Octadecylamine-based film-forming corrosion inhibitor and preparation method thereof

Abstract

The invention discloses a film-forming corrosion inhibitor based on octadecylamine and a preparation method thereof, and relates to the technical field of film-forming corrosion inhibitors. The preparation method specifically comprises the following steps: S1, weighing octadecylamine, a film-forming agent, thiourea and pyridine according to a ratio for later use; s2, adding octadecylamine into half of pyridine, and uniformly stirring to obtain an octadecylamine pyridine solution; s3, adding the film-forming agent into the remaining half of pyridine, uniformly stirring, dropwise adding the octadecylamine pyridine solution in the step S2, and stirring to obtain a mixed solution; s4, adding thiourea into the mixed solution in the step S3, uniformly stirring, adding water for dilution, and adjusting the pH value to obtain a film-forming corrosion inhibitor; the film-forming corrosion inhibitor has a good film-forming corrosion inhibition effect under a low-temperature condition.

Description

Technical Field

[0001] The present invention relates to the technical field of film-forming corrosion inhibitors, and particularly to a film-forming corrosion inhibitor based on octadecylamine and a preparation method thereof. Background Technique

[0002] During the shutdown period of boilers (such as during maintenance, seasonal shutdown, or standby state), due to the influence of residual moisture, oxygen, and environmental humidity inside, metal corrosion problems are extremely likely to occur. Shutdown corrosion is mainly manifested as oxygen corrosion and acidic condensate corrosion, and its products (such as iron oxide) will not only reduce the boiler thermal efficiency and block pipelines, but also cause local pitting or stress corrosion cracking when the boiler is restarted, seriously threatening the equipment safety and service life.

[0003] The molecular formula of octadecylamine is C 18 H 37 NH2, which is a long-chain alkylamine. The amino group at the molecular end can form a coordination bond with metal atoms on the metal surface, thereby forming a hydrophobic protective film on the metal surface. This protective film can effectively isolate oxygen, carbon dioxide, and corrosive ions in water in the air, preventing metal corrosion. Therefore, it is mainly used for the shutdown protection of thermal systems, such as the anti-corrosion of equipment such as boilers, steam turbines, and pipelines.

[0004] However, octadecylamine has extremely poor solubility in water. When used for the shutdown protection of boilers, it needs to reach 300 - 450 °C to vaporize, so as to achieve a better film-forming effect. The film-forming effect is poor at low temperatures and cannot play a corrosion inhibition effect. Although the prior art uses the method of compounding corrosion inhibitors to enhance its film-forming corrosion inhibition effect at low temperatures, it is still difficult to meet the requirements.

[0005] In summary, to solve the above problems, it is of great significance to provide a film-forming corrosion inhibitor based on octadecylamine and a preparation method thereof with good film-forming corrosion inhibition effect at low temperatures. Summary of the Invention

[0006] The purpose of the present invention is to provide a film-forming corrosion inhibitor based on octadecylamine and a preparation method thereof to solve the problems raised in the prior art.

[0007] To achieve the above purpose, the present invention provides the following technical solutions:

[0008] A preparation method of a film-forming corrosion inhibitor based on octadecylamine, comprising the following steps:

[0009] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio and set aside;

[0010] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution;

[0011] S3: Add the film-forming agent to the remaining half of the pyridine and stir evenly. Then, dropwise add the octadecylamine pyridine solution from step S2 and stir to obtain a mixed solution.

[0012] S4: Add thiourea to the mixed solution from step S3 and stir evenly. Then, dilute with water and adjust the pH to obtain the film-forming corrosion inhibitor.

[0013] More preferably, the specific steps of step S3 are as follows: Add the film-forming agent to the remaining half of the pyridine and stir evenly. Heat to 40 - 45 °C, then dropwise add the octadecylamine pyridine solution from step S2, control the time to 15 - 20 min, and stir for 1 - 2 h after the addition is completed to obtain a mixed solution.

[0014] More preferably, the film-forming corrosion inhibitor comprises the following substances: 60 - 80 mg / L octadecylamine, 100 - 120 mg / L film-forming agent, 15 - 20 mg / L thiourea, 5 - 6 mL pyridine, and the solvent is deionized water.

[0015] More preferably, the pH of the film-forming corrosion inhibitor is 9 - 9.5.

[0016] More preferably, the preparation method of the film-forming agent comprises the following steps:

[0017] (1) After mixing fatty acid and diethylenetriamine, first stir and react at 180 - 190 °C for 2 - 2.5 h, then stir at 220 - 230 °C for 2 - 3 h to obtain an imidazoline compound.

[0018] (2) Add tetra-arm polyethylene glycol and potassium hydroxide to deionized water, stir at 90 - 95 °C for 2 - 3 h, cool down to 1 - 5 °C, dropwise add epichlorohydrin within 2 - 3 h, stir for 2 - 3 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-arm polyethylene glycol.

[0019] (3) Add β-cyclodextrin to 3.5 wt% sodium hydroxide aqueous solution and stir evenly. Add epoxidized tetra-arm polyethylene glycol, stir at 35 - 40 °C for 18 - 24 h, add the imidazoline compound, stir at 50 - 55 °C for 12 - 16 h, neutralize, add absolute ethanol for precipitation, filter, and dry to obtain the film-forming agent.

[0020] More preferably, the imidazoline compound comprises fatty acid and diethylenetriamine with a molar ratio of 1:1.2 - 1.3.

[0021] The epoxidized tetra-arm polyethylene glycol comprises the following raw materials, by mass: 9 - 11 parts of tetra-arm polyethylene glycol, 2 - 3 parts of potassium hydroxide, 25 - 30 parts of deionized water, 3.6 - 3.8 parts of epichlorohydrin.

[0022] The film-forming agent comprises the following raw materials in parts by mass: 23 to 24 parts of β-cyclodextrin, 140 to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, 15 to 16 parts of epoxidized tetra-armed polyethylene glycol, and 6.5 to 7 parts of imidazoline compound.

[0023] More preferably, the fatty acid is one of C12 - C18; the molecular weight of the tetra-armed polyethylene glycol is 1000 - 2000.

[0024] Compared with the prior art, the beneficial effects of this application are as follows:

[0025] (1) In the present invention, by using β-cyclodextrin to encapsulate octadecylamine, its solubility in water is increased: β-cyclodextrin is composed of 7 D-glucopyranose units. The internal cavity is composed of hydrogen atoms and C-H bonds of the glucose units, showing hydrophobicity, while the external hydroxyl groups are hydrophilic and can be used to encapsulate organic small molecules, improving their solubility in water.

[0026] (2) Tetra-armed polyethylene glycol has abundant ether groups and can form chelates with iron ions on the metal surface to promote film formation. Its branched structure helps the molecular chain to unfold on the metal surface, further improving the film-forming ability. In the present invention, by epoxidizing tetra-armed polyethylene glycol, β-cyclodextrin is grafted and introduced, and octadecylamine is coated by β-cyclodextrin, thereby improving the water solubility of octadecylamine while enhancing the dispersibility and film-forming effect, and thus improving the corrosion inhibition performance. At the same time, the molecular weight of tetra-armed polyethylene glycol should not be too large, as excessive molecular weight may lead to chain entanglement and aggregation, reducing the dispersibility instead. The most suitable molecular weight is 1000 - 2000.

[0027] (3) In the present invention, by continuously reacting fatty acid and diethylenetriamine by heating, an imidazoline compound is finally formed. The imidazole ring contains multiple nitrogen atoms, which can provide lone pair electrons to form coordination bonds with the metal surface, thereby achieving chemical adsorption. Similarly, using the amino group on this compound to graft on tetra-armed polyethylene glycol enhances the film-forming effect, thus improving the film-forming corrosion inhibition performance. At the same time, the chain segment of the fatty acid should be controlled within C12 - C18, which can have a synergistic film-forming corrosion inhibition effect with octadecylamine molecules. Too short or too long chain segments are likely to cause film-forming defects and a decline in the corrosion inhibition effect. Detailed implementation manners

[0028] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0029] It should be noted that there are no special restrictions on the purchasing manufacturers of all raw materials involved in the present invention. Exemplarily, they include: the CAS number of palmitic acid: 57-10-3; the CAS number of diethylenetriamine: 111-40-0; four-arm polyethylene glycol with a molecular weight of 1000-2000, provided by Guangdong Wengjiang Chemical Reagent Co., Ltd.; the CAS number of epichlorohydrin: 106-89-8; the CAS number of β-cyclodextrin: 7585-39-9; the CAS number of octadecylamine: 124-30-1; the CAS number of thiourea: 62-56-6; the CAS number of pyridine: 110-86-1.

[0030] Among them, in the following examples, "parts" refers to parts by mass, and the raw materials mentioned above and used below but not mentioned are all commercially available.

[0031] Example 1: Step 1: Preparation of the film-forming agent:

[0032] (1) After mixing 2.55 parts of palmitic acid and 1.3 parts of diethylenetriamine, first stir and react at 185 °C for 2 h, and then stir at 225 °C for 2.5 h to obtain an imidazoline compound;

[0033] (2) Add 10 parts of four-arm polyethylene glycol and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool to 3 °C, and dropwise add 3.7 parts of epichlorohydrin within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized four-arm polyethylene glycol;

[0034] (3) Add 23.5 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, stir evenly, add 15.5 parts of epoxidized four-arm polyethylene glycol, stir at 40 °C for 20 h, add 6.7 parts of imidazoline compound, stir at 55 °C for 14 h, neutralize, add absolute ethanol for precipitation, filter, and dry to obtain the film-forming agent;

[0035] Step 2: Preparation of the film-forming corrosion inhibitor:

[0036] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio and set aside;

[0037] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution;

[0038] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, dropwise add the octadecylamine pyridine solution in step S2, control the time to 15 min, stir for 1.5 h, and stir for 1.5 h after the addition is completed to obtain a mixed solution;

[0039] S4: Add thiourea to the mixed solution in step S3, stir evenly, add water for dilution, and adjust the pH to obtain the film-forming corrosion inhibitor.

[0040] The film-forming corrosion inhibitor includes the following substances: 70 mg / L octadecylamine, 110 mg / L film-forming agent, 15 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0041] Example 2: Step 1: Preparation of film-forming agent:

[0042] (1) After mixing 2.55 parts of palmitic acid and 1.3 parts of diethylenetriamine, the mixture was stirred at 185° C. for 2 hours and then stirred at 225° C. for 2.5 hours to obtain an imidazoline compound;

[0043] (2) 10 parts of four-arm polyethylene glycol and 2.5 parts of potassium hydroxide were added to 25 parts of deionized water and stirred at 95° C. for 2.5 hours, cooled to 3° C., 3.7 parts of epichlorohydrin were added dropwise within 2 hours, stirred for 2.5 hours, concentrated under reduced pressure, and dried to obtain epoxidized four-arm polyethylene glycol;

[0044] (3) adding 23.5 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution and stirring evenly, adding 15.5 parts of epoxidized four-arm polyethylene glycol, stirring at 40° C. for 20 h, adding 6.7 parts of imidazoline compound, stirring at 55° C. for 14 h, neutralizing, adding anhydrous ethanol for precipitation, filtering, and drying to obtain a film-forming agent;

[0045] Step 2: Preparation of film-forming corrosion inhibitor:

[0046] S1: Weigh octadecylamine, film-forming agent, thiourea and pyridine according to the proportions for later use;

[0047] S2: adding octadecylamine to half of pyridine and stirring evenly to obtain an octadecylamine pyridine solution;

[0048] S3: Add the film-forming agent to the remaining half of the pyridine and stir evenly, heat to 40°C, add the octadecylamine pyridine solution of step S2 dropwise, control the time to 15min, stir for 1.5h, stir for 1.5h after the addition is completed, to obtain a mixed solution;

[0049] S4: adding thiourea to the mixed solution of step S3, stirring evenly, diluting with water, and adjusting the pH to obtain a film-forming corrosion inhibitor.

[0050] The film-forming corrosion inhibitor includes the following substances: 60 mg / L octadecylamine, 100 mg / L film-forming agent, 15 mg / L thiourea, 5 mL pyridine, and the solvent is deionized water.

[0051] Example 3: Step 1: Preparation of film-forming agent:

[0052] (1) After mixing 2.55 parts of palmitic acid and 1.3 parts of diethylenetriamine, the mixture was stirred at 185° C. for 2 hours and then stirred at 225° C. for 2.5 hours to obtain an imidazoline compound;

[0053] (2) Add 10 parts of tetra-arm polyethylene glycol and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool down to 3 °C, dropwise add 3.7 parts of epichlorohydrin within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-arm polyethylene glycol;

[0054] (3) Add 23.5 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, stir evenly, add 15.5 parts of epoxidized tetra-arm polyethylene glycol, stir at 40 °C for 20 h, add 6.7 parts of imidazoline compound, stir at 55 °C for 14 h, neutralize, add absolute ethanol to precipitate, filter, and dry to obtain a film-forming agent;

[0055] Step Two: Preparation of film-forming corrosion inhibitor:

[0056] S1: Weigh stearylamine, film-forming agent, thiourea, and pyridine according to the ratio for standby;

[0057] S2: Add stearylamine to half of the pyridine and stir evenly to obtain a stearylamine pyridine solution;

[0058] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, dropwise add the stearylamine pyridine solution in Step S2, control the time to 15 min, stir for 1.5 h, and stir for 1.5 h after the addition is completed to obtain a mixed solution;

[0059] S4: Add thiourea to the mixed solution in Step S3, stir evenly, dilute with water, and adjust the pH to obtain a film-forming corrosion inhibitor.

[0060] Among them, the film-forming corrosion inhibitor includes the following substances: 80 mg / L stearylamine, 120 mg / L film-forming agent, 20 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0061] Comparative Example 1: Based on Example 1, the molecular weight of tetra-arm polyethylene glycol is 6000 - 8000, and the rest of the process remains unchanged. Specifically as follows: Step One: Preparation of film-forming agent:

[0062] (1) Mix 2.55 parts of palmitic acid and 1.3 parts of diethylenetriamine, first stir and react at 185 °C for 2 h, and then stir at 225 °C for 2.5 h to obtain an imidazoline compound;

[0063] (2) Add 10 parts of tetra-arm polyethylene glycol (molecular weight 6000 - 8000) and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool down to 3 °C, dropwise add 3.7 parts of epichlorohydrin within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-arm polyethylene glycol;

[0064] (3) Add 23.5 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, stir evenly, add 15.5 parts of epoxidized tetra-arm polyethylene glycol, stir at 40 °C for 20 h, add 6.7 parts of imidazoline compound, stir at 55 °C for 14 h, neutralize, add anhydrous ethanol to precipitate, filter, and dry to obtain a film-forming agent;

[0065] Step 2: Preparation of film-forming corrosion inhibitor:

[0066] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio and set aside;

[0067] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution;

[0068] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, and gradually add the octadecylamine pyridine solution in Step S2, control the time to 15 min, stir for 1.5 h, and stir for 1.5 h after the addition is completed to obtain a mixed solution;

[0069] S4: Add thiourea to the mixed solution in Step S3, stir evenly, add water for dilution, and adjust the pH to obtain a film-forming corrosion inhibitor.

[0070] Among them, the film-forming corrosion inhibitor includes the following substances: 70 mg / L octadecylamine, 110 mg / L film-forming agent, 15 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0071] Comparative Example 2: Based on Example 1, palmitic acid is replaced with caproic acid, and the rest of the process remains unchanged. Specifically as follows: Step 1: Preparation of film-forming agent:

[0072] (1) After mixing 1.15 parts of caproic acid and 1.3 parts of diethylenetriamine, first stir and react at 185 °C for 2 h, and then stir at 225 °C for 2.5 h to obtain an imidazoline compound;

[0073] (2) Add 10 parts of tetra-arm polyethylene glycol and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool to 3 °C, and gradually add 3.7 parts of epichlorohydrin dropwise within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-arm polyethylene glycol;

[0074] (3) Add 23.5 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, stir evenly, add 15.5 parts of epoxidized tetra-arm polyethylene glycol, stir at 40 °C for 20 h, add 6.7 parts of imidazoline compound, stir at 55 °C for 14 h, neutralize, add anhydrous ethanol to precipitate, filter, and dry to obtain a film-forming agent;

[0075] Step 2: Preparation of film-forming corrosion inhibitor:

[0076] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio and set them aside.

[0077] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution.

[0078] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, and gradually add the octadecylamine pyridine solution from step S2, controlling the time to 15 min, stirring for 1.5 h, and stirring for another 1.5 h after the addition is completed to obtain a mixed solution.

[0079] S4: Add thiourea to the mixed solution from step S3, stir evenly, add water for dilution, and adjust the pH to obtain a film-forming corrosion inhibitor.

[0080] Among them, the film-forming corrosion inhibitor includes the following substances: 70 mg / L octadecylamine, 110 mg / L film-forming agent, 15 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0081] Comparative Example 3: Based on Example 1, without grafting β-cyclodextrin and imidazoline compound, directly add them, and the rest of the process remains unchanged. The specific steps are as follows: Step 1: Preparation of the film-forming agent:

[0082] (1) Mix 2.55 parts of palmitic acid and 1.3 parts of diethylenetriamine, first stir and react at 185 °C for 2 h, and then stir at 225 °C for 2.5 h to obtain an imidazoline compound.

[0083] (2) Add 10 parts of tetra-armed polyethylene glycol and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool to 3 °C, gradually add 3.7 parts of epichlorohydrin dropwise within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-armed polyethylene glycol.

[0084] (3) Mix 23.5 parts of β-cyclodextrin, 15.5 parts of epoxidized tetra-armed polyethylene glycol, and 6.7 parts of imidazoline compound evenly to obtain a film-forming agent.

[0085] Step 2: Preparation of the film-forming corrosion inhibitor:

[0086] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio and set them aside.

[0087] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution.

[0088] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, and gradually add the octadecylamine pyridine solution from step S2, controlling the time to 15 min, stirring for 1.5 h, and stirring for another 1.5 h after the addition is completed to obtain a mixed solution.

[0089] S4: Add thiourea to the mixed solution in step S3, stir evenly, dilute with water, and adjust the pH to obtain a film-forming corrosion inhibitor.

[0090] Among them, the film-forming corrosion inhibitor includes the following substances: 70 mg / L octadecylamine, 110 mg / L film-forming agent, 15 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0091] Comparative example 4: Based on Example 1, the four-arm polyethylene glycol is not grafted with imidazoline compound, and the rest of the process remains unchanged. Specifically as follows: Step one: Preparation of the film-forming agent:

[0092] (1) Add 10 parts of four-arm polyethylene glycol and 2.5 parts of potassium hydroxide to 25 parts of deionized water, stir at 95 °C for 2.5 h, cool down to 3 °C, dropwise add 3.7 parts of epichlorohydrin within 2 h, stir for 2.5 h, concentrate under reduced pressure, and dry to obtain epoxidized four-arm polyethylene glycol;

[0093] (2) Add 47 parts of β-cyclodextrin to 150 parts of 3.5 wt% sodium hydroxide aqueous solution, stir evenly, add 15.5 parts of epoxidized four-arm polyethylene glycol, stir at 40 °C for 20 h, neutralize, add absolute ethanol for precipitation, filter, and dry to obtain the film-forming agent;

[0094] Step two: Preparation of the film-forming corrosion inhibitor:

[0095] S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio for standby;

[0096] S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution;

[0097] S3: Add the film-forming agent to the remaining half of the pyridine, stir evenly, heat to 40 °C, dropwise add the octadecylamine pyridine solution in step S2, control the time to 15 min, stir for 1.5 h, and stir for 1.5 h after the addition is completed to obtain a mixed solution;

[0098] S4: Add thiourea to the mixed solution in step S3, stir evenly, dilute with water, and adjust the pH to obtain a film-forming corrosion inhibitor.

[0099] Among them, the film-forming corrosion inhibitor includes the following substances: 70 mg / L octadecylamine, 110 mg / L film-forming agent, 15 mg / L thiourea, 6 mL pyridine, and the solvent is deionized water.

[0100] Performance test: After degreasing, grinding, washing, and drying the 20# carbon steel standard corrosion test piece, according to GB / T18175-2014, immerse it in the film-forming corrosion inhibitor prepared in each example and comparative example, and use the rotating hanging piece method to simulate flowing condensed water at a temperature of 60 °C for 72 h. Calculate the corrosion inhibition rate by measuring the mass difference. The experimental data are shown in Table 1.

[0101] Table 1

[0102]

[0103]

[0104] Conclusion: It can be seen from Table 1 that in Comparative Example 1, the molecular weight of tetra-arm polyethylene glycol was increased, the probability of chain entanglement and aggregation increased, the dispersity decreased, and the film-forming corrosion inhibition effect also decreased; in Comparative Example 2, palmitic acid was replaced by caproic acid, the carbon chain length was relatively low, and the synergistic effect with octadecylamine molecules was poor, there were defects in the corrosion inhibition film, and the corrosion inhibition rate decreased; in Comparative Example 3, β-cyclodextrin and imidazoline compounds were not grafted but directly added, the dispersity of the corrosion inhibition film-forming molecules in the system was greatly reduced, and the film-forming corrosion inhibition performance decreased significantly; in Comparative Example 4, tetra-arm polyethylene glycol was not grafted with imidazoline compounds but only with β-cyclodextrin, and the film-forming corrosion inhibition effect was not as good as that of Example 1.

[0105] In summary, the present invention prepared a film-forming agent by grafting β-cyclodextrin and imidazoline compounds using tetra-arm polyethylene glycol based on octadecylamine, and compounded it with octadecylamine, and successfully prepared a film-forming corrosion inhibitor based on octadecylamine and its preparation method, which has good film-forming corrosion inhibition performance under low-temperature conditions.

[0106] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a film-forming corrosion inhibitor based on octadecylamine, characterized in that: It includes the following steps: S1: Weigh octadecylamine, film-forming agent, thiourea, and pyridine according to the ratio for standby; S2: Add octadecylamine to half of the pyridine and stir evenly to obtain an octadecylamine pyridine solution; S3: Add the film-forming agent to the remaining half of the pyridine and stir evenly. Then, dropwise add the octadecylamine pyridine solution obtained in step S2 and stir to obtain a mixed solution; S4: Add thiourea to the mixed solution obtained in step S3 and stir evenly. Add water for dilution and adjust the pH to obtain a film-forming corrosion inhibitor.

2. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 1, characterized in that: The specific steps of step S3 are as follows: Add the film-forming agent to the remaining half of the pyridine and stir evenly. Heat to 40 - 45 °C, dropwise add the octadecylamine pyridine solution obtained in step S2, control the time for 15 - 20 min, and stir for 1 - 2 h after the dropping is completed to obtain a mixed solution.

3. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 1, characterized in that: The film-forming corrosion inhibitor includes the following substances: 60 - 80 mg / L octadecylamine, 100 - 120 mg / L film-forming agent, 15 - 20 mg / L thiourea, 5 - 6 mL pyridine, and the solvent is deionized water.

4. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 1, characterized in that: The pH of the film-forming corrosion inhibitor is 9 - 9.

5.

5. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 1, characterized in that: The preparation method of the film-forming agent includes the following steps: (1) Mix fatty acid and diethylenetriamine, first stir and react at 180 - 190 °C for 2 - 2.5 h, and then stir at 220 - 230 °C for 2 - 3 h to obtain an imidazoline compound; (2) Add tetra-armed polyethylene glycol and potassium hydroxide to deionized water and stir at 90 - 95 °C for 2 - 3 h. Cool down to 1 - 5 °C, dropwise add epichlorohydrin within 2 - 3 h, stir for 2 - 3 h, concentrate under reduced pressure, and dry to obtain epoxidized tetra-armed polyethylene glycol; (3) Add β-cyclodextrin to 3.5 wt% sodium hydroxide aqueous solution and stir evenly. Add epoxidized tetra-armed polyethylene glycol, stir at 35 - 40 °C for 18 - 24 h, add the imidazoline compound, stir at 50 - 55 °C for 12 - 16 h, neutralize, add absolute ethanol for precipitation, filter, and dry to obtain the film-forming agent.

6. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 5, characterized in that: The imidazoline compound includes fatty acid and diethylenetriamine with a molar ratio of 1:1.2 - 1.3; The epoxidized tetra-armed polyethylene glycol includes the following raw materials, by mass: 9 - 11 parts of tetra-armed polyethylene glycol, 2 - 3 parts of potassium hydroxide, 25 - 30 parts of deionized water, 3.6 - 3.8 parts of epichlorohydrin; The film-forming agent includes the following raw materials, by mass: 23 - 24 parts of β-cyclodextrin, 140 - 150 parts of 3.5 wt% sodium hydroxide aqueous solution, 15 - 16 parts of epoxidized tetra-armed polyethylene glycol, 6.5 - 7 parts of imidazoline compound.

7. The preparation method of a film-forming corrosion inhibitor based on octadecylamine according to claim 5, characterized in that: The fatty acid includes one of C12 - C18; the molecular weight of the tetra-armed polyethylene glycol is 1000 - 2000.

8. Prepared according to the preparation method of a film-forming corrosion inhibitor based on octadecylamine described in any one of claims 1 - 7.

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