A carbon steel acid corrosion inhibitor, its preparation method and application

Abstract

This invention discloses an acid corrosion inhibitor for carbon steel, its preparation method, and its application, belonging to the field of chemical corrosion protection technology. The invention uses Mannich base as the main agent and sulfur-containing polyamino acids as synergists, mixed with a solvent. Addressing the technical problems of existing acid corrosion inhibitors, such as increased costs due to high concentrations, and the presence of hazardous chemicals, costly surfactants, and foaming components in their formulations, this invention uses a small-molecule Mannich base and a long-chain sulfur-containing polyamino acid to construct a structure with multiple adsorption sites (N, O, and benzene ring adsorption sites on the Mannich base molecule and S, N, and O adsorption sites on the sulfur-containing polyamino acid molecular chain) and strong adsorption capacity (S has strong electronegativity). This allows for the formation of a robust and stable corrosion inhibitor adsorption film in high-temperature, strongly acidic environments, achieving excellent slow-release effects without pitting corrosion.

Description

Technical Field

[0001] This invention relates to the field of chemical corrosion protection technology, specifically to an acid corrosion inhibitor for carbon steel, its preparation method, and its application. Background Technology

[0002] Acid fracturing and acid plugging are common oilfield production enhancement methods. While increasing oil and gas production, the coupling effect of the extremely low pH value of the acid solution and the high temperature conditions can cause severe corrosion to metal tubing. This not only affects the service safety of the tubing but also increases development costs. Corrosion inhibitors are typically added to the acid system to reduce its corrosiveness and protect the tubing. However, due to the extremely low pH value and strong corrosiveness of the acid system, conventional acid fracturing corrosion inhibitors are mostly small molecules with few adsorption sites and are prone to desorption under high temperature conditions, leading to pitting corrosion. To achieve a good corrosion inhibition effect, a high concentration of corrosion inhibitor is required, resulting in high costs.

[0003] Commonly used acid corrosion inhibitors mainly include quinoline quaternary ammonium salts, pyridine quaternary ammonium salts, and aldehyde-ketone-amine condensates. For example, patent application CN119192072A discloses a high-temperature acid corrosion inhibitor for oilfields, its preparation method, and its application. This inhibitor uses (S)-1-amino-3-chloro-2-propanol hydrochloride, aldehyde compounds such as terephthalaldehyde, succinic anhydride, and quinoline as raw materials, and prepares a novel high-temperature acid corrosion inhibitor for oilfields through Schiff base, anhydride esterification, and quaternization reactions. In a 20% HCl medium, adding 3 wt% of this inhibitor can achieve a corrosion inhibition rate of over 75% for N80 materials. However, this formulation requires a 3 wt% concentration of the inhibitor, resulting in a relatively high cost.

[0004] The invention patent application with publication number CN118755468A discloses an acidizing corrosion inhibitor for fracturing oil and gas wells and its preparation method. It is prepared by using o-methoxybenzaldehyde modified meso-tetramethyl-meso-tetra-p-aminophenylcalix[4]pyrrole, amphoteric organic ionic salt, diazolidinyl urea, hydroxypropyltrimethylammonium chloride chitosan, bis(2-hydroxyethyl)amino(trihydroxymethyl)methane, lauryl hydroxyethyl imidazoline, hexamethylenetetramine, nonionic fluorocarbon surfactant, dodecyltrimethylammonium chloride, APG1214 surfactant, cosolvent and water. At 90℃ and 20% HCl, when the amount of corrosion inhibitor added is 1wt%, the corrosion rate of N80 is about 0.4[g / (m·h)]~1.2[g / (m·h)]. This formulation has a complex composition, making industrialization inconvenient. Furthermore, the nonionic fluorocarbon surfactant used is expensive, and hexamethylenetetramine is listed as a potentially explosive hazardous chemical, unsuitable for industrial application. The formulation also uses a large amount of surfactant, and imidazoline itself has foaming properties, leading to a high tendency for the formulation to foam. Additionally, since 2025, oil fields have banned the use of chemicals containing organochlorine. Summary of the Invention

[0005] This invention provides a carbon steel acid corrosion inhibitor, its preparation method, and its application, effectively solving the technical problems of increased costs due to high concentrations of existing acid corrosion inhibitors, and the presence of hazardous chemicals, costly surfactants, and foaming components in the formulation of existing acid corrosion inhibitors.

[0006] This invention uses Mannich base as the main agent and sulfur-containing polyamino acids as synergists mixed with solvent to obtain a carbon steel acidizing corrosion inhibitor. By constructing multiple adsorption sites and introducing heteroatoms S, N, and O with strong adsorption properties into the molecular structure design, the film-forming ability and film strength of the corrosion inhibitor are enhanced, and the concentration of the corrosion inhibitor added is reduced. This provides a high-efficiency, economical, non-foaming, and organochlorine-free carbon steel acidizing corrosion inhibitor, which is of great significance for the safety of oilfield acidizing fracturing operations, cost reduction and efficiency improvement, and protection of the service safety of tubing strings.

[0007] The first objective of this invention is to provide a carbon steel acid corrosion inhibitor, wherein the carbon steel acid corrosion inhibitor is composed of Mannich base as the main agent, sulfur-containing polyamino acid as the synergist, and a solvent.

[0008] The Mannich base is .

[0009] The sulfur-containing polyamino acid is Where m is 10~30 and n is 6~50.

[0010] The mass ratio of the Mannich base, sulfur-containing polyamino acid, and solvent is 1~3:1:2.5~7.

[0011] For the sulfur-containing polyamino acids used in this invention, when the m and n values ​​in their structural formula are relatively small, the molecular weight is small, the chain length is short, and the multi-point adsorption on the metal surface is insufficient, resulting in weak adsorption bonds. In high-temperature, highly corrosive media, they are prone to desorption, making it difficult to form a dense and complete coating layer, leading to defects. The corrosive medium can still penetrate and contact the matrix, resulting in low corrosion inhibition efficiency. Conversely, when the m and n values ​​are relatively large, the excessively high molecular weight leads to reduced polymer solubility in the medium, causing entanglement, aggregation, or even precipitation, preventing uniform dispersion and reducing corrosion inhibition. The sulfur-containing polyamino acids used in this invention have a structural formula where m is limited to 10-30 and n to 6-50, achieving optimal corrosion inhibition effects.

[0012] In a preferred embodiment, the solvent is N,N-dimethylformamide, tetrahydrofuran, N,N-dimethylacetamide, or ethylene glycol monobutyl ether.

[0013] In a preferred embodiment, the Mannich base is prepared by reacting benzamide, aniline, and formaldehyde in an alcohol solvent at a molar ratio of 1:1:1.2~2, heated to 60℃~80℃ for 6h~12h. The alcohol solvent is ethanol.

[0014] A second objective of this invention is to provide a method for preparing the carbon steel acid corrosion inhibitor described in any of the above claims, comprising the following steps: Using Mannich base as the main agent, a primary corrosion inhibitor is formed by mixing it with a solvent. The primary corrosion inhibitor is then mixed with sulfur-containing polyamino acids to obtain a carbon steel acidification corrosion inhibitor.

[0015] The third objective of this invention is to provide an application of the carbon steel acid corrosion inhibitor described in any one of the above claims in carbon steel corrosion prevention. The application method is as follows: the carbon steel acid corrosion inhibitor is added to an acid solution to form an anti-corrosion solution, and the carbon steel is immersed in the anti-corrosion solution for carbon steel corrosion prevention.

[0016] In a preferred embodiment, the amount of carbon steel acid corrosion inhibitor added to the acid solution is 0.5wt%~1wt%.

[0017] In a preferred embodiment, the mass concentration of the acid solution is 15% to 20%.

[0018] In a preferred embodiment, the acid solution is hydrochloric acid.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a carbon steel acid corrosion inhibitor, which is composed of Mannich base as the main agent, sulfur-containing polyamino acid as the synergist, and mixed with a solvent.

[0020] Given the increased cost due to the high concentration of existing acid corrosion inhibitors, and the technical problems associated with the formulation of acid corrosion inhibitors including hazardous chemicals, costly surfactants, and easily foaming components, this invention addresses these issues by combining small-molecule Mannich bases with long-chain sulfur-containing polyamino acids. This results in a structure with multiple adsorption sites (N, O, and benzene ring adsorption sites on the Mannich base molecule and S, N, and O adsorption sites on the sulfur-containing polyamino acid molecule chain) and strong adsorption capacity (S has strong electronegativity). This structure can form a robust and stable corrosion inhibitor adsorption film in high-temperature, strongly acidic environments, achieving excellent slow-release effects without pitting corrosion.

[0021] This invention uses a small-molecule Mannich base combined with polyamino acids. Compared with other conventional small-molecule acid corrosion inhibitors, it has more adsorption sites and longer molecular chains, which can spread and adsorb over a larger area, thereby forming a dense adsorption film. This reduces the concentration of the additive and significantly lowers the cost of the acid corrosion inhibitor, thus reducing the cost of acidification and production enhancement operations.

[0022] This invention contains no surfactants, so there is no foaming problem, and it does not contain organochlorine, which meets the requirements of oil fields to be free of organochlorine. Attached Figure Description

[0023] Figure 1 This is a comparison chart showing the corrosion inhibition effect of the acid corrosion inhibitors used in the embodiments and comparative examples of this invention on carbon steel.

[0024] Figure 2 The image shows the macroscopic corrosion morphology of N80 material after film removal in 15% HCl at 90°C without using the acid corrosion inhibitor of the present invention.

[0025] Figure 3 The image shows the macroscopic corrosion morphology of N80 material after film removal in 20% HCl at 90°C without using the acid corrosion inhibitor of the present invention.

[0026] Figure 4 Macroscopic corrosion morphology of N80 material after film removal in 20% HCl when using the carbon steel acid corrosion inhibitor of Example 1 of the present invention.

[0027] Figure 5 The image shows the macroscopic corrosion morphology of N80 material after film removal in 15% HCl when using the carbon steel acid corrosion inhibitor of Example 6 of this invention.

[0028] Figure 6 The image shows the macroscopic corrosion morphology of N80 material after film removal in 20% HCl when using the acid corrosion inhibitor of Comparative Example 1 of this invention.

[0029] Figure 7 The image shows the macroscopic corrosion morphology of N80 material after film removal in 20% HCl when using the acid corrosion inhibitor of Comparative Example 2 of this invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0031] The technical solution of the present invention will be analyzed and explained below.

[0032] This invention provides a carbon steel acid corrosion inhibitor, which is composed of Mannich base as the main agent, sulfur-containing polyamino acid as the synergist, and a solvent.

[0033] The Mannich base is .

[0034] The sulfur-containing polyamino acid is Where m is 10~30 and n is 6~50.

[0035] The mass ratio of the Mannich base, sulfur-containing polyamino acid, and solvent is 1~3:1:2.5~7.

[0036] In the above technical solution, the present invention uses Mannich base and sulfur-containing polyamino acid compound. In an acidic medium, Mannich base can react with Fe ions on the surface of a metal matrix (carbon steel) to form a chelate with a five-membered ring structure. The polymer and benzene rings are adsorbed onto the iron substrate surface, while the long chains of the polyamino acid spread and adsorb onto the metal substrate surface, forming a film through interweaving. Small-molecule Mannich bases can fill weak points in the film. The high electronegativity of the heteroatoms (S) in the sulfur-containing polyamino acid enhances the film's robustness. This invention overcomes the problems of poor adsorption performance, easy desorption at high temperatures, and pitting corrosion in conventional small-molecule acid corrosion inhibitors under high temperature and low pH conditions. Compared with conventional small-molecule acid corrosion inhibitors, the inhibitor of this invention has multiple adsorption sites, and the polymer and small molecules interweave to form a dense and robust film, reducing the risk of uniform corrosion and pitting corrosion. Simultaneously, reducing the amount of inhibitor added effectively lowers the corrosion protection cost of the acidification system, achieving the goal of cost reduction and efficiency improvement.

[0037] The technical effects of the present invention will be described below through specific embodiments and comparative examples.

[0038] The sulfur-containing polyamino acid used in this invention is: Where m = 10~30, n = 6~50.

[0039] The method for preparing sulfur-containing polyamino acids used in this invention is described in existing literature, namely: Deng, Y.; Chen, H.; Tao, X.; Cao, F.; Trépout, S.; Ling, J.; Li, M.-H. Oxidation-Sensitive Polymersomes Based on Amphiphilic Diblock Copolypeptoids. Biomacromolecules 2019, 20(9), 3435-3444.

[0040] The preparation method of the above-mentioned sulfur-containing polyamino acids includes the following steps: Step 1: Mix 3-(methylthio)-1-propylamine hydrochloride and glyoxylic acid aqueous solution with 2 mol / L HCl, then react the mixture at 100℃ under reflux for 10-14 h. After removing the solvent by evaporation and purifying with acetone, N-3-(methylthio)propylglycine hydrochloride of Formula I is obtained. The molar ratio of 3-(methylthio)-1-propylamine hydrochloride to acetaldehyde is 1:2.0-2.5. The above synthetic route is as follows:

[0041] .

[0042] Step 2: Dissolve NaOH in 400 mL of water, add N-3-(methylthio)propylglycine hydrochloride of Formula I and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II with stirring. After reacting for 48-72 h, add 30-60 mL of concentrated hydrochloric acid (analytical grade, purchased from Sinopharm Chemical Reagent Co., Ltd.) with a mass concentration of 36%-38% for acidification, wash, dry, concentrate under reduced pressure, add PBr3 dropwise with stirring, and cool in an ice bath to obtain compound of Formula III. The molar ratio of NaOH, N-3-(methylthio)propylglycine hydrochloride of Formula I, and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II is 2.0-2.5:1:1; the molar ratio of N-3-(methylthio)propylglycine hydrochloride of Formula I to PBr3 is 1:0.1-0.3. The above synthetic route is as follows:

[0043] .

[0044] Step 3: Dissolve NaOH in 400 mL of water, add sarcosine and S-ethoxythiocarbonyl mercaptoacetic acid of formula II with stirring, react for 48-72 h, then add 30-60 mL of concentrated hydrochloric acid (36%-38% by mass) for acidification, wash, dry, concentrate under reduced pressure, then dissolve the product in dry chloroform, add PBr3 dropwise with stirring, and cool in an ice bath. After the reaction is complete, cool and stir for 10-30 min, wash, dry, concentrate under reduced pressure, and vacuum distill to obtain compound of formula IV. The molar ratio of NaOH, sarcosine, and S-ethoxythiocarbonyl mercaptoacetic acid of formula II is 2.0-2.5:1:1; the molar ratio of S-ethoxythiocarbonyl mercaptoacetic acid of formula II to PBr3 is 1:0.1-0.3. The above synthetic route is as follows:

[0045] .

[0046] Step 4: Dissolve the compound of formula III in anhydrous THF, add benzylamine solution, react at 50℃~70℃ for 36h~72h, add the compound of formula IV, and continue reacting at 50℃~70℃ for 30h~40h. Then, purify by precipitation with diethyl ether, and dry under vacuum to obtain the compound of formula V, i.e., the sulfur-containing polyamino acid; wherein the molar ratio of the compound of formula III to the compound of formula IV is 1:0.3~5; the above reaction synthesis route is as follows: .

[0047] Example 1 A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Preparation of Mannich base: Benzamide was dissolved in ethanol, and aniline and formaldehyde were added in a molar ratio of 1:1:1.2. The mixture was reacted at 75°C for 9 hours. After removing the solvent by vacuum distillation, solid Mannich base was obtained.

[0048] S2, Preparation of sulfur-containing polyamino acids: 3-(methylthio)-1-propylamine hydrochloride and glyoxylic acid aqueous solution with a molar ratio of 1:2 were mixed with HCl with a concentration of 2 mol / L. The mixture was then reacted at a reflux temperature of 100℃ for 10 h. The solvent was removed by evaporation and purified with acetone to obtain N-3-(methylthio)propylglycine hydrochloride of formula I.

[0049] NaOH was dissolved in 400 mL of water, and N-3-(methylthio)propylglycine hydrochloride of Formula I and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II were added with stirring. After reacting for 48 h, 30 mL of concentrated hydrochloric acid with a mass concentration of 36%~38% was added for acidification, followed by washing, drying, and concentration under reduced pressure. 0.3 mol of PBr3 was added dropwise with stirring, and the mixture was cooled in an ice bath to obtain compound of Formula III. The molar ratio of NaOH, N-3-(methylthio)propylglycine hydrochloride of Formula I, and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II was 2:1:1.

[0050] NaOH was dissolved in 400 mL of water. While stirring, sarcosine and S-ethoxythiocarbonyl mercaptoacetic acid of formula II were added. After reacting for 72 h, 30 mL of concentrated hydrochloric acid (36%–38% by mass) was added for acidification. The mixture was washed, dried, and concentrated under reduced pressure. The product was then dissolved in 350 mL of dry chloroform. 0.3 mol of PBr3 was added dropwise while stirring. The mixture was cooled in an ice bath. After the reaction was complete, the mixture was cooled and stirred for 30 min. The mixture was then washed, dried, concentrated under reduced pressure, and vacuum distilled to obtain the compound of formula IV. The molar ratio of NaOH, sarcosine, and S-ethoxythiocarbonyl mercaptoacetic acid of formula II was 2.5:1:1.

[0051] 0.3 g of compound III was dissolved in 3.0 mL of anhydrous THF, and 2.14 mg of 0.08 M benzylamine solution was added. The mixture was reacted in an oil bath at 50 °C for 36 h. Then, compound IV was added at a molar ratio of 1:0.3 (compound III to compound IV), and the reaction was continued for another 30 h. The mixture was then purified by precipitation with diethyl ether and dried under vacuum to obtain compound V, which is a sulfur-containing polyamino acid with the following structural formula: .

[0052] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 0.7wt%.

[0053] Example 2 Compared with Example 1, the differences are as follows: when preparing Mannich base, the molar ratio of benzamide, aniline and formaldehyde is 1:1:1.5, and the reaction is carried out at 80°C for 6 hours; when preparing carbon steel acid corrosion inhibitor, tetrahydrofuran is used as the solvent.

[0054] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Preparation of Mannich base: Benzamide was dissolved in ethanol, and aniline and formaldehyde were added in a molar ratio of 1:1:1.5. The mixture was heated to 80°C and reacted for 6 hours. After removing the solvent by vacuum distillation, solid Mannich base was obtained.

[0055] S2, sulfur-containing polyamino acid, is the same as in Example 1.

[0056] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of tetrahydrofuran, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H2. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0057] Example 3 The difference compared to Example 1 is that the molar ratio of benzamide, aniline and formaldehyde is 1:1:2 when preparing the Mannich base, and N,N-dimethylacetamide is used as the solvent.

[0058] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Preparation of Mannich base: Benzamide was dissolved in ethanol, and aniline and formaldehyde were added in a molar ratio of 1:1:2. The mixture was heated to 75°C and reacted for 9 hours. After removing the solvent by vacuum distillation, solid Mannich base was obtained.

[0059] S2, sulfur-containing polyamino acid, is the same as in Example 1.

[0060] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylacetamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H3. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0061] Example 4 Compared with Example 3, the differences are as follows: when preparing the Mannich base, the reaction was carried out at 60°C for 12 hours; and when preparing the carbon steel acid corrosion inhibitor, ethylene glycol monobutyl ether was used as the solvent.

[0062] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Preparation of Mannich base: Benzamide was dissolved in ethanol, and aniline and formaldehyde were added in a molar ratio of 1:1:2. The mixture was heated to 60°C and reacted for 12 hours. After removing the solvent by vacuum distillation, solid Mannich base was obtained.

[0063] S2, sulfur-containing polyamino acid, is the same as in Example 1.

[0064] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of ethylene glycol monobutyl ether, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H4. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0065] Example 5 The difference compared to Example 1 is that the amount of corrosion inhibitor added in the corrosion test is 0.5 wt%.

[0066] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0067] S2, sulfur-containing polyamino acid, same as in Example 1 S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 0.5wt%.

[0068] Example 6 The difference compared to Example 1 is that the amount of corrosion inhibitor added in the corrosion test is 1.0 wt%.

[0069] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0070] S2, sulfur-containing polyamino acid, same as in Example 1 S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 1.0wt%.

[0071] Example 7 Compared with Example 1, the difference is that the amounts of Mannich base, sulfur-containing polyamino acid and N,N-dimethylformamide added are 20g, 10g and 70g respectively, and the corrosion inhibitor is designated as H5.

[0072] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0073] S2, sulfur-containing polyamino acid, same as in Example 1 S3: Weigh 20g of the Mannich base prepared by S1 and dissolve it in 70g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 10g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H5. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0074] Example 8 The difference from Example 1 is that the amounts of Mannich base, sulfur-containing polyamino acid and N,N-dimethylformamide added are 20g, 20g and 60g respectively, and the corrosion inhibitor is designated as H6.

[0075] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0076] S2, sulfur-containing polyamino acid, same as in Example 1 S3: Weigh 20g of the Mannich base prepared by S1 and dissolve it in 60g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H6. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0077] Example 9 The difference from Example 1 is that in the sulfur-containing polyamino acid, m=30, n=10, and the corrosion inhibitor is designated as H7.

[0078] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0079] S2, Preparation of sulfur-containing polyamino acids: 3-(methylthio)-1-propylamine hydrochloride and glyoxylic acid aqueous solution with a molar ratio of 1:2 were mixed with HCl with a concentration of 2 mol / L. The mixture was then reacted at a reflux temperature of 100℃ for 10 h. The solvent was removed by evaporation and purified with acetone to obtain N-3-(methylthio)propylglycine hydrochloride of formula I.

[0080] NaOH was dissolved in 400 mL of water, and N-3-(methylthio)propylglycine hydrochloride of Formula I and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II were added with stirring. After reacting for 48 h, 60 mL of concentrated hydrochloric acid with a mass concentration of 36%~38% was added for acidification, followed by washing, drying, and concentration under reduced pressure. 0.3 mol of PBr3 was added dropwise with stirring, and the mixture was cooled in an ice bath to obtain compound of Formula III. The molar ratio of NaOH, N-3-(methylthio)propylglycine hydrochloride of Formula I, and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II was 2:1:1.

[0081] NaOH was dissolved in 400 mL of water, and sarcosine and S-ethoxythiocarbonyl mercaptoacetic acid of formula II were added under stirring. After reacting for 72 h, 60 mL of concentrated hydrochloric acid with a mass concentration of 36%–38% was added for acidification. The mixture was washed, dried, and concentrated under reduced pressure. The product was then dissolved in 350 mL of dry chloroform, and 0.3 mol of PBr3 was added dropwise under stirring. The mixture was cooled in an ice bath. After the reaction was complete, the mixture was cooled and stirred for 30 min. The mixture was then washed, dried, concentrated under reduced pressure, and vacuum distilled to obtain the compound of formula IV. The molar ratio of NaOH, sarcosine, and S-ethoxythiocarbonyl mercaptoacetic acid of formula II was 2.5:1:1.

[0082] 0.3 g of compound III was dissolved in 3.0 mL of anhydrous THF, and 2.14 mg of 0.08 M benzylamine solution was added. The mixture was reacted in an oil bath at 50 °C for 36 h. Then, compound IV was added at a molar ratio of 1:0.33 (compound III to compound IV), and the reaction was continued for another 30 h. The mixture was then purified by precipitation with diethyl ether and dried under vacuum to obtain compound V, which is a sulfur-containing polyamino acid with the following structural formula: .

[0083] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 0.7wt%.

[0084] Example 10 The difference compared to Example 1 is that in the sulfur-containing polyamino acid, m=25, n=25, and the corrosion inhibitor is denoted as H8.

[0085] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0086] S2, Preparation of sulfur-containing polyamino acids: 3-(methylthio)-1-propylamine hydrochloride and glyoxylic acid aqueous solution with a molar ratio of 1:2 were mixed with HCl with a concentration of 2 mol / L. The mixture was then reacted at a reflux temperature of 100℃ for 10 h. The solvent was removed by evaporation and purified with acetone to obtain N-3-(methylthio)propylglycine hydrochloride of formula I.

[0087] NaOH was dissolved in 400 mL of water, and N-3-(methylthio)propylglycine hydrochloride of Formula I and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II were added with stirring. After reacting for 48 h, 40 mL of concentrated hydrochloric acid with a mass concentration of 36%~38% was added for acidification, followed by washing, drying, and concentration under reduced pressure. 0.3 mol of PBr3 was added dropwise with stirring, and the mixture was cooled in an ice bath to obtain compound of Formula III. The molar ratio of NaOH, N-3-(methylthio)propylglycine hydrochloride of Formula I, and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II was 2:1:1.

[0088] NaOH was dissolved in 400 mL of water, and sarcosine and S-ethoxythiocarbonyl mercaptoacetic acid of formula II were added under stirring. After reacting for 72 h, 40 mL of concentrated hydrochloric acid with a mass concentration of 36%–38% was added for acidification. The mixture was washed, dried, and concentrated under reduced pressure. The product was then dissolved in 350 mL of dry chloroform, and 0.3 mol of PBr3 was added dropwise under stirring. The mixture was cooled in an ice bath. After the reaction was complete, the mixture was cooled and stirred for 30 min. The mixture was then washed, dried, concentrated under reduced pressure, and vacuum distilled to obtain the compound of formula IV. The molar ratio of NaOH, sarcosine, and S-ethoxythiocarbonyl mercaptoacetic acid of formula II was 2.5:1:1.

[0089] 0.3 g of compound III was dissolved in 3.0 mL of anhydrous THF, and 2.14 mg of 0.08 M benzylamine solution was added. The mixture was reacted in an oil bath at 50 °C for 36 h. Then, compound IV was added at a molar ratio of 1:1 to compound IV, and the reaction was continued for another 30 h. The mixture was then purified by precipitation with diethyl ether and dried under vacuum to obtain compound V, which is a sulfur-containing polyamino acid with the following structural formula: .

[0090] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 0.7wt%.

[0091] Example 11 The difference compared to Example 1 is that in the sulfur-containing polyamino acid, m=10, n=50, and the corrosion inhibitor is designated as H9.

[0092] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0093] S2, Preparation of sulfur-containing polyamino acids: 3-(methylthio)-1-propylamine hydrochloride and glyoxylic acid aqueous solution with a molar ratio of 1:2 were mixed with HCl with a concentration of 2 mol / L. The mixture was then reacted at a reflux temperature of 100℃ for 10 h. The solvent was removed by evaporation and purified with acetone to obtain N-3-(methylthio)propylglycine hydrochloride of formula I.

[0094] NaOH was dissolved in 400 mL of water, and N-3-(methylthio)propylglycine hydrochloride of Formula I and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II were added with stirring. After reacting for 48 h, 50 mL of concentrated hydrochloric acid with a mass concentration of 36%~38% was added for acidification, followed by washing, drying, and concentration under reduced pressure. 0.3 mol of PBr3 was added dropwise under stirring, and the mixture was cooled in an ice bath to obtain compound of Formula III. The molar ratio of NaOH, N-3-(methylthio)propylglycine hydrochloride of Formula I, and S-ethoxythiocarbonyl mercaptoacetic acid of Formula II was 2:1:1.

[0095] NaOH was dissolved in 400 mL of water, and sarcosine and S-ethoxythiocarbonyl mercaptoacetic acid of formula II were added under stirring. After reacting for 72 h, 50 mL of concentrated hydrochloric acid with a mass concentration of 36%–38% was added for acidification. The mixture was washed, dried, and concentrated under reduced pressure. The product was then dissolved in 350 mL of dry chloroform, and 0.3 mol of PBr3 was added dropwise under stirring. The mixture was cooled in an ice bath. After the reaction was complete, the mixture was cooled and stirred for 30 min. The mixture was then washed, dried, concentrated under reduced pressure, and vacuum distilled to obtain the compound of formula IV. The molar ratio of NaOH, sarcosine, and S-ethoxythiocarbonyl mercaptoacetic acid of formula II was 2.5:1:1.

[0096] 0.3 g of compound III was dissolved in 3.0 mL of anhydrous THF, and 2.14 mg of 0.08 M benzylamine solution was added. The mixture was reacted in an oil bath at 50 °C for 36 h. Then, compound IV was added at a molar ratio of 1:5 (compound III to compound IV), and the reaction was continued for another 30 h. The mixture was then purified by precipitation with diethyl ether and dried under vacuum to obtain compound V, which is a sulfur-containing polyamino acid with the following structural formula: .

[0097] S3: Weigh 30g of the Mannich base prepared by S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain a primary corrosion inhibitor. Then add 20g of the sulfur-containing polyamino acid prepared by S2 and continue stirring until homogeneous to obtain a carbon steel acid corrosion inhibitor, denoted as H1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added was 0.7wt%.

[0098] To further illustrate the technical effects of the present invention, a comparative example is also provided, as follows.

[0099] Comparative Example 1 Compared with Example 1, the difference is that 50g of the Mannich base prepared by S1 was weighed and dissolved in 50g of N,N-dimethylformamide and stirred evenly to obtain a carbon steel acid corrosion inhibitor, denoted as D1.

[0100] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, Mannich base, same as in Example 1.

[0101] S2: Weigh 50g of Mannich base of S1 and dissolve it in 50g of N,N-dimethylformamide, stirring until homogeneous to obtain carbon steel acid corrosion inhibitor, denoted as D1. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0102] Comparative Example 2 Compared with Example 1, the difference is that 50g of sulfur-containing polyamino acid prepared by S2 was weighed and dissolved in 50g of N,N-dimethylformamide and stirred evenly to obtain carbon steel acid corrosion inhibitor, denoted as D2.

[0103] A method for preparing an acid corrosion inhibitor for carbon steel includes the following steps: S1, sulfur-containing polyamino acid, is the same as in Example 1.

[0104] S2: Weigh 50g of the sulfur-containing polyamino acid prepared by S1 and dissolve it in 50g of N,N-dimethylformamide and stir evenly to obtain a carbon steel acid corrosion inhibitor, denoted as D2. In the corrosion test, the amount of carbon steel acid corrosion inhibitor added is 0.7wt%.

[0105] The carbon steel acid corrosion inhibitors prepared according to the above embodiments and comparative examples of the present invention were used for corrosion protection of carbon steel in an acid system, and compared with a control group without the addition of corrosion inhibitors. Specifically, the test material was N80 carbon steel, the test temperature was 90℃, and the acid system used in the test was a 15% hydrochloric acid solution and a 20% hydrochloric acid solution. The corrosion protection performance is shown in Table 1 below.

[0106] Table 1. Comparison of the anti-corrosion effects of the corrosion inhibitors in the embodiments and comparative examples of the present invention. As shown in Table 1, the present invention exhibits excellent corrosion inhibition of carbon steel in hydrochloric acid media. Furthermore, the low concentration of the solution effectively protects the service safety of the tubing during acidification and production enhancement, achieving cost reduction and efficiency improvement. A comparison of the corrosion inhibition performance of the examples with Comparative Examples 1 and 2 reveals that the Mannich base and sulfur-containing polyamino acids used in the present invention have a good synergistic effect, enhancing the density of the film.

[0107] Using N80 material as the test steel, Figure 1 The graph shows a comparison of the corrosion inhibition effects of no corrosion inhibitor (blank control) and the corrosion inhibitors added in Examples 1, 6, 2, and 2. Figures 2-7 The macroscopic corrosion morphology of the N80 material sample surface after film removal is shown in the figure after corrosion inhibition tests were conducted on samples without corrosion inhibitors and with various types of corrosion inhibitors from the embodiments or comparative examples of this invention. As can be seen from the figure, the corrosion of the N80 material was extremely severe in the test without corrosion inhibitors, mainly uniform corrosion, with prominent pitting corrosion in some areas. After adding corrosion inhibitors, the corrosion was significantly slowed down, the corrosion rate dropped sharply, and the corrosion inhibition rate reached more than 97%, showing a significant corrosion inhibition effect. However, the overall corrosion rate of the comparative examples was significantly higher than that of the embodiments. The corrosion rate of Comparative Example 2 was 4.5 times that of Example 1. Furthermore, the surface corrosion of the N80 material samples of Examples 1 and 6 was relatively slight, and machining marks were still visible. However, the surface of the sample of Comparative Example 2 was significantly more severely corroded and had become rough.

[0108] In summary, the carbon steel acid corrosion inhibitor provided by this invention can form a strong and dense adsorption film in a high-temperature, strongly acidic environment, significantly inhibiting uniform corrosion and pitting corrosion of carbon steel. It achieves excellent corrosion inhibition effects at a relatively low addition amount (0.5wt%~1wt%), effectively reducing the cost of using acid corrosion inhibitors. Furthermore, this corrosion inhibitor formulation is surfactant-free, avoiding foaming problems, and contains no organochlorine components, meeting the environmental and safety requirements of oilfields and demonstrating promising industrial application prospects.

[0109] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A carbon steel acidizing corrosion inhibitor characterized in that, The carbon steel acid corrosion inhibitor is a mixture of Mannich base as the main agent, sulfur-containing polyamino acid as the synergist, and solvent. The Mannich base is ; The sulfur-containing polyamino acid is wherein m is 10-30 and n is 6-50. The mass ratio of the Mannich base, sulfur-containing polyamino acid, and solvent is 1~3:1:2.5~7.

2. The carbon steel pickling inhibitor according to claim 1, characterized in that, The solvent is N,N-dimethylformamide, tetrahydrofuran, N,N-dimethylacetamide, or ethylene glycol monobutyl ether.

3. The carbon steel acid corrosion inhibitor according to claim 1, characterized in that, The Mannich base is prepared by reacting benzamide, aniline and formaldehyde in an alcohol solvent at a molar ratio of 1:1:1.2~2 for 6h~12h at 60℃~80℃.

4. A method for preparing the carbon steel acid corrosion inhibitor according to any one of claims 1 to 3, characterized in that, Includes the following steps: Using Mannich base as the main agent, a primary corrosion inhibitor is formed by mixing it with a solvent. The primary corrosion inhibitor is then mixed with sulfur-containing polyamino acids to obtain a carbon steel acidification corrosion inhibitor.

5. The application of the carbon steel acid corrosion inhibitor according to any one of claims 1 to 3 in the corrosion protection of carbon steel, characterized in that, The application method is as follows: the carbon steel acid corrosion inhibitor is added to the acid solution to form an anti-corrosion solution, and the carbon steel is immersed in the anti-corrosion solution for carbon steel corrosion protection.

6. The application according to claim 5, characterized in that, The amount of the carbon steel acid corrosion inhibitor added is 0.5wt%~1wt% based on the mass of the acid solution.

7. The application according to claim 5, characterized in that, The mass concentration of the acid solution is 15wt%~20wt%.

8. The application according to claim 7, characterized in that, The acid solution is hydrochloric acid.

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