A main agent for a non-phosphorus corrosion inhibitor and a non-phosphorus corrosion inhibitor based thereon, a preparation method and applications

Abstract

The application discloses a kind of main agent for phosphorus-free corrosion inhibitor and phosphorus-free corrosion inhibitor based thereon, preparation method and application, belong to the technical field of corrosion inhibitor.The main agent is 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazole-5-amine. In terms of mass percentage, the raw materials of the phosphorus-free corrosion inhibitor include 2.0% to 12.0% of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazole-5-amine, 1.0% to 2.0% of L-methionine, 0.5% to 1.0% of benzotriazole, 0.3% to 2.0% of dodecyl dimethyl betaine and 3.0% to 5.0% of ethylene glycol, and the balance is brine except salt.The phosphorus-free corrosion inhibitor provided by the application can solve the technical problems of existing corrosion inhibitors, such as environmental pollution and poor binding ability of corrosion inhibitors with metal surfaces in pickling environment and at high temperatures.

Description

Technical Field

[0001] This invention belongs to the field of corrosion inhibitor technology, specifically relating to a phosphorus-free corrosion inhibitor main agent, a phosphorus-free corrosion inhibitor based thereon, its preparation method, and its application. Background Technology

[0002] Pickling with EDTA, formic acid + glycolic acid, and citric acid is widely used in the chemical cleaning of power plant boilers due to its simple cleaning system and good oxide scale removal effect. According to the guidelines for chemical cleaning of boilers in thermal power plants, the cleaning cycle time of the pickling solution is usually 24-48 hours, therefore a certain mass fraction of corrosion inhibitor must be added to suppress corrosion. In recent years, the use of ionic surfactants in the formulation of pickling corrosion inhibitors has become widespread. These inhibitor components dissociate into surface-active ions in water, which are then adsorbed onto the metal surface during the cleaning cycle through physical or chemical adsorption. This prevents secondary corrosion of the active metal surface exposed during pickling by the chemical cleaning solution, thus ensuring the quality of the pickling process.

[0003] However, these mainstream organic acid corrosion inhibitors have some drawbacks. On the one hand, after acid washing of power plant boilers, the waste liquid containing phosphorus corrosion inhibitors often causes biotoxicity. For example, although phosphate ester corrosion inhibitors such as diethylenetriamine pentamethylphosphonic acid (DTPMP), hydroxyethylidene diphosphonic acid (HEDP), and aminotrimethylphosphonic acid (ATPM) have good corrosion inhibition effects, improper waste liquid treatment can cause environmental pollution. On the other hand, at high acid washing temperatures (such as EDTA cleaning), the adsorption performance of corrosion inhibitor components without strong polar bonds such as carbon-phosphorus bonds on the austenitic steel surface is somewhat lacking. For example, commonly used imidazoline quaternary ammonium salt corrosion inhibitors have poor bonding ability with the metal surface under high-temperature acid washing, resulting in poor corrosion inhibition performance when the acid washing time is long.

[0004] In conclusion, it is of great significance to study new environmentally friendly corrosion inhibitors with strong metal-binding properties suitable for acid washing of power plant boilers. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a phosphorus-free corrosion inhibitor main agent, a phosphorus-free corrosion inhibitor based thereon, a preparation method and an application thereof, so as to solve the technical problems of existing corrosion inhibitors having large environmental pollution and poor bonding ability between the corrosion inhibitor and the metal surface in pickling environment and at high temperature.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] The first aspect of the present invention provides a main agent, wherein the main agent is 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine;

[0008] The structural formula of the 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is as follows:

[0009]

[0010] The second aspect of the present invention provides the application of the aforementioned main agent, specifically the application of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazole-5-amine in the preparation of phosphorus-free corrosion inhibitors.

[0011] A third aspect of the present invention provides a phosphorus-free corrosion inhibitor. Based on the main agent, the raw materials of the phosphorus-free corrosion inhibitor, by mass percentage, include 2.0% to 12.0% of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, 1.0% to 2.0% of L-methionine, 0.5% to 1.0% of benzotriazole, 0.3% to 2.0% of dodecyl dimethyl betaine, and 3.0% to 5.0% of ethylene glycol, with the balance being demineralized water.

[0012] A fourth aspect of this invention provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0013] The deionized water is heated to 50-70°C. Dodecyl dimethyl betaine is added while stirring. After it dissolves, L-methionine and benzotriazole are added, followed by ethylene glycol. After stirring evenly, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor.

[0014] In the specific implementation process, the preparation process of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is as follows:

[0015] Under nitrogen protection at room temperature, anhydrous ethanol and sodium ethoxide were stirred until dissolved, and 3-amino-5-mercapto-1,2,4-triazole was slowly added while stirring to obtain a thiolate solution.

[0016] Under zero-degree and nitrogen protection, the thiolate solution was added to the anhydrous ethanol solution of N,N-diethylchloroethylamine to carry out the reaction. The reaction was quenched with water and the anhydrous ethanol was removed by vacuum distillation. Then, the reaction was carried out by extraction, drying, vacuum distillation and purification to obtain 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine.

[0017] Under nitrogen protection at room temperature, anhydrous ethanol, potassium carbonate, and sodium iodide were stirred until dissolved, and then bromoethane and 5-((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine were added sequentially. The mixture was gradually heated to the set temperature with stirring, quenched with water, and the anhydrous ethanol was removed by vacuum distillation. The mixture was then subjected to extraction, drying, vacuum distillation, and purification to obtain 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine.

[0018] In the specific implementation process, the molar ratio of 3-amino-5-mercapto-1,2,4-triazole, sodium ethoxide and N,N-diethylchloroethylamine is 1:(1.5-2):(1-1.2).

[0019] In the specific implementation process, the molar ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, potassium carbonate, sodium iodide and bromoethane is 1:(2~6):(1~2):1.

[0020] In the specific implementation process, the ratio of 3-amino-5-mercapto-1,2,4-triazole to anhydrous ethanol is 100g:2-5L; the ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazole-3-amine to anhydrous ethanol is 100g:2-5L; the reaction temperature of the thiolate solution and the anhydrous ethanol solution of N,N-diethylchloroethylamine is 50-60℃, and the reaction stirring time is 48-72h; the set temperature is 50-70℃, and the stirring time is 12-48h.

[0021] The fifth aspect of this invention provides the application of a phosphorus-free corrosion inhibitor in the acid washing process of a power plant boiler.

[0022] In specific implementation, the phosphorus-free corrosion inhibitor is suitable for pickling media with a mass fraction of less than 10%; the pickling medium is any one of a mixture of glycolic acid and formic acid, citric acid and EDTA; the mass fraction of the phosphorus-free corrosion inhibitor added during the pickling process of power plant boilers is 0.3% to 0.6%.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention provides a main agent, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, which mainly relies on the adsorption of N and S atoms in its molecule onto the carbon steel surface. The S atom has less steric hindrance, thus facilitating contact with the metal surface. Furthermore, after adsorption, the three ethyl groups on the molecule provide a certain degree of hydrophobicity, making the adsorption more stable.

[0025] This invention provides, on the one hand, the application of the main agent in phosphorus-free corrosion inhibitors, which utilizes the easy metal contact and adsorption stability of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine to enhance the metal adsorption capacity of phosphorus-free corrosion inhibitors.

[0026] In another aspect, this invention provides a phosphorus-free corrosion inhibitor. Firstly, the main component of this phosphorus-free corrosion inhibitor, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, has a high electron density and low steric hindrance in its sulfur and nitrogen atoms, making it more capable of donating electrons to the metal as a Lewis base. Upon contact with the metal surface, the lone pair electrons of the heteroatom in the main component form strong coordinate bonds with the empty orbitals of the iron atom. Simultaneously, the short alkyl chain on the triazole aromatic ring has a certain hydrophobic effect, making it easier for the heteroatom side to approach the metal surface, thus allowing for more robust adhesion. Secondly, the nitrogen and sulfur atoms containing lone pairs of electrons in the main agent 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine molecule have relatively low overall steric hindrance, allowing it to produce a synergistic effect with the other components when adsorbed onto the metal. For example, ethylene glycol can be well dispersed in the pickling solution to coat the surface of metal atoms and can form hydrogen bonds with the amino hydrogen atoms of the main agent and methionine molecules, thus improving the performance of the corrosion inhibitor in the pickling of power plant boilers. The addition of quaternary ammonium salt ionic compounds such as dodecyl dimethyl betaine also provides good compatibility, acting as a phase transfer agent to make other corrosion inhibitor components more tightly and uniformly distributed on the metal surface. The corrosion inhibitor forms a dense film with the metal, avoiding corrosion from ferric ions and hydrogen ions in the pickling solution. In addition, the above-mentioned phosphorus-free corrosion inhibitor formulation does not contain phosphorus, is easily degraded in wastewater treatment, and is a green, stable, and highly efficient corrosion inhibitor.

[0027] The aforementioned phosphorus-free corrosion inhibitor is applied in the acid washing process of power plant boilers. The phosphorus-free corrosion inhibitor provided by this invention exhibits excellent corrosion inhibition performance and is not easily decomposed in the acid washing environment or at high temperatures. Furthermore, the phosphorus-free corrosion inhibitor provided by this invention has low biotoxicity in wastewater treatment and causes minimal environmental pollution. Attached Figure Description

[0028] Figure 1 This is a synthetic route diagram for the main agent used in the phosphorus-free corrosion inhibitor of the present invention;

[0029] Figure 2 This is an adsorption model diagram of the main agent molecule used in the phosphorus-free corrosion inhibitor of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0032] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0033] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0034] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0035] This invention provides a phosphorus-free corrosion inhibitor base, a phosphorus-free corrosion inhibitor based thereon, a preparation method, and its application.

[0036] The formulation design process of phosphorus-free corrosion inhibitors is as follows: For corrosion inhibitors to be effective, the molecular design of their organic components should be based on improving the bonding ability between corrosion inhibitor molecules and metals, that is, enhancing the bonding ability between organic molecules and metals. This is because the tight bonding between the corrosion inhibitor and the metal surface allows it to be fully and tightly stored on the active sites of the metal, forming a blocking effect and reducing the corrosion effect of ferric ions and hydrogen ions on the metal surface. The strength of the organic-metal bond between corrosion inhibitor components and the pipe surface is mainly influenced by the following factors: 1) According to the Lewis acid-base theory, when an organic corrosion inhibitor takes effect, the organic component molecule, acting as a Lewis base, provides lone pairs of electrons to the unoccupied d orbitals of the metal. This requires a higher electron density in the active part of the corrosion inhibitor component molecule, making it easier to donate electrons and improve the interaction between nitrogen-containing atoms and iron atoms. According to molecular orbital theory and density functional theory, for various nitrogen-containing (non-phosphorus) organic compound molecules, their HOMO orbitals (highest occupied molecular orbitals) are generally distributed mainly in the π orbitals near nitrogen and sulfur atoms. When the electron density of these nitrogen or sulfur atoms is higher, they have higher HOMO energy levels, which represent a lower oxidation potential and easier electron loss, also meaning a higher binding rate between the organic corrosion inhibitor molecule and the metal. 2) The component molecule should have heteroatom sites with low steric hindrance that are easy to contact the metal surface, making heteroatoms more inclined to contact the metal. 3) As a compound component, the components should have a greater tendency to form hydrogen bonds with other components, making them more miscible and increasing the effect of compound use.

[0037] Therefore, the first aspect of the present invention provides a main agent, which is 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, with the following structural formula:

[0038]

[0039] The above-mentioned main agent 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine (C 10 H 21 The NMR test data for N5S are as follows:

[0040] (C 10 H 21 N5S): 1 H NMR (400MHz, CDCl3, δ): 6.71 (s, 2H), 3.88 (dd, J=5.6, 2.8Hz, 2H), 3.51 (t, J=1.6, 2H ),3.05(dd,J=4.8,2.8Hz,4H),2.69(t,J=3.6,2H),1.52(s,3H),1.16(t,J=2.4,6H); 13C NMR (100MHz, CDCl3, δ): 160.21, 157.54, 56.33, 48.55, 17.02, 13.51.

[0041] like Figure 2 The diagram shows the adsorption model of the corrosion inhibitor's main component molecule on a carbon steel surface. Based on the molecular structure of the main component, it can be seen that it mainly relies on the N and S atoms in the molecule to adsorb onto the carbon steel surface. The S atoms have less steric hindrance, thus making it easier for them to contact the metal surface. Furthermore, after adsorption, the three ethyl groups on the molecule provide a certain degree of hydrophobicity, making the adsorption more stable.

[0042] The second aspect of the present invention provides the application of the main agent 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazole-5-amine in phosphorus-free corrosion inhibitors.

[0043] A third aspect of this invention provides a phosphorus-free corrosion inhibitor, using the aforementioned phosphorus-free corrosion inhibitor main agent. By mass percentage, the raw materials of the phosphorus-free corrosion inhibitor include 2.0%–12.0% of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, 1.0%–2.0% of L-methionine, 0.5%–1.0% of benzotriazole, 0.3%–2.0% of dodecyl dimethyl betaine, and 3.0%–5.0% of ethylene glycol, with the balance being demineralized water.

[0044] The main component of this corrosion inhibitor has a high electron density and low steric hindrance on its sulfur and nitrogen atoms, which enhances its ability to donate electrons to the metal. The other end has an alkyl chain that acts as a hydrophobic agent. The synergistic effect of the several compound components increases solubility and allows the corrosion inhibitor molecules to form hydrogen bonds when they adhere to the metal surface, resulting in stronger coordination and better corrosion inhibition.

[0045] The corrosion inhibition mechanism of the phosphorus-free corrosion inhibitor provided by this invention is as follows: The sulfur and nitrogen atoms of the main component of the corrosion inhibitor have high electron density and low steric hindrance, making them more capable of donating electrons to the metal as Lewis bases. Upon contact with the metal surface, the lone pairs of electrons of the heteroatoms in the main component molecule form strong coordinate bonds with the empty orbitals of the iron atoms. Simultaneously, the short alkyl chains on the triazole aromatic ring have a certain hydrophobic effect, making it easier for the heteroatoms to approach the metal surface, thus allowing for stronger adhesion. Secondly, the overall steric hindrance near the nitrogen and sulfur atoms containing lone pairs of electrons in the main component molecule is low, which can produce a synergistic effect with the other components when adsorbed onto the metal. For example, ethylene glycol can be well dispersed in the pickling solution to coat the metal atom surface and can form hydrogen bonds with the amino hydrogen atoms of the main component and methionine molecules, thus improving the performance of the corrosion inhibitor during the pickling of power plant boilers. The addition of quaternary ammonium salt ionic compounds such as dodecyl dimethyl betaine also provides good compatibility, acting as a phase transfer agent, allowing other corrosion inhibitor components to be more tightly and uniformly distributed on the metal surface. The corrosion inhibitor forms a dense film with the metal, preventing corrosion from ferric ions and hydrogen ions in the pickling solution. The aforementioned phosphorus-free corrosion inhibitor demonstrated excellent corrosion inhibition performance in actual testing and evaluation. Being phosphorus-free, it has minimal environmental pollution, making it a green and highly efficient corrosion inhibitor.

[0046] A fourth aspect of this invention provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0047] The deionized water is heated to 50-70°C. Dodecyl dimethyl betaine is added while stirring. After it dissolves, L-methionine and benzotriazole are added, followed by ethylene glycol. After stirring evenly, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor.

[0048] like Figure 1 As shown, the preparation method of the main agent 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine for the above-mentioned phosphorus-free corrosion inhibitor includes the following steps:

[0049] S1: Under room temperature and nitrogen protection, anhydrous ethanol and sodium ethoxide are stirred until dissolved, and 3-amino-5-mercapto-1,2,4-triazole is slowly added and stirred to react to obtain a thiolate solution; wherein, the ratio of 3-amino-5-mercapto-1,2,4-triazole to anhydrous ethanol is 100g:2~5L.

[0050] S2: Under zero-degree and nitrogen protection, the thiolate solution was added to the anhydrous ethanol solution of N,N-diethylchloroethylamine and reacted at 50-60°C for 48-72 h. The mixture was then quenched with water and the anhydrous ethanol was removed by vacuum distillation. The mixture was then subjected to the first post-treatment to obtain 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine.

[0051] S3: Under room temperature and nitrogen protection, anhydrous ethanol, potassium carbonate and sodium iodide were stirred until dissolved, and bromoethane and 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine were added sequentially. The temperature was gradually raised to a set temperature of 50-70°C and stirred for 12-48 hours. Water was added to quench the ethanol and anhydrous ethanol was removed by vacuum distillation. Then, a second post-treatment was performed to obtain 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine.

[0052] The ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine to anhydrous ethanol is 100g:2-5L.

[0053] In the specific implementation process, the first post-processing includes extraction, drying, vacuum distillation, and purification in sequence; specifically, the aqueous layer is extracted three times with dichloromethane. The organic phase is dried with anhydrous sodium carbonate, and dichloromethane is removed by vacuum distillation. The crude product is purified by silica gel chromatography (methanol:ethyl acetate = 1:3).

[0054] The second post-processing involved extraction, drying, vacuum distillation, and purification; specifically, the aqueous layer was extracted three times with dichloromethane. The organic phase was dried over anhydrous sodium carbonate and dichloromethane was removed by vacuum distillation. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3).

[0055] Specifically, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is prepared from sodium ethoxide, 3-amino-5-mercapto-1,2,4-triazole, N,N-diethylchloroethylamine, potassium carbonate, sodium iodide, and bromoethane.

[0056] The molar ratio of 3-amino-5-mercapto-1,2,4-triazole, sodium ethoxide, and N,N-diethylchloroethylamine is 1:(1.5-2):(1-1.2); 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazole-3-amine is prepared from sodium ethoxide, 3-amino-5-mercapto-1,2,4-triazole, and N,N-diethylchloroethylamine; the molar ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazole-3-amine, potassium carbonate, sodium iodide, and bromoethane is 1:(2-6):(1-2):1.

[0057] The detailed preparation process is as follows:

[0058] S1: Under nitrogen protection at room temperature, anhydrous ethanol and sodium ethoxide were added to the reactor and stirred until dissolved. 3-Amino-5-mercapto-1,2,4-triazole was slowly added, and the reaction was stirred for 1 h. Under nitrogen protection at 0 °C, the thiolate solution was added to an anhydrous ethanol solution of N,N-diethylchloroethylamine. The reaction was stirred at 50–60 °C for 48–72 h. The reaction was quenched with water, and anhydrous ethanol was removed by vacuum distillation. The aqueous layer was extracted three times with dichloromethane. The organic phase was dried over anhydrous sodium carbonate, and dichloromethane was removed by vacuum distillation. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazole-3-amine, in yield of 40%–60%. The molar ratio of 3-amino-5-mercapto-1,2,4-triazole:sodium ethoxide:N,N-diethylchloroethylamine is in the range of 1:1.5:1 to 1:2:1.2. For every 100g of 3-amino-5-mercapto-1,2,4-triazole, the corresponding solvent is 2-5L of anhydrous ethanol, 2-5L of water is used for quenching the reaction, and 2-5L of dichloromethane is used for extraction.

[0059] S2: Under nitrogen protection at room temperature, anhydrous ethanol, potassium carbonate, and sodium iodide were added to the reactor and stirred until dissolved. Bromoethane and the oily substance from the previous step, 5-((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, were added sequentially, and the temperature was gradually raised to 50–70 °C, stirred for 12–48 h. The mixture was quenched with water and anhydrous ethanol was removed by vacuum distillation. The aqueous layer was extracted three times with dichloromethane. The organic phase was dried over anhydrous sodium carbonate and dichloromethane was removed by vacuum distillation. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, with a yield of 40%–60%. The molar ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine:potassium carbonate:sodium iodide:bromoethane is in the range of 1:2:1:1 to 1:6:2:1. For every 100g of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, the corresponding solvent is 2-5L of anhydrous ethanol, 2-5L of water for quenching the reaction, and 2-5L of dichloromethane for extraction.

[0060] The fifth aspect of this invention provides an application of a phosphorus-free corrosion inhibitor in the pickling process of a power plant boiler. The phosphorus-free corrosion inhibitor is suitable for pickling media with a mass fraction of less than 10%. The pickling medium is any one of a mixture of glycolic acid and formic acid, citric acid, and EDTA, and the mass fraction of the phosphorus-free corrosion inhibitor added during the pickling process of the power plant boiler is 0.3% to 0.6%.

[0061] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0062] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0063] Example 1:

[0064] Example 1 of this application provides a method for preparing the main agent of a phosphorus-free corrosion inhibitor, the specific process of which is as follows:

[0065] 1) Under nitrogen protection at room temperature, anhydrous ethanol (2 L) was added to the reactor, followed by sodium ethoxide (97.8 g, 1.8 eq), and stirred with a mechanical stirrer until dissolved. 3-Amino-5-mercapto-1,2,4-triazole (100.0 g, 1.0 eq) was slowly added, and the reaction was allowed to proceed for 1 h. Subsequently, under nitrogen protection at 0 °C, the thiolate solution was added dropwise to a solution of N,N-diethylchloroethylamine (108.3 g, 1.0 eq) in anhydrous ethanol (2 L). The reaction was stirred at 60 °C for 48 h. Water (1 L) was added, and the anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, in 55% yield.

[0066] 2) Under nitrogen protection at room temperature, potassium carbonate (552.0 g, 4.0 eq) and sodium iodide (148.9 g, 1.0 eq) were added to the reactor and stirred with a mechanical stirrer until dissolved. Then, bromoethane (109.0 g, 1.0 eq) and the oily substance from the previous step, 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine (215.2 g, 1.0 eq), were added. The temperature was then gradually increased to 70 °C and stirred for 24 h. Water (1 L) was added and anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane (2.5 L). The combined organic layers were dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 5-((2-(diethylamino)ethyl)thio)-N,N-diethyl-4H-1,2,4-triazol-3-amine.

[0067] Example 1 of this application also provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0068] Under stirring, the demineralized water is heated to 50°C. First, 2.0% by mass of dodecyl dimethyl betaine is added and dissolved. Then, 1.5% L-methionine and 0.5% benzotriazole are added. Subsequently, 4.0% ethylene glycol is added and stirred evenly. Then, 4.0% of the main agent is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor suitable for acid washing of power plant boilers.

[0069] According to DL / T 523-2017 "Evaluation Index and Test Method of Application Performance of Chemical Cleaning Corrosion Inhibitors", the corrosion inhibitor prepared by this method was used to conduct a dynamic cleaning evaluation experiment. The cleaning medium was 4% glycolic acid + formic acid, with 0.3% of the corrosion inhibitor prepared by the method in Example 1 added. The cleaning temperature was 95℃, the circulation cleaning time was 24h, and the flow rate was 1.0m / s. The test results are shown in Table 1.

[0070] Table 1. Results of corrosion rate assessment test in chemical cleaning in Example 1

[0071]

[0072] The test results show that the corrosion rates of various materials all meet the excellent standards specified in DL / T 794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants", verifying the good corrosion inhibition performance of the phosphorus-free corrosion inhibitor.

[0073] Example 2:

[0074] Example 2 of this application provides a method for preparing the main agent for a phosphorus-free corrosion inhibitor, the specific process of which is as follows:

[0075] 1) Under nitrogen protection at room temperature, anhydrous ethanol (2 L) was added to the reactor, followed by sodium ethoxide (108.6 g, 2.0 eq), and stirred with a mechanical stirrer until dissolved. 3-Amino-5-mercapto-1,2,4-triazole (100.0 g, 1.0 eq) was slowly added, and the reaction was allowed to proceed for 1 h. Subsequently, under nitrogen protection at 0 °C, the thiolate solution was added dropwise to a solution of N,N-diethylchloroethylamine (108.3 g, 1.0 eq) in anhydrous ethanol (3 L). The reaction was stirred at 55 °C for 48 h. Water (1 L) was added, and the anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, in 54% yield.

[0076] 2) Under nitrogen protection at room temperature, potassium carbonate (552.0 g, 4.0 eq) and sodium iodide (148.9 g, 1.0 eq) were added to the reactor and stirred with a mechanical stirrer until dissolved. Then, bromoethane (109.0 g, 1.0 eq) and the oily substance from the previous step, 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine (215.2 g, 1.0 eq), were added. The temperature was then gradually increased to 70 °C and stirred for 24 h. Water (1 L) was added and anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane (2.5 L). The combined organic layers were dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 5-((2-(diethylamino)ethyl)thio)-N,N-diethyl-4H-1,2,4-triazol-3-amine.

[0077] Example 2 of this application also provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0078] Under stirring, the demineralized water is heated to 50°C. First, 1.5% by mass of dodecyl dimethyl betaine is added and dissolved. Then, 1.8% L-methionine and 0.5% benzotriazole are added. Subsequently, 4.0% ethylene glycol is added and stirred evenly. Then, 4.0% of the main agent is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor suitable for acid washing of power plant boilers.

[0079] According to DL / T 523-2017 "Evaluation Indexes and Test Methods for Application Performance of Chemical Cleaning Corrosion Inhibitors", the corrosion inhibitor prepared by this method was used to conduct a dynamic cleaning evaluation experiment. The cleaning medium was 6% ethylenediaminetetraacetic acid, with the addition of 0.3% hexamethylenetetraacetic acid, 0.03% MBT, and hydrazine at 1500 mg / L. The cleaning temperature was 95℃. 0.3% of the corrosion inhibitor prepared by the method in Example 2 was added. The cleaning temperature was 95℃, the circulation cleaning time was 24 h, and the flow rate was 1.0 m / s. The test pieces were mainly made of SA-210C and 15CrMoG. The test results are shown in Table 2.

[0080] After chemical cleaning, the corrosion rate of the test piece was measured, and the results are shown in Table 2. It can be seen that the corrosion rate measured by the corrosion indicator piece meets the standard specified in DL / T 794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants".

[0081] Table 2 Corrosion rate of corrosion indicator during chemical cleaning in Example 2

[0082]

[0083] Example 3:

[0084] Example 3 of this application provides a method for preparing the main agent of a phosphorus-free corrosion inhibitor, the specific process of which is as follows:

[0085] 1) Under nitrogen protection at room temperature, anhydrous ethanol (1 L) was added to the reactor, followed by sodium ethoxide (108.6 g, 2.0 eq), and stirred with a mechanical stirrer until dissolved. 3-Amino-5-mercapto-1,2,4-triazole (100.0 g, 1.0 eq) was slowly added, and the reaction was allowed to proceed for 1 h. Subsequently, under nitrogen protection at 0 °C, the thiolate solution was added dropwise to a solution of N,N-diethylchloroethylamine (108.3 g, 1.0 eq) in anhydrous ethanol (1 L). The reaction was stirred at 55 °C for 48 h. Water (1 L) was added, and the anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, in 57% yield.

[0086] 2) Under nitrogen protection at room temperature, potassium carbonate (552.0 g, 4.0 eq) and sodium iodide (148.9 g, 1.0 eq) were added to the reactor and stirred with a mechanical stirrer until dissolved. Then, bromoethane (109.0 g, 1.0 eq) and the oily substance from the previous step, 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine (215.2 g, 1.0 eq), were added. The temperature was then gradually increased to 70 °C and stirred for 24 h. Water (1 L) was added and anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane (2.5 L). The combined organic layers were dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 5-((2-(diethylamino)ethyl)thio)-N,N-diethyl-4H-1,2,4-triazol-3-amine.

[0087] Example 3 of this application also provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0088] Under stirring, the demineralized water is heated to 50°C. First, 2.0% dodecyl dimethyl betaine is added and dissolved. Then, 2.0% L-methionine and 0.5% benzotriazole are added. Subsequently, 3.0% ethylene glycol is added and stirred evenly. Then, 12.0% of the main agent is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor suitable for acid washing of power plant boilers.

[0089] According to DL / T 523-2017 "Evaluation Index and Test Method of Application Performance of Chemical Cleaning Corrosion Inhibitors", a dynamic cleaning evaluation experiment was conducted on the corrosion inhibitor prepared by this method. In all three cleaning stages, 8% citric acid was used as the pickling medium, 0.5% of the phosphorus-free corrosion inhibitor prepared by the method in Example 3 was added, and 0.05% of the co-solvent was added. The cleaning temperature was 95℃, the circulation cleaning time was 24h, and the flow rate was 1.0m / s. The test pieces were mainly made of T91, T23, TP347H, and S304.

[0090] After chemical cleaning, the corrosion rate of the test piece was measured, and the results are shown in Table 3. It can be seen that the corrosion rate measured by the corrosion indicator piece meets the standard specified in DL / T 794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants".

[0091] Table 3 Corrosion rate of corrosion indicator during chemical cleaning in Example 3

[0092]

[0093]

[0094] Example 4:

[0095] Example 4 of this application provides a method for preparing the main agent for a phosphorus-free corrosion inhibitor, the specific process of which is as follows:

[0096] 1) Under nitrogen protection at room temperature, anhydrous ethanol (1 L) was added to the reactor, followed by sodium ethoxide (81.5 g, 1.5 eq), and stirred with a mechanical stirrer until dissolved. 3-Amino-5-mercapto-1,2,4-triazole (100.0 g, 1.0 eq) was slowly added, and the reaction was allowed to proceed for 1 h. Subsequently, under nitrogen protection at 0 °C, the thiolate solution was added dropwise to an anhydrous ethanol solution (1 L) of N,N-diethylchloroethylamine (108.3 g, 1.0 eq). The reaction was stirred at 50 °C for 48 h. Water (1 L) was added, and the anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, in 53% yield.

[0097] 2) Under nitrogen protection at room temperature, potassium carbonate (276.0 g, 2.0 eq) and sodium iodide (148.9 g, 1.0 eq) were added to the reactor and stirred with a mechanical stirrer until dissolved. Then, bromoethane (109.0 g, 1.0 eq) and the oily substance from the previous step, 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine (215.2 g, 1.0 eq), were added. The temperature was then gradually increased to 50 °C and stirred for 12 h. Water (1 L) was added and anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane (2.5 L). The combined organic layers were dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 5-((2-(diethylamino)ethyl)thio)-N,N-diethyl-4H-1,2,4-triazol-3-amine.

[0098] Example 4 of this application also provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0099] Under stirring, the demineralized water is heated to 50°C. First, 0.3% dodecyl dimethyl betaine is added and dissolved. Then, 1.0% L-methionine and 0.5% benzotriazole are added, followed by 3.0% ethylene glycol. After stirring evenly, 2.0% of the main agent is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor suitable for acid washing of power plant boilers.

[0100] According to DL / T 523-2017 "Evaluation Index and Test Method of Application Performance of Chemical Cleaning Corrosion Inhibitors", a dynamic cleaning evaluation experiment was conducted on the corrosion inhibitor prepared by this method. In all three cleaning stages, 8% citric acid was used as the pickling medium, 0.6% of the phosphorus-free corrosion inhibitor prepared by the method in Example 4 was added, and 0.05% of the co-solvent was added. The cleaning temperature was 95℃, the circulation cleaning time was 24h, the flow rate was 1.0m / s, and the test pieces were mainly made of T91 and T23 materials.

[0101] After chemical cleaning, the corrosion rate of the test piece was measured, and the results are shown in Table 4. It can be seen that the corrosion rate measured by the corrosion indicator piece meets the standard specified in DL / T 794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants".

[0102] Table 4 Corrosion rate of corrosion indicator during chemical cleaning in Example 4

[0103]

[0104] Example 5:

[0105] Example 5 of this application provides a method for preparing the main agent of a phosphorus-free corrosion inhibitor, the specific process of which is as follows:

[0106] 1) Under nitrogen protection at room temperature, anhydrous ethanol (3 L) was added to the reactor, followed by sodium ethoxide (108.6 g, 2.0 eq), and stirred with a mechanical stirrer until dissolved. 3-Amino-5-mercapto-1,2,4-triazole (100.0 g, 1.0 eq) was slowly added, and the reaction was allowed to proceed for 1 h. Subsequently, under nitrogen protection at 0 °C, the thiolate solution was added dropwise to a solution of N,N-diethylchloroethylamine (130.0 g, 1.2 eq) in anhydrous ethanol (2 L). The reaction was stirred at 60 °C for 72 h. Water (1 L) was added, and the anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane. The combined organic layers were dried over anhydrous magnesium sulfate, and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 1:3) to give an oily compound 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, in 61% yield.

[0107] 2) Under nitrogen protection at room temperature, potassium carbonate (828.0 g, 6.0 eq) and sodium iodide (297.8 g, 2.0 eq) were added to the reactor and stirred with a mechanical stirrer until dissolved. Then, bromoethane (109.0 g, 1.0 eq) and the oily substance from the previous step, 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine (215.2 g, 1.0 eq), were added. The temperature was then gradually increased to 70 °C and stirred for 48 h. Water (3 L) was added and anhydrous ethanol was removed under reduced pressure. The aqueous layer was extracted three times with dichloromethane (2.5 L). The combined organic layers were dried over anhydrous magnesium sulfate and the solvent was removed by distillation under reduced pressure. The crude product was purified by silica gel chromatography (methanol:ethyl acetate = 2:3) to obtain the main agent, whose main component is 5-((2-(diethylamino)ethyl)thio)-N,N-diethyl-4H-1,2,4-triazol-3-amine.

[0108] Example 5 of this application also provides a method for preparing a phosphorus-free corrosion inhibitor, comprising the following steps:

[0109] Under stirring, the demineralized water is heated to 70°C. First, 2.0% dodecyl dimethyl betaine is added and dissolved. Then, 2.0% L-methionine and 1.0% benzotriazole are added, followed by 5.0% ethylene glycol. After stirring evenly, 12.0% of the main agent is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor suitable for acid washing of power plant boilers.

[0110] According to DL / T 523-2017 "Evaluation Index and Test Method of Application Performance of Chemical Cleaning Corrosion Inhibitors", a dynamic cleaning evaluation experiment was conducted on the corrosion inhibitor prepared by this method. In all three cleaning stages, 10% citric acid was used as the pickling medium, 0.3% of the phosphorus-free corrosion inhibitor prepared by the method in Example 5 was added, and 0.05% of the co-solvent was added. The cleaning temperature was 95℃, the circulation cleaning time was 24h, the flow rate was 1.0m / s, and the test pieces were mainly made of T91 and T23 materials.

[0111] After chemical cleaning, the corrosion rate of the test piece was measured, and the results are shown in Table 5. It can be seen that the corrosion rate measured by the corrosion indicator piece meets the standard specified in DL / T 794-2012 "Guidelines for Chemical Cleaning of Boilers in Thermal Power Plants".

[0112] Table 5. Corrosion rate of the corrosion indicator during chemical cleaning in Example 5.

[0113]

[0114] In summary, the phosphorus-free corrosion inhibitor provided by this invention exhibits excellent corrosion inhibition performance and is not easily decomposed under acid pickling conditions or at high temperatures. Furthermore, the phosphorus-free corrosion inhibitor has low biotoxicity during wastewater treatment and causes minimal environmental pollution.

[0115] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A main agent, characterized in that, The main agent is 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine; The structural formula of the 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is as follows:

2. An application of the main agent according to claim 1, characterized in that, The application of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazole-5-amine in the preparation of phosphorus-free corrosion inhibitors.

3. A phosphorus-free corrosion inhibitor, characterized in that, Based on the main agent described in claim 1, the raw materials of the phosphorus-free corrosion inhibitor, by mass percentage, include 2.0% to 12.0% of 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine, 1.0% to 2.0% of L-methionine, 0.5% to 1.0% of benzotriazole, 0.3% to 2.0% of dodecyl dimethyl betaine, and 3.0% to 5.0% of ethylene glycol, with the balance being demineralized water.

4. A method for preparing the phosphorus-free corrosion inhibitor according to claim 3, characterized in that, Includes the following steps: The deionized water is heated to 50-70°C. Dodecyl dimethyl betaine is added while stirring. After it dissolves, L-methionine and benzotriazole are added, followed by ethylene glycol. After stirring evenly, 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is added and mixed evenly to obtain a phosphorus-free corrosion inhibitor.

5. The method for preparing the phosphorus-free corrosion inhibitor according to claim 4, characterized in that, The preparation process of the 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine is as follows: Under nitrogen protection at room temperature, anhydrous ethanol and sodium ethoxide were stirred until dissolved, and 3-amino-5-mercapto-1,2,4-triazole was slowly added while stirring to obtain a thiolate solution. Under zero-degree and nitrogen protection, the thiolate solution was added to the anhydrous ethanol solution of N,N-diethylchloroethylamine to carry out the reaction. The reaction was quenched with water and the anhydrous ethanol was removed by vacuum distillation. Then, the reaction was carried out by extraction, drying, vacuum distillation and purification to obtain 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine. Under nitrogen protection at room temperature, anhydrous ethanol, potassium carbonate, and sodium iodide were stirred until dissolved, and then bromoethane and 5-((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine were added sequentially. The mixture was gradually heated to the set temperature with stirring, quenched with water, and the anhydrous ethanol was removed by vacuum distillation. The mixture was then subjected to extraction, drying, vacuum distillation, and purification to obtain 3-((2-(diethylamino)ethyl)thio)-1-ethyl-1H-1,2,4-triazol-5-amine.

6. The method for preparing the phosphorus-free corrosion inhibitor according to claim 5, characterized in that, The molar ratio of 3-amino-5-mercapto-1,2,4-triazole, sodium ethoxide, and N,N-diethylchloroethylamine is 1:(1.5-2):(1-1.2).

7. The method for preparing the phosphorus-free corrosion inhibitor according to claim 5, characterized in that, The molar ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazol-3-amine, potassium carbonate, sodium iodide, and bromoethane is 1:(2-6):(1-2):

1.

8. The method for preparing the phosphorus-free corrosion inhibitor according to claim 5, characterized in that, The ratio of 3-amino-5-mercapto-1,2,4-triazole to anhydrous ethanol is 100g:2-5L; the ratio of 5((2-(diethylamino)ethyl)thio)-4H-1,2,4-triazole-3-amine to anhydrous ethanol is 100g:2-5L; the reaction temperature of the thiolate solution and the anhydrous ethanol solution of N,N-diethylchloroethylamine is 50-60℃, and the reaction stirring time is 48-72h; the set temperature is 50-70℃, and the stirring time is 12-48h.

9. The application of the phosphorus-free corrosion inhibitor according to claim 3 in the acid washing process of power plant boilers.

10. The application of the phosphorus-free corrosion inhibitor according to claim 9, characterized in that, The phosphorus-free corrosion inhibitor is suitable for pickling media with a mass fraction of less than 10%; the pickling media is any one of a mixture of glycolic acid and formic acid, citric acid and EDTA; the phosphorus-free corrosion inhibitor is added at a mass fraction of 0.3% to 0.6% during the pickling process of power plant boilers.

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