Green environment-friendly gas-phase corrosion inhibitor and preparation method thereof

Abstract

This invention relates to the field of vapor phase corrosion inhibitors and discloses a green and environmentally friendly vapor phase corrosion inhibitor and its preparation method, which is composed of the following raw materials in the indicated mass percentages: phytic acid 30%-38%, citric acid 8%-12%, diethanolamine 32%-40%, morpholine 4%-8%, water 10%-15%, ethanol 4%-6%, benzotriazole 1.5%-2.5%, and alanine ternary complex 0.5%-3.0%. Phytic acid, extracted from rice bran processing byproducts, and citric acid, derived from citrus fruits, are used as the core organic acid components. The polyphosphate groups of these two components form a synergistic chelate system with the carboxyl groups. Combined with other green components, this eliminates dependence on non-renewable petrochemical products from the source of raw materials, truly realizing the green properties of the corrosion inhibitor, and exhibiting excellent biocompatibility. The alanine ternary complex, through the multi-coordination site structure formed by L-alanine, phosphoric acid, and dibutylamine, synergistically works with the heterocyclic structure of benzotriazole to fill the defects in the protective film formed by the adsorption of single benzotriazole, enhancing its adsorption and compatibility with different metal surfaces.

Description

Technical Field

[0001] This invention relates to the field of vapor phase corrosion inhibitor technology, specifically to a green and environmentally friendly vapor phase corrosion inhibitor and its preparation method. Background Technology

[0002] Metal materials and their products are highly susceptible to corrosion during storage, transportation, and use due to environmental humidity, oxygen, and corrosive atmospheres (such as Cl2, SO2, H2S, etc.). This corrosion leads to decreased equipment precision, performance impairment, and shortened lifespan, resulting in significant economic losses and resource waste. To prevent this atmospheric corrosion, vapor phase corrosion inhibitor (VCI) technology is widely used due to its high efficiency and convenience. VCI can automatically volatilize at room temperature and adsorb onto the metal surface to form a protective film, thereby isolating corrosive media and achieving long-term protection of metals in enclosed or semi-enclosed spaces.

[0003] Currently, traditional vapor phase corrosion inhibitors are mainly classified into the following categories: First, nitrites, such as dicyclohexylamine nitrite and sodium nitrite, which have excellent rust-preventing effects on ferrous metals; however, nitrites themselves are recognized carcinogens and pose a great threat to the environment and human health. With increasingly stringent global environmental regulations, their use is being gradually restricted and phased out. Second, inorganic salts such as chromates, molybdates, and phosphates, some of which have heavy metal pollution problems and do not conform to the development trend of green chemistry. Third, some compound compounds of organic amines and carboxylates, but many of these still rely on artificially synthesized chemicals, have poor biodegradability, or generate "three wastes" during the production process, and are not environmentally friendly enough.

[0004] In recent years, to address the aforementioned challenges, the scientific community has developed some so-called "environmentally friendly" corrosion inhibitors; for example, some technologies use benzotriazole and its derivatives as corrosion inhibitors for copper and its alloys, or attempt to use some low-toxicity organic acids; however, these solutions still have limitations: First, the active ingredients of many corrosion inhibitors still originate from non-renewable petrochemical products, failing to fundamentally achieve "green" status. Second, while benzotriazoles are effective against copper, their long-term ecotoxicity still needs assessment, and their synergistic protective effect on multi-metal systems such as steel is often poor. Third, although some technologies claim to be environmentally friendly, multiple additives are still required to achieve sufficient corrosion inhibition efficiency, leading to increased complexity of the overall formulation and environmental risks. Furthermore, some existing environmentally friendly vapor phase corrosion inhibitors still lag behind traditional products in terms of volatilization rate, corrosion inhibition durability, and universality to different metals, restricting their large-scale industrial application. Therefore, a green and environmentally friendly vapor phase corrosion inhibitor and its preparation method are proposed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a green and environmentally friendly vapor phase corrosion inhibitor and its preparation method. It has the advantages of renewable raw materials, low toxicity and environmental friendliness, strong compatibility with multiple metals, stable performance, and clean and low-consumption preparation process. It solves the problems of high toxicity, non-renewable raw materials, poor compatibility with multiple metals, difficulty in balancing performance and environmental protection, and unclean preparation process of current vapor phase corrosion inhibitors.

[0006] The objective of this invention can be achieved through the following technical solutions: To achieve the goals of using renewable, low-toxicity, environmentally friendly, multi-metal compatible, stable, and clean, low-consumption raw materials, this invention provides the following technical solution: a green and environmentally friendly vapor phase corrosion inhibitor, composed of the following raw materials in the indicated mass percentages: phytic acid 30%-38%, citric acid 8%-12%, diethanolamine 32%-40%, morpholine 4%-8%, water 10%-15%, ethanol 4%-6%, benzotriazole 1.5%-2.5%, and alanine ternary complex 0.5%-3.0%; The alanine ternary complex was prepared by solvent-free reaction of L-alanine, phosphoric acid and dibutylamine in a molar ratio of 1:0.8-1.2:0.8-1.2. The reaction process was as follows: L-alanine and phosphoric acid were stirred and reacted at room temperature for 8-12 minutes, and then dibutylamine was added dropwise until the product became a granular solid. After vacuum drying for 2-4 hours, the product was obtained.

[0007] Preferably, the phytic acid has a purity of ≥98% and is extracted from rice bran processing byproducts; the citric acid has a purity of ≥99% and is extracted from citrus fruits; the mass ratio of phytic acid to citric acid is 3:1-3.8:1.

[0008] Preferably, the mass ratio of diethanolamine to morpholine is 4:1-10:1; the mass ratio of water to ethanol is 2:1-3.75:1; and the mass ratio of diethanolamine to phytic acid is preferably 0.9:1-1.2:1.

[0009] Preferably, the preparation process of the alanine ternary complex further includes purification and pulverization steps: Pulverization step: The particulate solid product is washed with ethanol 2-4 times, with the amount of ethanol used each time being 1.5-2.5 times the product mass. After washing, it is vacuum dried at 40℃-50℃ for 2-4 hours, and the vacuum degree is maintained at -0.08MPa to -0.1MPa during the drying process. After drying, it is pulverized by an air jet mill, and the pulverization pressure is controlled at 0.6MPa-0.8MPa to obtain particulate product with the target particle size.

[0010] Preferably, the stirring rate during the reaction of L-alanine and phosphoric acid is 200 r / min-300 r / min, and the system temperature is monitored in real time using an infrared thermometer during the stirring process, with a deviation not exceeding ±1℃; the dropping rate of dibutylamine is 0.5 mL / min-0.8 mL / min, and the temperature of the reaction system is maintained at 20℃-25℃ during the dropping process by a constant temperature water bath, with a temperature fluctuation not exceeding ±0.5℃.

[0011] A method for preparing a green and environmentally friendly vapor phase corrosion inhibitor, based on the green and environmentally friendly vapor phase corrosion inhibitor, includes the following steps: Step 1, Dissolving and Mixing: Add the prescribed amount of water and ethanol to the reaction vessel, start stirring at a rate of 300 r / min-400 r / min, add phytic acid and citric acid, and heat to 45℃-55℃ at a rate of 2℃ / min-3℃ / min. Keep the temperature and stir for 40 minutes-60 minutes to obtain a clear solution A. Step 2, Neutralization reaction: Diethanolamine and morpholine are mixed at 20℃-25℃ for 15 minutes to obtain a mixed amine solution; under continuous stirring, the mixed amine solution is added dropwise to solution A at a rate of 0.8mL / min-1.2mL / min, and the reaction temperature is controlled at 65℃-75℃. The pH value of the system is measured every 5 minutes during the dropwise addition. When the pH value reaches 7.0-7.5, the dropwise addition is paused for 30 minutes, and then the dropwise addition is continued until the reaction is complete. Step 3, constant temperature ripening: After the addition is complete, adjust the temperature to 70℃-75℃, with the temperature fluctuation range not exceeding ±1℃. Maintain this temperature and continue stirring for 2-2.5 hours. During this period, measure the pH value every 30 minutes to ensure that the pH value of the system is stable between 7.2 and 8.0. Step 4, Cooling and Mixing: Turn off the heating and allow the system to cool naturally to 25℃-30℃. Add benzotriazole in three equal portions, with a 10-minute interval between each addition. Stir for 30 minutes until completely dissolved. Then add the alanine ternary complex and continue stirring for 40-50 minutes to obtain the mixture. Step 5, Purification and Discharge: Filter the mixture through a 0.22μm organic phase filter membrane, collect the filtrate, and conduct a stability test on the filtrate. Store the filtrate at a constant temperature of 50℃ for 72 hours. If there is no layering or sedimentation in the appearance and the corrosion inhibition efficiency decreases by ≤3%, it is considered a qualified product.

[0012] Preferably, in step 1, the solution state is observed every 15 minutes during the heat preservation and stirring process to ensure that no solid particles remain; if local clumping occurs, the stirring speed should be increased to 450 r / min and stirred continuously for 10 minutes. After stirring, the original stirring speed should be restored and the heat preservation should continue.

[0013] Preferably, in step 2, the preparation process of the mixed amine solution is carried out by magnetic stirring at a stirring rate of 150 r / min-200 r / min. During the mixing process, the dispersion uniformity is monitored by a laser particle size analyzer to ensure that the particle size distribution variation coefficient is ≤15% and there is no local high concentration phenomenon.

[0014] Preferably, in step 5, the filtrate after filtration needs to be tested for purity using high performance liquid chromatography (HPLC). The total purity of the main active ingredients, phytate ammonium salt and citrate ammonium salt, is ≥95%. The qualified product is stored in a sealed, cool, and dry environment at a temperature not exceeding 30°C, with a shelf life of not less than 12 months. For purity testing, a C18 column is used, the mobile phase is methanol-water (volume ratio 30:70), the flow rate is 1.0 mL / min, and the detection wavelength is 210 nm.

[0015] The beneficial effects of this invention are: Compared with existing technologies, this invention provides a green and environmentally friendly vapor phase corrosion inhibitor and its preparation method, which has the following beneficial effects: 1. This green and environmentally friendly vapor phase corrosion inhibitor and its preparation method use phytic acid extracted from rice bran processing by-products and citric acid from citrus fruits as core organic acid components. The polyphosphate groups of the two form a synergistic chelate system with the carboxyl groups. Combined with other green components, it breaks away from the dependence on non-renewable petrochemical products from the source of raw materials, truly realizes the green attributes of the corrosion inhibitor, and has excellent biocompatibility.

[0016] 2. This green and environmentally friendly vapor phase corrosion inhibitor and its preparation method: the alanine ternary complex, through the multi-coordination site structure formed by L-alanine, phosphoric acid and dibutylamine, synergistically works with the heterocyclic structure of benzotriazole to fill the defects of the protective film formed by the adsorption of single benzotriazole, enhance the adsorption and adaptability to different metal surfaces, and improve the synergistic protection effect of the multi-metal system.

[0017] 3. This green and environmentally friendly vapor phase corrosion inhibitor and its preparation method achieve highly efficient synergy through the complementary functional groups of phytic acid, citric acid, diethanolamine, morpholine, and other components. It can achieve excellent corrosion inhibition effect without the need to add too many auxiliary additives. While simplifying the formulation, all components are low in toxicity and have good biodegradability, reducing the overall environmental risk and conforming to the development trend of green chemistry.

[0018] 4. This green and environmentally friendly vapor phase corrosion inhibitor and its preparation method: the hydroxyl group of diethanolamine enhances water solubility, and the heterocyclic structure of morpholine improves volatility. When the two are combined, they synergistically regulate the vapor pressure of the corrosion inhibitor to a suitable range, so that the evaporation rate of the corrosion inhibitor remains stable, avoiding fluctuations in the protective effect caused by improper vapor pressure of a single component, and ensuring the continuity of pre-filming and long-term protection of the metal surface.

[0019] 5. This green and environmentally friendly vapor phase corrosion inhibitor and its preparation method, through optimized processes such as dissolution and mixing, neutralization reaction, and constant temperature curing, allow all components to fully react and cross-link. The chelation system of phytic acid and citric acid, and the adsorption complementary structure of alanine ternary complex and benzotriazole, together form a dense and stable protective film, which significantly improves the corrosion inhibition durability. At the same time, it is compatible with the surface active sites of different metals, enhancing its universality.

[0020] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the preparation method of the green and environmentally friendly vapor phase corrosion inhibitor of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Please see Figure 1 A green and environmentally friendly vapor phase corrosion inhibitor, composed of the following raw materials in the indicated weight percentages: phytic acid 30%-38%, citric acid 8%-12%, diethanolamine 32%-40%, morpholine 4%-8%, water 10%-15%, ethanol 4%-6%, benzotriazole 1.5%-2.5%, and alanine ternary complex 0.5%-3.0%; (1) Raw material preparation and selection: 1. Phytic acid is extracted from rice bran processing byproducts and purified to ensure a purity of no less than 98%. Compared with chemical synthesis methods, phytic acid extraction uses agricultural byproducts as raw materials, eliminating dependence on petroleum-based synthetic raw materials and ensuring a stable and renewable source. The extraction process is simpler, consumes less energy, and significantly reduces overall production costs. No toxic or harmful synthetic reagents are used in the production process, leaving no chemical toxicity residues. The product exhibits superior biocompatibility and biodegradability, meeting the requirements of green chemistry and environmentally friendly production. The complete steps for the extraction and preparation of phytic acid are as follows: Step 1, Raw material pretreatment: Take the defatted rice bran meal, crush it and pass it through a 40-mesh sieve to obtain rice bran meal powder; Step 2, dilute acid extraction: Mix rice bran meal powder with 0.6 mol / L hydrochloric acid solution at a solid-liquid ratio of 1:8, stir and extract at room temperature for 2 hours, filter and collect the extract; Step 3, Adsorption and Elution: Pass the extract through a D201 type anion exchange resin column, control the flow rate at 2 BV / h, and after adsorption saturation, elute with 0.8 mol / L sodium hydroxide solution and collect the eluent. Step 4, Concentration and Purification: The eluent is concentrated under reduced pressure to a solid content of 30%, activated carbon is added for decolorization at room temperature for 30 minutes, filtered, and then concentrated under reduced pressure again to obtain a purified phytic acid solution.

[0025] The purity of phytic acid was determined by high performance liquid chromatography, in accordance with the standard GB5009.152-2016. Phytic acid molecules are rich in polyphosphate groups, which can form a dense protective film by chelating metal ions, thus exhibiting excellent corrosion inhibition properties.

[0026] 2. Citric acid is extracted from citrus fruit juice byproducts, with a purification purity of no less than 99%. Compared to chemical synthesis methods, the bio-extraction and fermentation method for citric acid utilizes citrus processing byproducts as raw materials, achieving high-value utilization of agricultural waste, and the raw materials are renewable. The extraction process is mild, without high-temperature, high-pressure, or highly corrosive reactions, significantly reducing emissions of waste gas, wastewater, and solid waste. The product contains no toxic synthetic intermediates, has a higher biodegradability rate, and is more environmentally friendly. The complete steps for the extraction and preparation of citric acid are as follows: Step 1, Raw material pretreatment: Take the fruit peel and pomace by-products after juicing citrus fruits, wash and crush them, and pass them through a 20-mesh sieve to obtain citrus pomace raw material; Step 2, solid-state fermentation: Mix citrus pomace with wheat bran at a mass ratio of 4:1, adjust the moisture content to 60%, sterilize, inoculate with Aspergillus niger seed liquid, and ferment at a constant temperature of 30℃ for 72 hours to obtain fermented material; Step 3, Filtration and Impurity Removal: Add water to the fermentation material and stir to make a slurry. After plate and frame filtration, collect the filtrate. Decolorize the filtrate with activated carbon at room temperature for 30 minutes and filter to obtain a clear filtrate. Step 4, Purification and Crystallization: Add calcium carbonate emulsion to the clarified filtrate until the pH reaches 7.0 to generate calcium citrate precipitate. After filtration, acid hydrolyze the precipitate with sulfuric acid, filter to remove calcium sulfate, concentrate the acid hydrolysate, cool and crystallize, centrifuge and dry to obtain purified citric acid crystals.

[0027] The purity of citric acid was determined by high performance liquid chromatography, in accordance with the standard GB1886.235-2016. The carboxyl group in citric acid molecules can bind tightly to the active sites on the metal surface, effectively enhancing the corrosion inhibition effect, and also possessing excellent biodegradability.

[0028] 3. Diethanolamine and morpholine are selected from industrial-grade high-purity reagents. As organic amine components, they can adjust the pH value of the system and form amine salts with organic acids to enhance the volatility and adsorption of the corrosion inhibitor. Among them, the diethanolamine is selected from Dow Chemical, model DOW™ Diethanolamine, with a purity of 99.3%, and the morpholine is selected from Eastman, model Eastman™ Morpholine, with a purity ≥99.5%.

[0029] The water is deionized water, and the ethanol is industrial-grade anhydrous ethanol, which serve as solvents to ensure the dissolution and dispersion of each component. Benzotriazole is an industrial-grade reagent. The nitrogen atom in its heterocyclic structure can form a coordinate bond with a metal, which enhances the compactness of the protective film. L-alanine, phosphoric acid, and dibutylamine are all industrial-grade high-purity reagents used to prepare alanine ternary complexes.

[0030] (2) Preparation of alanine ternary complex: Accurately weigh L-alanine, phosphoric acid, and dibutylamine in a molar ratio of 1:1:1 and set aside. Add L-alanine to the reaction vessel at room temperature, start the stirring device and set the stirring speed to 250 r / min, slowly add phosphoric acid, and continue stirring for 10 minutes to allow the two to react fully and form a viscous intermediate. While keeping the stirring rate constant, add dibutylamine dropwise through a constant pressure dropping funnel at a dropping rate of 0.6 mL / min. During the dropping process, maintain the reaction system temperature at 23°C using a constant temperature water bath, with temperature fluctuations controlled within ±0.5°C, until the reaction product becomes a granular solid. The granular solid product was transferred to a vacuum drying oven and dried for 3 hours under a vacuum of -0.09 MPa. It was then washed three times with ethanol, each time using twice the mass of the product. After washing, it was dried again for 3 hours at 45°C and a vacuum of -0.085 MPa. The dried product was pulverized by an air jet mill, with the pulverization pressure controlled at 0.7 MPa, to obtain alanine ternary complex powder with the target particle size.

[0031] The core of the molecular structure of this complex is: the amino group of L-alanine forms a coordination bond with the phosphate group of phosphate, and the amino group of dibutylamine provides an additional coordination site. The three are connected by chemical bonds to form an "amino-phosphate group-amino" synergistic coordination structure, which can form a stable complex with the empty orbitals of metals and enhance the adsorption capacity of the corrosion inhibitor on multi-metal surfaces.

[0032] A method for preparing a green and environmentally friendly vapor phase corrosion inhibitor, based on the green and environmentally friendly vapor phase corrosion inhibitor, includes the following steps: Step 1, Dissolving and Mixing: Add the prescribed amount of water and ethanol to the reaction vessel, start stirring at a rate of 300 r / min-400 r / min, add phytic acid and citric acid, and heat to 45℃-55℃ at a rate of 2℃ / min-3℃ / min. Keep the temperature and stir for 40 minutes-60 minutes to obtain a clear solution A. Step 2, Neutralization reaction: Diethanolamine and morpholine are mixed at 20℃-25℃ for 15 minutes to obtain a mixed amine solution; under continuous stirring, the mixed amine solution is added dropwise to solution A at a rate of 0.8mL / min-1.2mL / min, and the reaction temperature is controlled at 65℃-75℃. The pH value of the system is measured every 5 minutes during the dropwise addition. When the pH value reaches 7.0-7.5, the dropwise addition is paused for 30 minutes, and then the dropwise addition is continued until the reaction is complete. Step 3, constant temperature ripening: After the addition is complete, adjust the temperature to 70℃-75℃, with the temperature fluctuation range not exceeding ±1℃. Maintain this temperature and continue stirring for 2-2.5 hours. During this period, measure the pH value every 30 minutes to ensure that the pH value of the system is stable between 7.2 and 8.0. Step 4, Cooling and Mixing: Turn off the heating and allow the system to cool naturally to 25℃-30℃. Add benzotriazole in three equal portions, with a 10-minute interval between each addition. Stir for 30 minutes until completely dissolved. Then add the alanine ternary complex and continue stirring for 40-50 minutes to obtain the mixture. Step 5, Purification and Discharge: Filter the mixture through a 0.22μm organic phase filter membrane, collect the filtrate, and conduct a stability test on the filtrate. Store the filtrate at a constant temperature of 50℃ for 72 hours. If there is no layering or sedimentation in the appearance and the corrosion inhibition efficiency decreases by ≤3%, it is considered a qualified product.

[0033] Example 1 Step 1, 1. Dissolve and mix: Add 12% water and 5% ethanol to a 500mL reaction vessel according to the formula. Start the stirring device and set the stirring speed to 350r / min. Add 35% phytic acid and 10% citric acid in sequence. Turn on the heating device and heat to 50℃ at a heating rate of 2.5℃ / min. Keep the temperature and stir for 50 minutes. During the holding period, observe the state of the solution every 15 minutes. If local agglomeration is found, increase the stirring speed to 450r / min and continue stirring for 10 minutes. Then return to 350r / min to ensure that there are no solid particles left. Finally, a clear solution A is obtained. This step controls the heating and stirring rates to avoid agglomeration caused by excessively high local concentrations of phytic acid and citric acid. Heating to 45 to 55°C accelerates their dissolution, while maintaining the temperature and stirring ensures that the molecules are fully dispersed and the solution transmittance is not less than 98%, laying the foundation for a homogeneous system for subsequent reactions.

[0034] Step 2, Neutralization reaction: Diethanolamine (30% by mass) and morpholine (5% by mass) were added to a beaker at 23℃ and stirred at 180 r / min for 15 minutes using a magnetic stirrer to prepare a mixed amine solution. During the stirring process, the dispersion uniformity was monitored using a laser particle size analyzer to ensure that the particle size distribution variation coefficient did not exceed 15%. While keeping solution A stirred, add the mixed amine solution dropwise to solution A at a rate of 1.0 mL / min through a constant pressure dropping funnel, while controlling the temperature of the reaction system at 70℃. During the dropwise addition, the pH value of the system was measured with a pH meter every 5 minutes. When the pH reached 7.2, the dropwise addition was paused for 30 minutes to allow the reaction to proceed fully. Then the dropwise addition was continued until the mixed amine solution was completely added. Controlling the dropping rate and reaction temperature can prevent local over-alkaliness caused by an overly vigorous neutralization reaction. Too fast a dropping rate can cause pH abrupt changes and amine salt decomposition. In this embodiment, the pH fluctuation does not exceed ±0.3, the amine salt conversion rate is not less than 98%, and the loss of corrosion inhibitory active ingredients does not exceed 2%.

[0035] Step 3: Constant temperature ripening: After the addition is complete, adjust the heating device to stabilize the system temperature at 72℃, with the temperature fluctuation range controlled within ±0.5℃. Maintain this temperature and continue stirring the reaction for 2.2 hours. During this period, measure the pH value every 30 minutes to ensure that the pH of the system is stable between 7.5 and 7.8. If the pH is lower than 7.5, add a small amount of diethanolamine to adjust it; if it is higher than 7.8, add a small amount of citric acid to adjust it. Constant temperature curing can promote the full reaction and cross-linking of corrosion inhibitory active ingredients. When the curing is not done or the curing time is insufficient, the content of active ingredients is only 85%. After curing, the content of active ingredients is not less than 95%, the product stability is improved, and the corrosion inhibition efficiency decreases by no more than 1% after 72 hours of constant temperature storage at 50℃.

[0036] Step 4: Cooling and compounding: Turn off the heating device and allow the system to cool naturally to 28°C. Add 2% benzotriazole in three equal portions, 10 minutes apart, and stir for 30 minutes after each addition until completely dissolved. Add 2% alanine ternary complex and continue stirring for 45 minutes. During this time, observe the solution with the naked eye to ensure that no precipitate is formed, and obtain a homogeneous mixture. Adding benzotriazole in stages can prevent its aggregation and synergistic adsorption with the alanine ternary complex. When benzotriazole is added all at once, the incomplete dissolution rate is 10%, while after adding it in stages, the incomplete dissolution rate is no more than 1%, the uniformity of the mixture is improved, and the subsequent filtration pass rate is no less than 99%.

[0037] Step 5: Purification and Discharge: The mixture was subjected to reduced-pressure filtration through a 0.22-μm organic phase filter membrane, and the filtrate was collected. The purity of the filtrate was detected by high-performance liquid chromatography. The chromatographic column was a C18 column, the mobile phase was methanol-water with a volume ratio of 30:70, the flow rate was 1.0 mL / min, and the detection wavelength was 210 nm, ensuring that the total purity of the phytic acid amine salt and the citric acid amine salt was not less than 95%. The stability of the filtrate was tested. It was stored at a constant temperature of 50 °C for 72 hours. If there was no stratification or precipitation in the appearance and the decline rate of the corrosion inhibition efficiency did not exceed 3%, it was a qualified product. The qualified product was sealed and stored in a cool and dry environment, with the storage temperature controlled at 25 °C and the shelf life not less than 12 months. Filtration and purity detection could remove impurities and unreacted raw materials. The impurity content in the unfiltered product was not less than 5%, and the impurity content after filtration did not exceed 0.5%. The stability of the corrosion inhibition effect of the product was improved, and there was no deterioration during storage.

[0038] Above: In the preferred range where the mass ratio of the synergy between phytic acid and citric acid is controlled at 3.5:1, the polyphosphate groups of phytic acid and the carboxyl groups of citric acid form a synergistic chelation system, which can simultaneously adsorb on multiple active sites on the metal surface, significantly improving the coverage of the protective film. There are pores in the single phytic acid protective film, and the adsorption force of single citric acid is weak. After the two are compounded, the porosity decreases and the corrosion inhibition efficiency increases. The synergy between diethanolamine and morpholine is controlled in the preferred range of 6:1. The hydroxyl groups of diethanolamine enhance water solubility, and the heterocyclic structure of morpholine improves volatility. After the two are compounded, the vapor pressure of the corrosion inhibitor can be adjusted to be in the appropriate range of 10 -5 to 10 -6 mmHg. The vapor pressure of single diethanolamine is too low, and the vapor pressure of single morpholine is too high. After compounding, the evaporation rate of the corrosion inhibitor is stable, the pre-filming time on the metal surface is shortened, and the protection period is extended. The synergistic effect of the alanine ternary complex. The heteroatoms such as N and P in its molecule can provide lone pair electrons to form stable coordination bonds with metal empty orbitals. At the same time, it synergistically fills the defects of the protective film with the heterocyclic structure of benzotriazole. Benzotriazole forms a single-site adsorption with the metal through the heterocyclic nitrogen atom, while the multi-coordination site structure of the alanine ternary complex can form adsorption complementarity with benzotriazole, reducing the pores in the protective film.

[0039] To further verify the comprehensive performance advantages of this corrosion inhibitor composition, clarify the necessity of the core component alanine ternary complex, and at the same time form a performance comparison with traditional gas-phase corrosion inhibitors, this embodiment designs multiple control experiments, and systematically tests the corrosion inhibition efficiency, environmental protection, multi-metal adaptability and storage stability of each group of samples according to relevant national standards, providing empirical support for the superiority of the technical solution.

[0040] I. Experimental scheme: Experimental group: The green and environmentally friendly vapor phase corrosion inhibitor described in this application was prepared according to Example 1, with the following component ratio: 35% phytic acid, 10% citric acid, 30% diethanolamine, 5% morpholine, 12% water, 5% ethanol, 2% benzotriazole, and 2% alanine ternary complex. Control group 1: Traditional nitrite corrosion inhibitor dicyclohexylamine nitrite, industrial grade; Control group 2: Traditional organic amine compound corrosion inhibitors benzotriazole and cyclohexylamine, mass ratio 1:4; Control group 3: Composition lacking alanine ternary complex, with other components and proportions completely consistent with the experimental group; Test objects: 45# steel test pieces and copper test pieces, both with dimensions of 40mm×60mm×3mm; Testing standards: Compliance with standards such as GB / T35491, GB / T16266, GB / T27861, and GB / T20397.

[0041] II. Experimental Procedure: Corrosion inhibition efficiency test: Weigh 0.1g of each corrosion inhibitor sample and place it in the weighing bottle at the bottom of the wide-mouth bottle. Hang the polished and cleaned test piece in the wide-mouth bottle, with the distance from the bottom of the rubber stopper to the top of the test piece being 50mm. First, place the wide-mouth bottle in a 30℃ incubator for 18h, then at room temperature for 1h, add 20mL of water to maintain a humid environment, then place it in a 5℃ incubator for 2h, and finally place it in a 50℃ constant temperature drying oven for 3h. After the experiment, observe the surface condition of the test piece and calculate the corrosion inhibition efficiency.

[0042] Toxicity testing: Acute toxicity testing was conducted according to GB / T27861 to detect whether carcinogenic substances were present and to determine the median lethal dose (LD50).

[0043] Biodegradability test: Under the conditions of 25℃ and pH=7.0, each corrosion inhibitor was placed in activated sludge and cultured for 28 days, and the biodegradation rate was measured.

[0044] Multi-metal compatibility test: 45# steel, copper and galvanized steel test pieces were placed in the same sealed environment, and each corrosion inhibitor was added. The test pieces were left at room temperature for 6 months and the corrosion was observed.

[0045] Storage stability test: Each corrosion inhibitor was sealed and stored at 30°C for 12 months. The appearance changes were observed and the rate of decrease in corrosion inhibition efficiency was measured.

[0046] III. Experimental Data: The experimental data above show that the corrosion inhibition efficiency of the experimental group on 45# steel is comparable to that of control group 1, but the corrosion inhibition efficiency on copper is significantly higher than that of control group 1 and control group 3, and also better than control group 2. Control group 3 differs from the experimental group only in the alanine ternary complex component, but its corrosion inhibition efficiency on copper decreased from 95.2% to 86.0%, and its multi-metal compatibility also decreased. This clearly demonstrates that the alanine ternary complex plays a key role in improving the corrosion inhibition effect of the composition on non-ferrous metals and its multi-metal compatibility, and is not a dispensable component.

[0047] In terms of toxicity, no carcinogens were detected in either the experimental group or the control group 3, and the median lethal dose was much higher than that of the control groups 1 and 2, indicating better safety. The biodegradation rate of the experimental group was similar to that of the control group 3, both close to 90%, which was much higher than that of the control groups 1 and 2, indicating that the introduction of the alanine ternary complex does not affect the environmental friendliness of the composition. In terms of storage stability, the experimental group showed no change in appearance within 12 months and the corrosion inhibition efficiency decreased by only 2.1%, which was better than the 4.8% of the control group 3 and the other two control groups, indicating higher reliability in long-term use.

[0048] This embodiment demonstrates through systematic comparative experiments that the present invention is superior to traditional vapor phase corrosion inhibitors in terms of corrosion inhibition efficiency, environmental friendliness, multi-metal compatibility, and storage stability. The introduction of alanine ternary complex is the key to improving multi-metal compatibility and corrosion inhibition efficiency and stability. Without this component, the corrosion inhibition effect of the composition on copper is significantly reduced, confirming the necessity of this component. The core advantages of this invention stem from the green and renewable characteristics of the raw materials, the synergistic design of each component, and the optimized preparation process. It not only solves the toxicity problem of traditional nitrite corrosion inhibitors, but also overcomes the defects of traditional organic amine compound corrosion inhibitors, such as poor multi-metal compatibility and insufficient storage stability, and has broad application prospects.

[0049] In summary, this green and environmentally friendly vapor phase corrosion inhibitor and its preparation method use phytic acid extracted from rice bran processing byproducts and citric acid from citrus fruits as core organic acid components. The polyphosphate groups of these two components form a synergistic chelate system with the carboxyl groups. Combined with other green components, this method eliminates the dependence on non-renewable petrochemical products from the source of raw materials, truly realizing the green properties of the corrosion inhibitor, and exhibiting excellent biocompatibility.

[0050] Furthermore, this green and environmentally friendly vapor phase corrosion inhibitor and its preparation method utilize the multi-coordination site structure formed by L-alanine, phosphoric acid, and dibutylamine in the alanine ternary complex. This synergistic effect with the heterocyclic structure of benzotriazole fills the defects of the protective film formed by the adsorption of benzotriazole alone, enhances the adsorption and compatibility with different metal surfaces, and improves the synergistic protection effect of the multi-metal system.

[0051] Furthermore, this green and environmentally friendly vapor phase corrosion inhibitor and its preparation method achieve highly efficient synergy through the complementary functional groups of various components such as phytic acid and citric acid, diethanolamine and morpholine. It can achieve excellent corrosion inhibition effect without the need to add too many auxiliary additives. While simplifying the formulation, all components are low in toxicity and have good biodegradability, reducing the overall environmental risk and conforming to the development trend of green chemistry.

[0052] Furthermore, this green and environmentally friendly vapor phase corrosion inhibitor and its preparation method utilize the hydroxyl groups of diethanolamine to enhance water solubility and the heterocyclic structure of morpholine to improve volatility. When these two are combined, they synergistically regulate the vapor pressure of the corrosion inhibitor to a suitable range, keeping the evaporation rate of the corrosion inhibitor stable. This avoids fluctuations in the protective effect caused by improper vapor pressure of a single component, ensuring the continuity of pre-filming and long-term protection of the metal surface.

[0053] Furthermore, this green and environmentally friendly vapor phase corrosion inhibitor and its preparation method, through optimized processes such as dissolution and mixing, neutralization reaction, and constant temperature curing, allow all components to fully react and cross-link. The chelation system of phytic acid and citric acid, and the adsorption complementary structure of alanine ternary complex and benzotriazole, together form a dense and stable protective film, significantly improving corrosion inhibition durability. At the same time, it adapts to the surface active sites of different metals, enhancing its universality. This solves the problems of high toxicity, non-renewable raw materials, poor multi-metal compatibility, difficulty in balancing performance and environmental protection, and unclean preparation processes that exist in current vapor phase corrosion inhibitors.

[0054] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A green and environment-friendly gas-phase corrosion inhibitor, characterized in that, It is composed of the following raw materials in the indicated weight percentages: phytic acid 30%-38%, citric acid 8%-12%, diethanolamine 32%-40%, morpholine 4%-8%, water 10%-15%, ethanol 4%-6%, benzotriazole 1.5%-2.5%, and alanine ternary complex 0.5%-3.0%. The alanine ternary complex was prepared by solvent-free reaction of L-alanine, phosphoric acid and dibutylamine in a molar ratio of 1:0.8-1.2:0.8-1.

2. The reaction process was as follows: L-alanine and phosphoric acid were stirred and reacted at room temperature for 8-12 minutes, and then dibutylamine was added dropwise until the product became a granular solid. After vacuum drying for 2-4 hours, the product was obtained.

2. The green environment-friendly gas-phase corrosion inhibitor according to claim 1, characterized in that, The phytic acid has a purity of ≥98% and is extracted from rice bran processing byproducts; the citric acid has a purity of ≥99% and is extracted from citrus fruits; the mass ratio of phytic acid to citric acid is 3:1-3.8:

1.

3. The green environment-friendly gas-phase corrosion inhibitor according to claim 1, characterized in that, The mass ratio of diethanolamine to morpholine is 4:1-10:1; the mass ratio of water to ethanol is 2:1-3.75:1; and the mass ratio of diethanolamine to phytic acid is 0.9:1-1.2:

1.

4. The green environment-friendly gas-phase corrosion inhibitor according to claim 1, characterized in that, The preparation process of the alanine ternary complex also includes purification and pulverization steps: the particulate solid product is washed with ethanol 2-4 times, with the amount of ethanol used each time being 1.5-2.5 times the mass of the product. After washing, it is vacuum dried at 40℃-50℃ for 2-4 hours, and the vacuum degree is maintained at -0.08MPa to -0.1MPa during the drying process. After drying, it is pulverized by an air jet mill, and the pulverization pressure is controlled at 0.6MPa-0.8MPa to obtain particulate product with the target particle size.

5. The green environment-friendly gas-phase corrosion inhibitor according to claim 4, characterized in that, The stirring rate during the reaction of L-alanine and phosphoric acid was 200 r / min-300 r / min. During the stirring process, the system temperature was monitored in real time using an infrared thermometer, with a deviation not exceeding ±1℃. The dropping rate of dibutylamine was 0.5 mL / min-0.8 mL / min. During the dropping process, the reaction system temperature was maintained at 20℃-25℃ using a constant temperature water bath, with temperature fluctuations not exceeding ±0.5℃.

6. A method for preparing a green and environmentally friendly gas-phase corrosion inhibitor, characterized in that, Based on the green and environmentally friendly vapor phase corrosion inhibitor described in claims 1-5, the steps are as follows: Step 1, Dissolving and Mixing: Add the prescribed amount of water and ethanol to the reaction vessel, start stirring at a rate of 300 r / min-400 r / min, add phytic acid and citric acid, and heat to 45℃-55℃ at a rate of 2℃ / min-3℃ / min. Keep the temperature and stir for 40 minutes-60 minutes to obtain a clear solution A. Step 2, Neutralization reaction: Mix the prescribed amount of diethanolamine and morpholine at 20℃-25℃ for 15 minutes to obtain a mixed amine solution; under continuous stirring, add the mixed amine solution dropwise to solution A at a rate of 0.8mL / min-1.2mL / min, control the reaction temperature to be maintained at 65℃-75℃, measure the pH value of the system every 5 minutes during the dropwise addition, when the pH value reaches 7.0-7.5, pause the dropwise addition for 30 minutes, and then continue the dropwise addition until it is completed; Step 3, constant temperature ripening: After the addition is complete, adjust the temperature to 70℃-75℃, with the temperature fluctuation range not exceeding ±1℃. Maintain this temperature and continue stirring for 2-2.5 hours. During this period, measure the pH value every 30 minutes to ensure that the pH value of the system is stable between 7.2 and 8.

0. Step 4, Cooling and Mixing: Turn off the heating and allow the system to cool naturally to 25℃-30℃. Add benzotriazole in three equal portions, with a 10-minute interval between each addition. Stir for 30 minutes until completely dissolved. Then add the alanine ternary complex and continue stirring for 40-50 minutes to obtain the mixture. Step 5, Purification and Discharge: Filter the mixture through a 0.22μm organic phase filter membrane, collect the filtrate, and conduct a stability test on the filtrate. If the filtrate is stored at a constant temperature of 50℃ for 72 hours and shows no layering or precipitation, and the corrosion inhibition efficiency decreases by ≤3%, it is considered a green and environmentally friendly vapor phase corrosion inhibitor.

7. The method according to claim 6, characterized in that, In step 1, the solution state is observed every 15 minutes during the heat preservation and stirring process to ensure that no solid particles remain. If local clumping occurs, the stirring speed should be increased to 450 r / min and stirred continuously for 10 minutes. After stirring, the original stirring speed should be restored and the solution should be kept warm.

8. The method for preparing a green and environmentally friendly vapor phase corrosion inhibitor according to claim 6, characterized in that, In step 2, the preparation process of the mixed amine solution is carried out by magnetic stirring at a stirring rate of 150 r / min-200 r / min. During the mixing process, the dispersion uniformity is monitored by a laser particle size analyzer to ensure that the particle size distribution variation coefficient is ≤15% and there is no local high concentration phenomenon.

9. The method for preparing a green and environmentally friendly vapor phase corrosion inhibitor according to claim 6, characterized in that, In step 5, the filtrate after filtration needs to be tested for purity using high performance liquid chromatography (HPLC). The total purity of the main active ingredients, phytate ammonium salt and citrate ammonium salt, should be ≥95%. The prepared green and environmentally friendly gas phase corrosion inhibitor should be stored in a sealed, cool, and dry environment at a temperature not exceeding 30°C, with a shelf life of not less than 12 months. For purity testing, a C18 column should be used, with methanol-water as the mobile phase (volume ratio 30:70), a flow rate of 1.0 mL / min, and a detection wavelength of 210 nm.

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