrosive oilfield water injection with lower dosage, and has good application scenarios in the fields of offshore oilfield nanofiltration, reverse osmosis water injection systems, and industrial circulating water networks.

[0020] (3) The corrosion inhibitor composition of the present invention has a simple formulation, reduces the types of agents to be added, and has low cost. The core functional material - catechin compounds - is derived from marine mussel biomimetic materials and contains only carbon, nitrogen and oxygen basic elements, which is environmentally friendly. Attached Figure Description

[0021] Figure 1 The Nquist spectrum of AC impedance in Example 1; Figure 2 The polarization curve Tafel spectrum of Example 1; Figure 3 The image shows a scanning electron microscope image of Q235 carbon steel from Example 1 after being suspended in nanofiltration seawater containing a corrosion inhibitor composition for 7 days. Figure 4 The image shows a scanning electron microscope image of Q235 carbon steel from Comparative Example 1 after being coated in nanofiltration seawater without the addition of corrosion inhibitor composition for 7 days. Figure 5 The image shows a scanning electron microscope image of Q235 carbon steel from Comparative Example 1 after being suspended in nanofiltration seawater containing commercial imidazoline corrosion inhibitors for 7 days. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. However, the inventive concept of the present invention is not limited to the specific steps of the embodiments. Those skilled in the art can make equivalent changes based on the prior art prior to the application date of the present invention.

[0023] Example 1 In a 200 mL three-electrode glass electrolytic cell, 200 mL of nanofiltration seawater (ionic composition shown in Table 1) was added. First, sodium tetraborate was added and stirred thoroughly for 30 minutes. Hydrolysis resulted in a weakly alkaline buffer solution containing a conjugate acid-base pair of borate-tetrahydroxyborate ions. The boron concentration in the buffer solution was 40 mg / L, and the pH was 8.31. Subsequently, dopamine and polyethyleneimine were added to the buffer solution at a mass ratio of 2:1, with dopamine concentration of 20 mg / L and polyethyleneimine concentration of 10 mg / L. The mixture was then sealed and stirred for 30 minutes at room temperature and pressure to construct an in-situ corrosion inhibition system.

[0024] Then, a saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Q235 carbon steel was used as the working electrode (simulating the metal to be protected). AC impedance testing was performed at steady-state open-circuit potential (OCP) with a frequency range of 10 Hz. 5 The frequency band was Hz to 0.1 Hz, with an amplitude of 0.01 V and an AC disturbance voltage amplitude of 5 mV. Ten data points were collected every ten octaves, using a logarithmic frequency distribution scan. The Tafel polarization curve method was implemented at steady-state open-circuit potential (OCP), with the test starting at OCP -250 mV and ending at OCP +250 mV, at a scan rate of 0.1667 mV / s. Based on these parameters, AC impedance and polarization curve tests were performed, and the surface charge transfer resistance (R) of carbon steel was measured. ct The Ω was 785.2, the corrosion rate was 0.0265 mm / a, and the corrosion inhibition rate reached 60.9%. The dissolved oxygen content decreased from 5.4 mg / L to 0.3 mg / L, as measured by a dissolved oxygen meter (SH-820, Jiangsu Shengaohua), and the pH was stable at 8.30±0.2, as measured by a pH meter (PHS-3E, Shanghai Leici). Figure 1 The Nquist spectrum is plotted with the real part of impedance on the x-axis and the imaginary part on the y-axis. The red scatter points represent experimental data, and the dashed line represents the fitting curve based on the equivalent circuit. The high overlap between the two indicates a good fitting effect. The capacitive arc diameter corresponds to the charge transfer resistance R. ct The resistance is 758.2 Ω, which reflects the large resistance to interfacial charge transfer and the slow corrosion reaction rate. Figure 2 The Tafel spectrum analysis shows that both the anode and cathode branches of the sample exhibit a clear Tafel linear region, indicating that the corrosion process is activation-controlled and the charge transfer step is the corrosion rate-controlling step. The ordinate corresponding to the intersection of the anodic and cathodic polarization curves represents the self-corrosion potential, which is -0.67207 V. The corrosion current density obtained by extrapolating and fitting the Tafel curve is 0.050 μA·cm. -2 Less than 1 μA·cm -2 The low corrosion current density indicates that the sample exhibits excellent corrosion resistance in the test environment.

[0025] Seven days after the coating was applied, a uniform protective layer was observed on the carbon steel surface using a scanning electron microscope. No accumulation of corrosion products was observed (e.g., ...). Figure 3 (As shown).

[0026] Table 1. Main ionic composition (mg / L) of nanofiltered seawater and raw seawater.

[0027] Example 2 In a 200 mL three-electrode glass electrolytic cell, 200 mL of nanofiltration seawater (ionic composition shown in Table 1) was added. Sodium metaborate was added first, and the mixture was stirred thoroughly for 30 minutes. Following hydrolysis, a weakly alkaline buffer solution containing a conjugate acid-base pair of borate-tetrahydroxyborate ions was formed. The boron concentration in the buffer solution was 40 mg / L, and the pH was 8.31. Subsequently, gallic acid and polyethyleneimine were added to the buffer solution at a mass ratio of 2:1, with gallic acid concentration of 20 mg / L and polyethyleneimine concentration of 10 mg / L. The mixture was then sealed and stirred for 30 minutes at room temperature and pressure to construct an in-situ corrosion inhibition system.

[0028] Then, using a saturated calomel electrode as the reference electrode and a platinum sheet as the auxiliary electrode, with an exposed area of ​​2.104 cm², 2 Using Q235 carbon steel as the working electrode (simulating the metal to be protected), AC impedance and polarization curve tests were performed, with the same test parameters as in Example 1. The charge transfer resistance (R) on the carbon steel surface was measured. ct The Ω value was 654.6, the corrosion rate was 0.0307 mm / a, the corrosion inhibition rate reached 54.9%, the dissolved oxygen content decreased from 5.5 mg / L to 0.4 mg / L, and the pH stabilized at 8.20 ± 0.2. After 7 days of application, a uniform protective layer was observed on the carbon steel surface using scanning electron microscopy, and no enrichment of corrosion products was observed.

[0029] Comparative Example 1 The difference from Example 1 is that no corrosion inhibitor was added. Instead, 200 mL of nanofiltered seawater (ionic composition shown in Table 1) was directly placed in a 200 mL three-electrode glass electrolytic cell, using a saturated calomel electrode as the reference electrode and a platinum sheet as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Using Q235 carbon steel as the working electrode, AC impedance and polarization curve tests were performed, with the same test parameters as in Example 1. The surface charge transfer resistance (R) of the carbon steel was measured. ct The Ω value was 295.2, the corrosion rate was 0.0680 mm / a, the dissolved oxygen content decreased from 5.4 mg / L to 1.5 mg / L, and the solution pH value decreased from 7.90 to 7.65. Seven days after application, scanning electron microscopy revealed that the carbon steel surface was covered with corrosion products (such as...). Figure 4 ).

[0030] Comparative Example 2 The difference from Example 1 is that 40 mg / L of commonly used oilfield imidazoline corrosion inhibitor (Shenyang Zhongke Mingyang Corrosion and Protection Co., Ltd., MY-30Q corrosion inhibitor) was added to 200 mL of nanofiltration seawater (ionic composition shown in Table 1). The mixture was sealed in a three-electrode glass electrolytic cell and stirred at 25°C for 1 hour. A saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Using Q235 carbon steel as the working electrode, AC impedance and polarization curve tests were performed, with the same test parameters as in Example 1. The surface charge transfer resistance (R) of the carbon steel was measured. ct The Ω value was 466.4, the corrosion rate was 0.0432 mm / a, the corrosion inhibition rate reached 31.8%, the dissolved oxygen content decreased from 5.4 mg / L to 1.6 mg / L, and the solution pH value decreased from 7.85 to 7.58. Seven days after the plates were applied, local pitting corrosion was observed on the carbon steel surface using a scanning electron microscope (e.g., ...). Figure 5 ).

[0031] Comparative Example 3 The difference from Example 1 is that 200 mL of nanofiltered seawater (ionic composition shown in Table 1) was taken, and the same amounts of sodium tetraborate, dopamine, and polyethyleneimine as in Example 1 were added simultaneously. The mixture was then sealed and stirred for 30 minutes to obtain a corrosion inhibitor. In a three-electrode glass electrolytic cell, a saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Using Q235 carbon steel as the working electrode, with the addition of a corrosion inhibitor, AC impedance and polarization curve tests were performed, and the surface charge transfer resistance (R) of the carbon steel was measured. ct The Ω value was 509.1, the corrosion rate was 0.0396 mm / a, and the corrosion inhibition rate was 41.7%. Furthermore, the simultaneous addition of the reagents caused a large amount of black flocculent precipitate to instantly form in the solution, increasing the risk of pipeline blockage. This demonstrates that the specific order of "first constructing a borate-tetrahydroxyborate ion buffer layer, then adding catechol / amine for reaction" is crucial for forming an efficient and dense protective film, rather than a simple physical mixing.

[0032] Comparative Example 4 In 200 mL of nanofiltration seawater (ionic composition shown in Table 1), sodium tetraborate was first added and stirred thoroughly for 30 minutes. After hydrolysis, a weakly alkaline buffer solution containing the conjugate acid-base pair of "boric acid-tetrahydroxyborate ion" was formed. The boron concentration in the weakly alkaline buffer solution was 40 mg / L, and the pH was 8.31.

[0033] Subsequently, hydroquinone and polyethyleneimine were added to a weakly alkaline buffer solution at a mass ratio of 2:1, with a total concentration of 30 mg / L. The mixture was then stirred under sealed conditions at room temperature and pressure for 30 minutes to obtain the corrosion inhibitor.

[0034] In a three-electrode glass electrolytic cell, a saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Using Q235 carbon steel as the working electrode, the aforementioned corrosion inhibitor was added, and AC impedance and polarization curve tests were performed. The surface charge transfer resistance (R) of the carbon steel was measured. ct The Ω value was 482.8, the corrosion rate was 0.0417 mm / a, the corrosion inhibition rate reached 38.7%, and the dissolved oxygen content decreased from 5.4 mg / L to 0.3 mg / L. Furthermore, a large number of fragmented precipitates appeared in the solution, proving that the specific "catechol structure" (catechol group) is the core of achieving strong adhesion; other compounds with similar structures but lacking this feature cannot achieve the same effect.

[0035] Comparative Example 5 In 200 mL of nanofiltration softened water, the pH of the solution was adjusted to 8.31 using NaOH to obtain a buffer solution. Subsequently, dopamine and polyethyleneimine were added to the weakly alkaline buffer solution at a mass ratio of 2:1, with a total concentration of 30 mg / L. The solution was then sealed and stirred for 30 minutes at room temperature and pressure to obtain a corrosion inhibitor.

[0036] In a three-electrode glass electrolytic cell, a saturated calomel electrode was used as the reference electrode, and a platinum sheet was used as the auxiliary electrode, with an exposed area of ​​2.104 cm². 2 Using Q235 carbon steel as the working electrode, the aforementioned corrosion inhibitor was added, and AC impedance and polarization curve tests were performed. The surface charge transfer resistance (R) of the carbon steel was measured. ct The Ω value was 476.9, the corrosion rate was 0.0423 mm / a, the solution pH decreased from 8.31 to 7.97, the corrosion inhibition rate reached 37.8%, and the dissolved oxygen content decreased from 5.4 mg / L to 0.4 mg / L. Furthermore, a large amount of black particulate precipitate appeared in the solution. This indicates that the "boric acid-tetrahydroxyborate ion" buffer system constructed in Example 1 of this invention not only provides an alkaline environment, but the conjugate acid-base pair formed by it also makes a unique contribution to the stability of the system, which is superior to simple pH adjustment.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A green, multifunctional corrosion inhibition method, characterized in that, Includes the following steps: (1) Dissolve water-soluble boron salt in a fluid medium containing the metal surface to be protected, stir evenly, and form a weakly alkaline buffer solution containing the conjugate acid-base pair of "boronic acid-tetrahydroxyborate ion" through hydrolysis reaction; (2) Mussel biomimetic catechol compounds and amine compounds are added to the weakly alkaline buffer solution and stirred under sealed conditions at room temperature and pressure. The mussel biomimetic catechol compounds undergo oxidative self-polymerization and react with the amine compounds via Schiff base reaction or Michael addition reaction to form a composite protective film on the metal surface. The mussel biomimetic catechol compounds are one or more of dopamine, tannic acid, gallic acid, catechol, 3,4-dihydroxy-L-phenylalanine, 3,4,5-trihydroxyphenylalanine, polydopamine, and dopamine-acrylic acid copolymer. The amine compounds are one or more of piperazine, m-phenylenediamine, polyethyleneimine, polylysine, triethylenetetramine, and tetraethylenepentamine.

2. The method according to claim 1, characterized in that, The water-soluble boron salt is one or more of sodium tetraborate, potassium tetraborate, sodium metaborate, and potassium metaborate. The amount of water-soluble boron salt added is such that the boron concentration in the fluid medium is 0.5-200 mg / L and the solution pH is 7.88-8.

84.

3. The method according to claim 1, characterized in that, The mass ratio of the mussel-inspired catechol compounds to the amino compounds is 1:4 to 8:1, and the concentrations of the catechol compounds and amino compounds in the weakly alkaline buffer solution are 10-60 mg / L.

4. The method according to claim 1, characterized in that, The fluid medium includes one or more of nanofiltration seawater, reverse osmosis desalination water, municipal wastewater, oilfield produced water, industrial circulating cooling water, brackish water, and concentrated brine from seawater desalination.

5. The method according to claim 1, characterized in that, Step (1) Stir for 0.5-2 hours, Step (2) Seal and stir for 10-60 minutes.

6. The method according to claim 1, characterized in that, The metal surface to be protected is one or more of carbon steel, low alloy steel, stainless steel, copper alloy, and aluminum alloy.

7. A corrosion inhibitor composition for use in the corrosion inhibition method according to any one of claims 1-6, characterized in that, The corrosion inhibitor composition includes a water-soluble boron salt, a mussel-inspired catechol compound, and an amine compound. These three components are independent before use. During use, the water-soluble boron salt is added to the fluid medium first, followed by the mussel-inspired catechol compound and the amine compound.

8. The corrosion inhibitor composition according to claim 7, characterized in that, The mass ratio of the mussel-inspired catechol compounds to the amine compounds is 1:4 to 8:1, the boron concentration in the fluid medium is 0.5-200 mg / L, and the concentrations of the catechol compounds and amine compounds in the weakly alkaline buffer solution are 10-60 mg / L.

Images