A fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, and its preparation method and application

Abstract

The present invention belongs to the fields of chemistry, materials science, and corrosion engineering, and discloses a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycles, as well as its preparation method and application. A simple and efficient Schiff base reaction is used to introduce a five-membered furan ring into the fluorophore coumarin. The Schiff base carbon-nitrogen double bond and the furan heterocycle, as well as the oxygen heteroatom of the fluorophore coumarin itself, are utilized to coordinate well with iron ions. This not only achieves metal corrosion inhibition, but also makes it possible to detect the amount of corrosion inhibitor used through fluorescence, avoiding environmental pollution caused by excessive use. The fluorescent metal corrosion inhibitor has an inhibition concentration of 7×10 ‑5 mol / L, it exhibits the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%.

Description

Technical Field

[0001] The invention belongs to the fields of chemistry, material science and corrosion engineering, and relates to a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, and a preparation method and application thereof. Background Art

[0002] Metal corrosion is a widespread problem, particularly in industrial production. Corrosion of metal equipment not only affects its service life but can also lead to safety incidents. To address this issue, corrosion inhibitors are widely used in the field of metal corrosion protection. While a wide variety of corrosion inhibitors exist in the prior art, most suffer from certain drawbacks. Traditional corrosion inhibitors, such as certain pyrimidine, indazole, and quinoline derivatives, while effective in inhibiting corrosion, are often difficult to degrade, causing environmental pollution, particularly the increasingly serious problem of water pollution. While these inhibitors contain a large number of heteroatoms (O, N, S) and aromatic ring structures, they effectively inhibit corrosion during use. However, their poor biodegradability imposes a long-term environmental burden. Furthermore, existing corrosion inhibitors often lack effective online monitoring methods during use. Traditional detection methods are not only time-consuming and labor-intensive, but also fail to accurately reflect the adsorption and concentration changes of the corrosion inhibitor on the metal surface. This makes it difficult to precisely control the amount of corrosion inhibitor added in practical applications, resulting in both resource waste and the failure to achieve the desired corrosion protection effect due to insufficient corrosion inhibitor. While common metal corrosion inhibitors currently on the market, such as certain organic and inorganic ones, can mitigate metal corrosion to a certain extent, their efficiency is generally low. According to existing literature, under optimal operating conditions, these inhibitors typically only achieve an efficiency of around 50%-60%, making them difficult to meet the needs of certain demanding industrial applications. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, the present invention provides a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, as well as its preparation method and application. A five-membered ring furan is introduced into the fluorophore coumarin through a simple and efficient Schiff base reaction. The Schiff base carbon-nitrogen double bond and furan heterocycle, as well as the oxygen heteroatom of the fluorophore coumarin itself, are utilized to coordinate well with iron ions. This not only achieves metal corrosion inhibition, but also makes it possible to detect the amount of corrosion inhibitor used by fluorescence, avoiding environmental pollution caused by excessive use. The fluorescent metal corrosion inhibitor is 7×10 -5 mol / L, it exhibits the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%.

[0004] The above-mentioned object of the present invention is achieved through the following technical solutions:

[0005] A fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, named CR-O, has the following specific structural formula:

[0006]

[0007] The preparation method of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle comprises the following steps: 4-diethylamino salicylaldehyde, diethyl malonate and piperidine are mixed in anhydrous ethanol, and the mixture is stirred and refluxed to obtain a crude product coumarin ester CR1; the coumarin ester CR1 is dissolved in an ethanol solution, hydrazine hydrate is slowly added dropwise, the reaction solution is stirred at room temperature, and the precipitated solid is filtered under reduced pressure to obtain a crude product CR2; CR2 and aldehyde are mixed with ethanol as a solvent to obtain a mixed solution, the solution is heated to reflux, the reaction solution is cooled at room temperature, and the solvent is removed by vacuum filtration to obtain a yellow powder fluorescent metal corrosion inhibitor CR-O; the specific reaction route is as follows:

[0008]

[0009] The preparation method of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle has the following specific steps:

[0010] S1. 10 mmol of 4-diethylaminosalicylaldehyde, diethyl malonate, and 4-6 ml of piperidine were mixed in 120-150 ml of anhydrous ethanol to obtain a mixture, and the mixture was stirred and refluxed to obtain compound CR1;

[0011] S2. 0.70 mmol of compound CR1 is further dissolved in 60-80 ml of ethanol solution, 3-5 ml of hydrazine hydrate is slowly added dropwise, and the reaction solution is stirred to obtain compound CR2;

[0012] S3.1.82mmol of compound CR2 and aldehyde are prepared with ethanol as solvent; the prepared mixed solution is heated to reflux at 80-85℃ for 2 hours, the reaction solution is cooled to 25℃ and filtered to obtain fluorescent metal corrosion inhibitor CR-O.

[0013] Furthermore, in step S1, the molar ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:2-3.

[0014] Furthermore, in step S1, the mixed solution is stirred and refluxed for 6 hours.

[0015] Furthermore, in step S2, the reaction solution was stirred at 25° C. for 30 min.

[0016] Furthermore, in step S3, the aldehyde is furfural.

[0017] Furthermore, in step S3, the molar ratio of compound CR2 to is 1:1-1.5.

[0018] The present invention also claims the use of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle prepared by the above preparation method in slow-release metal materials, specifically in slow-release applications on carbon steel. The application conditions are: the fluorescent metal corrosion inhibitor is at a temperature of 30°C, the corrosion inhibition time is 8 hours, and the fluorescent metal corrosion inhibitor concentration is 7×10 -5 mol / L, it inhibits corrosion of low carbon steel.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] The preparation method provided by the present invention not only retains the fluorescence properties of coumarin, but also introduces the active site of furan heterocycle, thereby enhancing the interaction between the corrosion inhibitor and the metal surface. Compound CR-O has excellent fluorescence properties, which makes it possible to monitor the distribution and concentration of the corrosion inhibitor on the metal surface in real time through fluorescence detection. Compared with traditional corrosion inhibitors, this fluorescence monitoring method is more intuitive and accurate, which helps to optimize the amount of corrosion inhibitor used and avoid waste and potential problems caused by excessive use. At the same time, due to its efficient corrosion inhibition performance, it can reduce corrosion to metals, thereby extending the service life of metal equipment and reducing resource waste and environmental pollution caused by corrosion. Compound CR-O is not only suitable for the corrosion protection of common metal materials such as carbon steel, but may also be extended to the corrosion protection field of other metal materials. The results of weight loss experiments show that at a temperature of 30°C, a corrosion inhibition time of 8 hours, and a corrosion inhibition concentration of 7×10 -5 mol / L, it exhibits the best corrosion inhibition effect on carbon steel, and the corrosion inhibition efficiency can reach 73.25%. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the H NMR spectrum of compound CR-O in Example 1 of the present invention in DMSO;

[0022] Figure 2 is the carbon NMR spectrum of compound CR-O in Example 1 of the present invention in DMSO;

[0023] Figure 3 This is a diagram of the weight loss method experimental device in Example 4 of the present invention;

[0024] Figure 4 This is a time-corrosion inhibition efficiency diagram in comparative examples 1 to 7 of the present invention;

[0025] Figure 5 This is a temperature-corrosion inhibition efficiency diagram in comparative examples 4, 8 to 11 of the present invention;

[0026] Figure 6 This is a graph showing the concentration-corrosion inhibition efficiency in comparative examples 8, 12 to 15 of the present invention;

[0027] Figure 3Middle: 1. Specimen fixing and hanging device, 2. Constant temperature water bath, 3. Beaker, 4. Low carbon steel sheet. DETAILED DESCRIPTION

[0028] The present invention is described in detail below by specific examples, but the scope of protection of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0029] The preparation method provided by the present invention not only retains the fluorescent properties of coumarin but also introduces active sites of furan heterocycles, enhancing the interaction between the corrosion inhibitor and the metal surface. Its highly effective corrosion inhibition can reduce metal corrosion, thereby extending the service life of metal equipment and reducing resource waste and environmental pollution caused by corrosion.

[0030] Example 1

[0031] Preparation method of fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle;

[0032] Step 1: Synthesis of Compound CR1

[0033]

[0034] Synthesis of Compound CR1: 4-Diethylaminosalicylaldehyde (10 g, 10 mmol), diethyl malonate (16 g, 20 mmol), and piperidine (5 mL) were mixed in anhydrous ethanol (150 mL). The mixture was stirred and refluxed for 6 hours. Thin-layer chromatography (TLC) was used to confirm the completion of the reaction. The reaction mixture was cooled to 25°C at room temperature and then poured into 100 mL of ice water. The precipitate was filtered, washed with water, dried, and recrystallized from toluene to obtain 7.9 g of a yellow crystalline solid (yield 52.83%).

[0035] Step 2: Synthesis of Compound CR2

[0036]

[0037] Synthesis of compound CR2: Coumarin ester CR1 (4 g, 0.70 mmol) was dissolved in 60 ml of ethanol solution, and 4 ml of hydrazine hydrate was slowly added dropwise. The reaction solution was stirred at 25°C for 30 min. The precipitated solid was filtered under reduced pressure to obtain a yellow solid powder (0.62 mmol, 3.6 g) with a yield of 94.59%. The crude product was used directly in the next reaction without purification.

[0038] Step 3: Synthesis of compound CR-O

[0039]

[0040] Synthesis of Compound CR-O: A solution of compound CR2 (500 mg, 1.82 mmol) and aldehyde (2.73 mmol) in ethanol was heated at 80°C for 2 hours. After TLC confirmed the completion of the reaction, the reaction solution was cooled to room temperature. The precipitated solid was filtered under reduced pressure to obtain 0.3148 g of a yellow powder, a fluorescent metal corrosion inhibitor, in a yield of 47.70%.

[0041] 1 H-NMR (500MHz, DMSO-d6): δ (ppm) 11.66 (s, 1H, O = C-NH-), 8.75 (s, 1H, = CH-), 8.36 (s, 1H, -N = CH-), 7.87 (s, 1H ,-ArH),(d,1H,J=9Hz,-ArH),6.90(s,1H,-ArH),6.78(d,1H,J=11.73Hz,=CH-O-),6.65(m,2H,=CH-CH=CH-O- ),3.50(q,4H,J=7Hz,`-N-CH2-),1.15(t,6H,J=6.9Hz,-CH2CH3).13C-NMR(125MHz,DMSOd6):δ(ppm)161.9,1 59.5,157.9,153.2,149.8,149.0,145.8,138.5,132.3,114.5,112.7,110.8,108.9,108.3,96.4,44.9,12.8.

[0042] Application Example 1

[0043] The fluorescent metal corrosion inhibitor CR-O prepared in Example 1 was prepared with 1 mol / L hydrochloric acid solution to a concentration of 7×10 -5 mol / L fluorescent metal corrosion inhibitor; soak the low-carbon steel sheet in a hydrochloric acid system containing the fluorescent metal corrosion inhibitor, the hydrochloric acid system is 1 mol / L. The low-carbon steel sheet is slow-released under the conditions of temperature 30°C and corrosion inhibition time of 8 hours.

[0044] Comparative Application Example 1

[0045] At a temperature of 25°C, the inhibition time is 2 hours, and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0046] Application Comparative Example 2

[0047] At a temperature of 25°C, the inhibition time is 4 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0048] Application Comparative Example 3

[0049] At a temperature of 25°C, the inhibition time is 6 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0050] Comparative Application Example 4

[0051] At a temperature of 25°C, the inhibition time is 8 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0052] Application Comparative Example 5

[0053] At a temperature of 25°C, the inhibition time is 10 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0054] Application Comparative Example 6

[0055] At a temperature of 25°C, the corrosion inhibition time is 24 hours, and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0056] Application Comparative Example 7

[0057] No fluorescent metal corrosion inhibitor is added, and other aspects are the same as those in Application Example 1.

[0058] Comparative Application Example 8

[0059] At a temperature of 30°C, the corrosion inhibition time is 8 hours and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0060] Comparative Application Example 9

[0061] At a temperature of 35°C, the inhibition time is 8 hours and the concentration of fluorescent metal inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0062] Comparative Application Example 10

[0063] At a temperature of 40 °C, the corrosion inhibition time is 8 hours and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0064] Comparative Application Example 11

[0065] At a temperature of 45°C, the corrosion inhibition time is 8 hours and the concentration of fluorescent metal corrosion inhibitor is 9×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0066] Application Comparative Example 12

[0067] At a temperature of 30°C, the corrosion inhibition time is 8 hours and the concentration of fluorescent metal corrosion inhibitor is 7×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0068] Comparative Application Example 13

[0069] At a temperature of 30°C, the corrosion inhibition time is 8 hours, and the concentration of fluorescent metal corrosion inhibitor is 5×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0070] Application Comparative Example 14

[0071] At a temperature of 30°C, the inhibition time is 8 hours, and the concentration of fluorescent metal inhibitor is 3×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0072] Application Comparative Example 15

[0073] At a temperature of 30°C, the corrosion inhibition time is 8 hours, and the concentration of fluorescent metal corrosion inhibitor is 1×10 -5 mol / L under the conditions of sustained release on low carbon steel sheet. Other aspects are the same as those in Application Example 1.

[0074] Applied experimental research: weight loss testing

[0075] The present invention uses weight loss experiments to test the corrosion inhibition effect of CR-O (application examples and comparative examples). The corrosion environment selected for the experiments is a 1 mol / L hydrochloric acid solution. To eliminate the influence of other factors, 20# low-carbon steel (carbon content 0.17-0.24%) is used for the experiments. The weight change of the low-carbon steel sheet after the experiment is measured in three groups and the average value is taken. The experiments are conducted in a constant temperature environment. Beakers are placed in a constant temperature water bath to maintain the temperature.

[0076] Treatment method for rusty low carbon steel sheets:

[0077] (1) First, scrub the mild steel specimen with absorbent cotton in deionized water, and then rinse the specimen with deionized water;

[0078] (2) Use absorbent cotton to clean the mild steel test pieces twice in anhydrous ethanol, using approximately 50 ml per 10 pieces.

[0079] (3) Use a hair dryer to dry the undried anhydrous ethanol on the test piece;

[0080] (4) In this experiment, 400, 600, and 1000 grade water sandpaper was used to polish the surface of the mild steel specimen;

[0081] (5) Rinse the polished low-carbon steel sheet with anhydrous ethanol and deionized water, and then dry it with a hair dryer;

[0082] (6) Spread the treated low-carbon steel sheet flat on the filter paper and wrap it. After drying in a dryer, it can be weighed and used.

[0083] In the attached Figure 3 After the weight loss experiment is completed, the mild steel sheet is removed, dried with a hair dryer, and weighed. The weighed mild steel sheet is then processed according to the same steps before other experiments. After the experiment is completed, the corrosion inhibition efficiency should be calculated.

[0084] The corrosion inhibition efficiency IE can be calculated by the following formula:

[0085]

[0086] W- is the average weight loss when adding corrosion inhibitor. W0- is the average weight loss when not adding corrosion inhibitor

[0087] By the attached Figure 4 The results show that the highest corrosion inhibition efficiency is 70.25% at 8 hours, which is the best corrosion protection performance for low-carbon steel sheets. The slow-release efficiency shows an upward trend from 2 hours to 8 hours, and begins to decline after 8 hours, with 8 hours being the time when the slow-release efficiency is the highest. The reason for this phenomenon may be that the corrosion inhibitor is continuously adsorbed by the low-carbon steel sheet before 8 hours, but at 8 hours, the surface of the low-carbon steel sheet has been saturated with adsorption. Even if time continues to increase, the corrosion inhibitor on the surface of the low-carbon steel sheet will no longer continue to increase, maintaining a certain stability. As time continues to increase, the low-carbon steel sheet will continue to corrode, the adsorption film on the surface will also be destroyed, and the corrosion inhibition efficiency will also decrease accordingly.

[0088] By the attached Figure 5 As shown, the highest corrosion inhibition efficiency, 72.29%, is achieved at 30°C, demonstrating the best corrosion protection for mild steel. However, as the temperature rises, the corrosion inhibition efficiency decreases. This is because rising temperature reduces the intermolecular forces, intensifying the thermal motion of corrosive particles in the acidic system and molecules on the metal surface. This significantly weakens the adsorption of the corrosion inhibitor on the mild steel surface, significantly reducing the corrosion inhibition efficiency as the temperature rises.

[0089] Attachment Figure 6 It is shown that when the corrosion inhibitor concentration is 7x10 -5mol / L, the highest corrosion inhibition efficiency was 73.25%, demonstrating the best corrosion protection for #20 mild steel. Furthermore, as the inhibitor concentration decreased, the inhibition efficiency also began to decline. This phenomenon occurs because as the inhibitor concentration decreases, the inhibitor factor added to the hydrochloric acid system also decreases. Under the same conditions, the amount of anti-corrosion factor that can be adsorbed by the #20 mild steel also decreases, resulting in a decrease in corrosion inhibition efficiency.

[0090] By analyzing the spectrum of CR-O and conducting weight loss experiments, we can obtain the basic anti-corrosion performance of CR-O. This can solve the problem of controlling the amount of corrosion inhibitor used. The experimental results show that the metal corrosion inhibitor based on coumarin and furan heterocycle has a good corrosion resistance at a temperature of 30°C, a service time of 8 hours and a concentration of 7x10 -5 mol / L has the best corrosion inhibition efficiency for 20# low carbon steel with carbon content (0.17~0.24%), which can more effectively prevent corrosion.

[0091] The above-described embodiments are only preferred embodiments of the present invention, and are not intended to be all feasible embodiments of the present invention. Any obvious modifications made by a person skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle, characterized in that the fluorescent The metal corrosion inhibitor is named CR-O, and its specific structural formula is as follows: .

2. Use of the fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as claimed in claim 1 in corrosion inhibition of metal materials.

3. A method for preparing a fluorescent metal corrosion inhibitor based on coumarin and furan heterocycle as claimed in claim 1, characterized in that, 4-Diethylaminosalicylaldehyde, diethyl malonate and piperidine are mixed in anhydrous ethanol, and the mixture is stirred and refluxed to obtain a crude product coumarin ester CR1; coumarin ester CR1 is dissolved in an ethanol solution, hydrazine hydrate is slowly added dropwise, the reaction solution is stirred at room temperature, and the precipitated solid is filtered under reduced pressure to obtain a crude product CR2; CR2 and aldehyde are mixed with ethanol as a solvent to obtain a mixed solution, the solution is heated to reflux, the reaction solution is cooled at room temperature, and the solvent is removed by vacuum filtration to obtain a yellow powder fluorescent metal corrosion inhibitor CR-O; the specific reaction route is as follows: 。 4. The preparation method according to claim 3, wherein: The specific steps are as follows: S1. 10 mmol of 4-diethylaminosalicylaldehyde, diethyl malonate, and 4-6 ml of piperidine were mixed in 120-150 ml of anhydrous ethanol to obtain a mixture, which was stirred and refluxed to obtain compound CR1; S2. 0.70 mmol of compound CR1 was further dissolved in 60-80 ml of ethanol solution, and 3-5 ml of hydrazine hydrate was slowly added dropwise. The reaction solution was stirred to obtain compound CR2; S3. 1.82 mmol of compound CR2 and aldehyde were prepared in ethanol as a solvent; the resulting mixed solution was heated to reflux at 80–85°C for 2 hours. The reaction solution was then cooled to 25°C and filtered to obtain the fluorescent metal corrosion inhibitor CR-O.

5. The preparation method according to claim 4, characterized in that: In step S1, the molar ratio of 4-diethylaminosalicylaldehyde to diethyl malonate is 1:2-3.

6. The preparation method according to claim 4, wherein: In step S1, the mixed solution is stirred and refluxed for 6 hours.

7. The preparation method according to claim 4, wherein: In step S2, the reaction solution was stirred at 25°C for 30 min.

8. The preparation method according to claim 4, wherein: In step S2 and step S3, the aldehyde is furfural.

9. The preparation method according to claim 4, wherein: In step S3, the molar ratio of compound CR2 to aldehyde is 1:1-1.5.

Images