Tryptophan-based polymer carbon dot corrosion inhibitor as well as preparation method and application thereof

Abstract

The invention provides a tryptophan-based polymer carbon dot corrosion inhibitor as well as a preparation method and application thereof, and relates to the technical field of carbon quantum dot corrosion inhibitors. The tryptophan-based polymer carbon dot corrosion inhibitor is prepared by the following steps: taking tryptophan and phenylalanine as reaction precursors, enabling molecules of the reaction precursors to be subjected to condensation reaction through solvothermal reaction, and then dialyzing and freeze-drying to obtain the tryptophan-based polymer carbon dot corrosion inhibitor. The tryptophan-based polymer carbon dot corrosion inhibitor prepared by adopting the technical scheme of the invention can interact with metal ions to form an adsorption film on the surface of metal so as to effectively inhibit the corrosion of the metal in an acid medium, and has the advantages of high corrosion inhibition efficiency, simple synthesis method, low cost, greenness, environmental protection and the like; and the corrosion inhibitor is suitable for large-scale popularization and application, and especially, the corrosion inhibition efficiency can reach 96% at most in an acidic environment with the pH value of 0.

Description

Technical Field

[0001] The present invention belongs to the technical field of corrosion inhibitors, and in particular relates to a tryptophan-based polymer carbon dot corrosion inhibitor, a preparation method thereof, and an application thereof. Background Art

[0002] With the acceleration of industrial production, metal materials have been widely used in various fields. However, metal materials inevitably corrode during use, leading to performance degradation and seriously affecting the safety and reliable service of mechanical devices, instruments and equipment, work platforms, metal pipelines, etc. based on them. Pickling is a common method for removing dirt and rust from metal surfaces. However, during the pickling process, the pickling solution is highly corrosive, inevitably causing over-corrosion of the metal surface. In addition, the hydrogen produced by the reaction with the metal not only causes hydrogen embrittlement corrosion of the metal material, but also produces a large amount of acid mist, which deteriorates the service environment.

[0003] In order to reduce the corrosion loss of metals during the pickling process, adding corrosion inhibitors to the pickling solution is the most widely used and effective method. Traditional corrosion inhibitors mainly include inorganic corrosion inhibitors and organic corrosion inhibitors. Among them, inorganic corrosion inhibitors are mainly composed of certain acid anions and metal cations. Organic corrosion inhibitors such as azoles, quinolines, thiophenes and Mannich bases, etc., but due to their shortcomings such as strong toxicity, low water solubility, and difficulty in degradation, they cause serious harm to human health and the ecological environment. With the improvement of people's environmental awareness, the development of a low-cost, highly water-soluble, environmentally friendly and efficient corrosion inhibitor for metal corrosion protection during the pickling process has become the main development trend of corrosion inhibitor research.

[0004] As one of the carbon nanomaterials, carbon quantum dots (Cd) have high water solubility, excellent fluorescence and optical properties, good biocompatibility, low toxicity, low cost and other characteristics, and have been widely used in the fields of photoelectric sensors and cell imaging. In addition, the rich functional groups and large specific surface area on the surface of carbon quantum dots make them have a large number of active sites, which can coordinate with metals, making them show great potential in metal corrosion inhibition. For example, Chinese invention patent CN117446785A discloses a preparation method and application of a carbon quantum dot corrosion inhibitor, which comprises mixing chitosan, amino acids and water to obtain a mixed solution, irradiating the mixed solution with a high-energy laser pulse, so that a high temperature and high pressure state is locally generated in the mixed solution, thereby converting the chitosan in the solution into carbon quantum dots, and at the same time, reacting with the functional groups in chitosan and amino acids (such as -NH2 of chitosan and -COOH in amino acids) to obtain nitrogen-doped carbon quantum dots. This method uses high-energy laser pulse irradiation to react and obtain a carbon quantum dot corrosion inhibitor, which has good corrosion inhibition performance for carbon steel in 0.5M hydrochloric acid (pH ~ 3), with a corrosion inhibition efficiency of up to 97.4%; however, under higher acidity environmental conditions (such as pH ~ 0), the corrosion inhibition effect of the carbon quantum dot corrosion inhibitor is not good.

[0005] Based on the existing technology, the present invention adopts a solvent thermal method to prepare a polymer carbon dot corrosion inhibitor, which can be used to inhibit the corrosion effect of metal pickling process (pH ~ 0). Its synthesis method is simple, the conditions are mild, and the cost is low, which is suitable for large-scale promotion and application. Summary of the Invention

[0006] The present invention aims to provide a tryptophan-based polymer carbon dot corrosion inhibitor and its preparation method and application, which has good water solubility and excellent corrosion inhibition performance and can effectively inhibit the corrosion of metal materials in a strong acidic environment.

[0007] As one of the objects of the invention, the present invention provides a method for preparing a tryptophan-based polymer carbon dot corrosion inhibitor, comprising using tryptophan and phenylalanine as reaction precursors, causing a condensation reaction between the molecules of the reaction precursors through a solvent thermal reaction, and obtaining the tryptophan-based polymer carbon dot corrosion inhibitor after post-treatment.

[0008] In some specific embodiments, tryptophan is L-tryptophan; and phenylalanine is L-phenylalanine.

[0009] In some specific embodiments, the mass ratio of tryptophan to phenylalanine is (1-4):1 or 1:(1-4).

[0010] In some specific embodiments, the particle size of the tryptophan-based polymer carbon dot corrosion inhibitor is 5 to 10 nm.

[0011] In some specific embodiments, the solvothermal reaction includes uniformly mixing the reaction precursor with a solvent and then performing the reaction.

[0012] In some specific embodiments, the solvent is water and / or ethanol.

[0013] In some specific embodiments, the conditions of the solvothermal reaction include: a reaction temperature of 150 to 250° C., and a reaction time of 5 to 15 hours.

[0014] In some specific embodiments, the post-treatment includes purifying and drying the condensation product.

[0015] Preferably, the purification comprises cooling the condensation product to room temperature and then dialyzing it in a dialysis bag with a molecular weight cut-off of 1.0 to 3.0 kDa, the dialysis time being 12 to 24 hours.

[0016] Preferably, the drying method comprises vacuum freeze drying.

[0017] Preferably, the drying time is 24 to 48 hours, and the drying temperature is -70 to -90°C.

[0018] As one aspect of the invention, the present invention also provides a tryptophan-based polymer carbon dot corrosion inhibitor, which is prepared using the above-mentioned preparation method.

[0019] As one aspect of the invention, the present invention also provides the use of the aforementioned tryptophan-based polymer carbon dot corrosion inhibitor in the corrosion protection of metal materials in an acidic environment.

[0020] The tryptophan-based polymer carbon dot corrosion inhibitor prepared by the present invention can be used for metal corrosion protection. The tryptophan-based polymer carbon dots prepared by the solvent thermal method interact with the carbon steel surface to form an adsorption layer on the carbon steel surface, thereby slowing down the corrosion of the metal.

[0021] Preferably, the metal material includes any one of carbon steel, copper, aluminum and other alloys.

[0022] Preferably, the acidic conditions include: hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, phosphoric acid solution with a pH of 0.

[0023] Preferably, the concentration of the tryptophan-based polymer carbon dot corrosion inhibitor is 50 to 200 mg·L -1 .

[0024] The beneficial technical effects obtained by the present invention are:

[0025] 1. Using the technical solution of the present invention, tryptophan and / or phenylalanine are used as precursors or undergo a solvothermal reaction to obtain polymer carbon dots. The polymer carbon dots can interact with the surface of carbon steel, forming an adsorption layer on the surface of the metal material, thereby reducing the corrosion of the metal. At the same time, after the polymer film is formed on the surface of the metal material, the benzene rings in the tryptophan and phenylalanine molecular structures form a π-π conjugation effect, which can further enhance the corrosion inhibition of the metal.

[0026] 2. The tryptophan-based polymer carbon dot corrosion inhibitor prepared by the technical solution of the present invention is composed of four elements: C, N, O, and H. Compared with the existing technology, the carbon quantum dots are doped with more nitrogen (N) elements, which effectively inhibits the corrosion of metals in acidic media by forming an adsorption film on the metal surface. It also has the characteristics of fluorescent response, high corrosion inhibition efficiency, and easy solubility in acid.

[0027] 3. The reaction precursor of the tryptophan-based polymer carbon dots provided by the present invention is a biological amino acid, which has the advantages of low cost and environmental protection. In particular, the solvent thermal reaction is mild and simple to operate, which is suitable for large-scale promotion and application.

[0028] 4. The tryptophan-based polymer carbon dot corrosion inhibitor provided by the present invention has good water solubility and excellent corrosion inhibition performance. In an acidic environment, the concentration is 200 mg·L -1 When the temperature is 200000 °C, the corrosion inhibition efficiency is as high as 96.04%, which can effectively inhibit the corrosion of carbon steel in acid solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1a This is the Nyquist plot of carbon steel in Comparative Example 1 of the present invention after being immersed in 1M HCl solution for 1 hour.

[0030] Figure 1b This is the polarization curve of carbon steel in Comparative Example 1 of the present invention after being immersed in 1M HCl solution for 1 hour.

[0031] Figure 2 This is a graph showing the change in corrosion rate of carbon steel during immersion in 1M HCl solution for 72 hours as a function of immersion time in Comparative Example 1 of the present invention.

[0032] Figure 3a The carbon steel in Comparative Examples 2 and 3 of the present invention contains 200 mg·L -1 Nyquist plot of L-tryptophan / L-phenylalanine after immersion in 1M HCl solution for 1 h.

[0033] Figure 3b The carbon steel in Comparative Examples 2 and 3 of the present invention contains 200 mg·L -1 Polarization curves of L-tryptophan and L-phenylalanine after immersion in 1 M HCl solution for 1 h.

[0034] Figure 4a The carbon steel in comparative example 2 of the present invention contains 200 mg.L -1 Corrosion rate versus immersion time during immersion in 1 M HCl solution of L-tryptophan for 72 h.

[0035] Figure 4b The carbon steel in comparative example 2 of the present invention contains 200 mg·L -1 Corrosion inhibition efficiency of L-tryptophan in 1M HCl solution during immersion for 72 hours as a function of immersion time.

[0036] Figure 5a The carbon steel in comparative example 3 of the present invention contains 200 mg·L -1 Corrosion rate of carbon steel in 1M HCl solution of L-phenylalanine changes with immersion time during 72h immersion.

[0037] Figure 5b The carbon steel in comparative example 3 of the present invention contains 200 mg·L -1 Corrosion inhibition efficiency of L-phenylalanine in 1M HCl solution during immersion for 72 hours as a function of immersion time.

[0038] Figure 6a This is the Nyquist plot of carbon steel in Comparative Example 4 of the present invention after being immersed in a 1M HCl solution containing different concentrations of phenylalanine-based polymer carbon dot corrosion inhibitor for 1 hour.

[0039] Figure 6b 1 is the polarization curve of carbon steel in comparative example 4 of the present invention after being immersed in 1M HCl solution containing different concentrations of phenylalanine-based polymer carbon dot corrosion inhibitor for 1 hour.

[0040] Figure 7a This is the Nyquist plot of carbon steel in Comparative Example 5 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0041] Figure 7b 1 is the polarization curve of carbon steel in comparative example 5 of the present invention after being immersed in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0042] Figure 8a 1 is the Nyquist plot of the carbon steel in Example 1 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0043] Figure 8b 1 is the polarization curve of the carbon steel in Example 1 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0044] Figure 9a This is a graph showing the change in corrosion rate versus immersion time of carbon steel in Example 1 of the present invention during immersion in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 72 hours.

[0045] Figure 9b This is a graph showing the change in corrosion inhibition efficiency versus immersion time of carbon steel in Example 1 of the present invention during immersion in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 72 hours.

[0046] Figure 10a This is the Nyquist plot of carbon steel in Example 2 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0047] Figure 10b 1 is the polarization curve of the carbon steel in Example 2 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0048] Figure 11a This is a graph showing the change in corrosion rate of carbon steel as a function of immersion time during immersion in a 1 M HCl solution containing tryptophan-based polymer carbon dot corrosion inhibitors at different concentrations for 72 h in Example 2 of the present invention.

[0049] Figure 11b This is a graph showing the change in corrosion inhibition efficiency of carbon steel as a function of immersion time during immersion in a 1 M HCl solution containing tryptophan-based polymer carbon dot corrosion inhibitors at different concentrations for 72 hours in Example 2 of the present invention.

[0050] Figure 12a This is the Nyquist plot of carbon steel in Example 3 of the present invention after being immersed in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0051] Figure 12b 3 are polarization curves of carbon steel in Example 3 of the present invention after being immersed in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 1 hour.

[0052] Figure 13a This is a graph showing the change in corrosion rate versus immersion time of carbon steel in Example 3 of the present invention during immersion in a 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor for 72 hours.

[0053] Figure 13b This is a graph showing the change in corrosion inhibition efficiency of carbon steel as a function of immersion time during immersion in a 1M HCl solution containing tryptophan-based polymer carbon dot corrosion inhibitors at different concentrations for 72 hours in Example 3 of the present invention.

[0054] Figure 14The graphs are Fourier transform infrared (FT-IR) spectra of the tryptophan-based polymer carbon dot corrosion inhibitor prepared from tryptophan and phenylalanine in different ratios according to the present invention.

[0055] Figure 15a This is a TEM image of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in Example 1 of the present invention.

[0056] Figure 15b This is the HRTEM image of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0057] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0058] A preparation method for a tryptophan-based polymer carbon dot corrosion inhibitor comprises the following steps: using tryptophan and phenylalanine as reaction precursors, adding them to water, adjusting the pH value of the solution with HCl until all solids are dissolved, then adding them to a PTFE reactor, carrying out a hydrothermal reaction in a drying oven, cooling to room temperature after the reaction is completed, removing large particles of solid from the obtained solution by centrifugation, purifying the supernatant by dialysis, and finally drying the dialyzate by vacuum freeze-drying to obtain tryptophan-based polymer carbon dot corrosion inhibitor powder.

[0059] Furthermore, the reaction precursor is a combination of tryptophan and phenylalanine.

[0060] Furthermore, the reaction precursors are tryptophan and phenylalanine, and the mass ratio is (0-4):1 or 1:(0-4).

[0061] Furthermore, the volume of the solvent is 30 to 80 mL.

[0062] Furthermore, the temperature of the solvent thermal reaction is 150-250° C., and the time is 5-15 hours.

[0063] Furthermore, the dialysis time is 12 to 24 hours.

[0064] Furthermore, the drying temperature is -70 to -90°C, and the drying time is 36 to 72 hours.

[0065] The present invention provides a tryptophan-based polymer carbon dot corrosion inhibitor prepared by the above-mentioned preparation method. The corrosion inhibitor has good water solubility and high corrosion inhibition efficiency.

[0066] The present invention provides application of the above-mentioned tryptophan-based polymer carbon dot corrosion inhibitor in the field of metal corrosion protection.

[0067] The principle of the tryptophan-based polymer carbon dot corrosion inhibitor prepared by the present invention for metal corrosion protection is that the tryptophan-based polymer carbon dots prepared by the solvent thermal method interact with the carbon steel surface to form an adsorption layer on the carbon steel surface, thereby slowing down the corrosion of the metal.

[0068] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0069] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0070] Example 1

[0071] This embodiment provides a method for preparing a tryptophan-based polymer carbon dot corrosion inhibitor, and the specific preparation steps include:

[0072] (1) Preparation of tryptophan-based polymer carbon dot corrosion inhibitor: 1.02 g L-tryptophan and 1.66 g L-phenylalanine were dissolved in 40 mL of deionized water, and an appropriate amount of hydrochloric acid (5-15 mL) was added. The mixture was ultrasonically dissolved until completely dissolved. Deionized water was then added to 60 mL, and the mixture was added to a PTFE-lined autoclave and heated at 200°C for 8 h. After the reaction was completed and cooled to room temperature, the reaction solution was centrifuged to remove large particles, and the supernatant was placed in a 1.0 kDa dialysis bag and dialyzed for 12 h for purification. The purified solution was vacuum freeze-dried for 48-72 h to obtain a tryptophan-based polymer carbon dot corrosion inhibitor.

[0073] (2) Corrosion inhibition performance evaluation test: A Q235 carbon steel substrate was immersed in a 1M HCl (pH 0) solution, and different masses of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example were added to adjust the corrosion inhibitor concentration to 50 mg·L -1 , 100mg·L -1 , 200mg·L -1 After immersion at room temperature for 1 hour, electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed. The results are shown in Figure 8a and Figure 8b Furthermore, a carbon steel substrate (1cm*1cm*2mm) was immersed in a 1M HCl solution containing tryptophan-based polymer carbon dots at different concentrations. The substrate was taken out several times during the 72h immersion period, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate and corrosion inhibition efficiency of the carbon steel in 1M HCl containing different concentrations of the tryptophan-based polymer carbon dots corrosion inhibitor prepared in this example were calculated. The results are shown in Figure 9a and Figure 9b.

[0074] Figure 8a and Figure 8b The Nyquist curve and polarization curve of carbon steel after immersion in 1M HCl solution containing the tryptophan-based polymer carbon dot corrosion inhibitor of this embodiment for 1 hour are shown. The results show that as the concentration of the tryptophan-based polymer carbon dot corrosion inhibitor increases, the capacitance arc radius in the Nyquist curve increases, and the corrosion current density in the polarization curve decreases, indicating that the corrosion inhibition performance gradually improves. When the concentration of the tryptophan-based polymer carbon dot corrosion inhibitor is 200 mg·L -1 When the capacitive reactance arc radius is the largest, the charge transfer impedance is about 119.3Ω·cm 2 , the corrosion current density is 2.03×10 -4 A.cm -2 .

[0075] Figure 9a and Figure 9b The corrosion rate of carbon steel in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dots corrosion inhibitor (50 mg·mL -1 , 100mg·mL -1 , 200mg·mL -1 The corrosion rate and inhibition efficiency of carbon steel were analyzed during the immersion period of 72 h. The results showed that with the increase of inhibitor concentration, the corrosion rate of carbon steel slowed down and the inhibition efficiency increased. After immersion for 72 h, the corrosion rates were 6.68×10 -4 g·cm -2 ·h -1 , 4.52×10 -4 g·cm -2 ·h -1 , 3.36×10 -4 g·cm -2 ·h -1 The corrosion inhibition efficiencies are 30.49%, 53.00% and 65.07% respectively.

[0076] See also Figure 15a and Figure 15b , respectively, are TEM and HRTEM images of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example. As can be seen from the figures, the prepared carbon dot particles are approximately spherical and well dispersed, with an average particle size of approximately 4 nm. In addition, distinct lattice fringes can be seen in the figure, which are measured to be 0.29 nm, corresponding to the graphite (100) plane, indicating that the prepared carbon dots have a graphite-like structure.

[0077] Example 2

[0078] This embodiment provides a method for preparing a tryptophan-based polymer carbon dot corrosion inhibitor, and the specific preparation steps include:

[0079] (1) Preparation of tryptophan-based polymer carbon dot corrosion inhibitor: 1.02 g L-tryptophan and 0.83 g L-phenylalanine were dissolved in 40 mL of deionized water, and an appropriate amount of hydrochloric acid (5-15 mL) was added. The mixture was ultrasonically dissolved until completely dissolved. Deionized water was then added to 60 mL, and the mixture was added to a PTFE-lined autoclave and heated at 200°C for 8 h. After the reaction was completed and cooled to room temperature, the reaction solution was centrifuged to remove large particles, and the supernatant was placed in a 1.0 kDa dialysis bag and dialyzed for 12 h for purification. The purified solution was vacuum freeze-dried for 48-72 h to obtain a tryptophan-based polymer carbon dot corrosion inhibitor.

[0080] (2) Corrosion inhibition performance evaluation test: A Q235 carbon steel substrate was immersed in a 1M HCl solution, and different masses of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example were added to adjust the corrosion inhibitor concentration to 50 mg·L -1 , 100mg·L -1 , 200mg·L -1 After immersion at room temperature for 1 hour, electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed. Figure 10a and Figure 10b Furthermore, a carbon steel substrate (1cm*1cm*2mm) was immersed in a 1M HCl solution containing different concentrations of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example. The substrate was taken out several times during the 72h soaking period, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate and corrosion inhibition efficiency of the carbon steel in 1M HCl containing different concentrations of the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example were calculated. The results are shown in Figure 11a and 11b .

[0081] Figure 10a and Figure 10b Figure 2 shows the Nyquist curves and polarization curves of carbon steel after immersion in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example for 1 hour. The results show that as the concentration of tryptophan-based polymer carbon dot corrosion inhibitor increases, the capacitance arc radius in the Nyquist curve increases, and the corrosion current density in the polarization curve decreases, indicating that the corrosion inhibition performance gradually improves. When the corrosion inhibitor concentration is 200 mg·L -1 When the capacitive reactance arc radius is the largest, the charge transfer impedance is about 592Ω·cm 2 , the corrosion current density is 3.35×10 -5 A.cm -2 .

[0082] Figure 11a and Figure 11bThe curves of the corrosion rate and inhibition efficiency of carbon steel during immersion in a 1M HCl solution containing the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example for 72 hours show that as the concentration of the corrosion inhibitor increases, the corrosion rate of carbon steel slows down and the inhibition efficiency increases. After immersion for 72 hours, the corrosion rates are 3.31×10 -4 g·cm -2 ·h -1 , 9.46×10 -5 g·cm -2 ·h -1 , 3.81×10 -5 g·cm -2 ·h -1 The corrosion inhibition efficiencies are 65.58%, 90.15% and 96.04% respectively.

[0083] Example 3

[0084] This embodiment provides a method for preparing a tryptophan-based polymer carbon dot corrosion inhibitor, and the specific preparation steps include:

[0085] (1) Preparation of tryptophan-based polymer carbon dot corrosion inhibitor: 2.04 g L-tryptophan and 0.83 g L-phenylalanine were dissolved in 40 mL of deionized water, and an appropriate amount of hydrochloric acid (5-15 mL) was added. The mixture was ultrasonically dissolved until completely dissolved. Deionized water was then added to 60 mL, and the mixture was added to a PTFE-lined autoclave and heated at 200°C for 8 h. After the reaction was completed and cooled to room temperature, the reaction solution was centrifuged to remove large particles, and the supernatant was placed in a 1.0 kDa dialysis bag and dialyzed for 12 h for purification. The purified solution was vacuum freeze-dried for 48-72 h to obtain a tryptophan-based polymer carbon dot corrosion inhibitor.

[0086] (2) Corrosion inhibition performance evaluation test: The Q235 carbon steel substrate was immersed in a 1M HCl solution, and the tryptophan-based polymer carbon dot corrosion inhibitor prepared in this example was added to adjust the corrosion inhibitor concentration to 50 mg·L -1 , 100mg·L -1 , 200mg·L -1 After immersion at room temperature for 1 hour, electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed. The results are shown in Figure 12a and Figure 12b Furthermore, a carbon steel substrate (1 cm*1 cm*2 mm) was immersed in a 1 M HCl solution containing different concentrations of the tryptophan-based polymer carbon dots prepared in this example. The substrate was taken out several times during the immersion period of 7 to 2 hours, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate and corrosion inhibition efficiency of the carbon steel in 1 M HCl containing different concentrations of the tryptophan-based polymer carbon dots prepared in this example were calculated. Figure 13a and Figure 13b .

[0087] Figure 12a and Figure 12b Figure 2 shows the Nyquist curve and polarization curve of carbon steel after immersion in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor of this embodiment for 1 hour. The results show that as the concentration of tryptophan-based polymer carbon dot corrosion inhibitor increases, the capacitance arc radius in the Nyquist curve increases, and the corrosion current density in the polarization curve decreases, indicating that the corrosion inhibition performance gradually improves. When the corrosion inhibitor concentration is 200 mg·L -1 When the capacitive reactance arc radius is the largest, the charge transfer impedance is about 382.6Ω·cm 2 , the corrosion current density is 7.99×10 -5 A.cm -2 .

[0088] Figure 13a and Figure 13b The curves of the corrosion rate and inhibition efficiency of carbon steel during immersion in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dot corrosion inhibitor of this example for 72 hours show that as the concentration of the corrosion inhibitor increases, the corrosion rate of carbon steel slows down and the inhibition efficiency increases. After immersion for 72 hours, the corrosion rates are 4.88×10 -4 g·cm -2 ·h -1 , 1.95×10 -4 g·cm -2 ·h -1 , 6.44×10 -5 g·cm -2 ·h -1 The corrosion inhibition efficiencies are 49.25%, 79.72% and 93.30% respectively.

[0089] Figure 14 The FTIR spectra of the tryptophan-based polymer carbon dot corrosion inhibitors prepared in Examples 1 to 3 are shown in Figure 1. -1 The peaks at 1621 and 1583 cm-1 are derived from the stretching vibration of -C=O in -COOH. -1 The absorption peak at 1450 cm-1 proves the existence of amide I and amide II; -1 The absorption peak at 1000 cm is attributed to the C=C stretching mode of the aromatic domain, while the absorption peak at 1000 cm -1 The absorption peak at 800-900 cm is related to the stretching vibration of C-OH. -1 The absorption peak at corresponds to the bending vibration of aromatic CH. The FT-IR characteristics of the tryptophan-based polymer carbon dot corrosion inhibitors prepared in Examples 1 to 3 show that the prepared carbon dots have the basic structure of the raw materials.

[0090] Example 4

[0091] The difference between this embodiment and embodiment 1 is that in step (1), the mass of L-tryptophan is 8.16 g and the mass of L-phenylalanine is 1.66 g, and the molar ratio of L-tryptophan to L-phenylalanine is 4:1.

[0092] The other steps are the same.

[0093] Carbon steel was immersed in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dots corrosion inhibitor of this example for 72 hours. As the concentration of corrosion inhibitor increased, the corrosion rate of carbon steel slowed down and the corrosion inhibition efficiency increased. After immersion for 72 hours, the corrosion rate of carbon steel slowed down and the corrosion inhibition efficiency increased when the corrosion inhibitor concentration was 200 mg·L -1 The corrosion inhibition efficiency can reach more than 90%.

[0094] Example 5

[0095] The difference between this embodiment and embodiment 1 is that in step (1), the mass of L-tryptophan is 1.02 g and the mass of L-phenylalanine is 3.32 g, and the molar ratio of L-tryptophan to L-phenylalanine is 1:4.

[0096] The other steps are the same.

[0097] Carbon steel was immersed in 1M HCl solution containing different concentrations of tryptophan-based polymer carbon dots corrosion inhibitor of this example for 72 hours. As the concentration of corrosion inhibitor increased, the corrosion rate of carbon steel slowed down and the corrosion inhibition efficiency increased. After immersion for 72 hours, the corrosion rate of carbon steel slowed down and the corrosion inhibition efficiency increased when the corrosion inhibitor concentration was 200 mg·L -1 The corrosion inhibition efficiency can reach more than 80%.

[0098] Comparative Example 1

[0099] The polished Q235 carbon steel substrate was placed in acetone and anhydrous ethanol for ultrasonic cleaning in sequence to remove oil and pollutants on the surface, and then wiped dry with a non-woven cloth.

[0100] Carbon steel substrate (exposed area 1cm 2 ) as the working electrode, saturated calomel electrode as the reference electrode, and platinum sheet as the auxiliary electrode. Electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed in 1 M HCl solution. The results are shown in Figure 1a and Figure 1b .

[0101] Furthermore, a carbon steel substrate (1cm*1cm*2mm) was immersed in a 1M HCl solution. During the immersion period of 72h, the substrate was taken out several times, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate of the carbon steel in 1M HCl in this comparative example was calculated. The results are shown in Figure 2 .

[0102] like Figure 1a and Figure 1b As shown in Figure 2, the charge transfer impedance of carbon steel after immersion in blank 1M HCl solution for 1 hour is about 44.32Ω·cm 2 , the corrosion current density is 7.33×10 -4 A.cm -2 .

[0103] Figure 2 The corrosion rate of carbon steel in blank 1M HCl solution changes with immersion time. The results show that the corrosion rate of carbon steel during immersion decreases first and then increases with immersion time. The corrosion rate after immersion for 72 hours is about 9.61×10 -4 g·cm -2 ·h -1 .

[0104] Comparative Example 2

[0105] The polished Q235 carbon steel substrate was placed in acetone and anhydrous ethanol for ultrasonic cleaning in sequence to remove oil and pollutants on the surface, and then wiped dry with a non-woven cloth.

[0106] Carbon steel substrate (exposed area 1cm 2 ) as the working electrode, saturated calomel electrode as the reference electrode, platinum sheet as the auxiliary electrode, in the presence of 200 mg·L -1 Electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed in 1 M HCl solution of L-tryptophan. The results are shown in Figure 3a and Figure 3b .

[0107] Furthermore, a carbon steel substrate (1 cm*1 cm*2 mm) was immersed in a solution containing 200 mg·L -1 The samples were taken out from the 1M HCl solution of L-tryptophan several times during the 72h soaking period, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate and corrosion inhibition efficiency of L-tryptophan on carbon steel in 1M HCl in this comparative example were calculated. The results are shown in Figure 4a and Figure 4b .

[0108] like Figure 3a and Figure 3b As shown, carbon steel contains 200mg·L -1 The charge transfer impedance of L-tryptophan after immersion in 1M HCl solution for 1 hour is 41.24Ω·cm 2 , the corrosion current density is 7.25×10 -4 A.cm -2 . In the presence of 200mg·L -1During the immersion in 1M HCl solution of L-tryptophan, the corrosion rate of carbon steel showed a trend of first decreasing and then increasing, and the trend of corrosion inhibition efficiency showed a decreasing trend; after immersion for 72h, Figure 4a and 4b The corrosion rate of medium carbon steel is about 9.10×10 -4 g·cm -2 ·h -1 The corrosion inhibition efficiency was 5.28%. Compared with Example 1, this result shows that L-tryptophan has almost no corrosion inhibition effect on carbon steel.

[0109] Comparative Example 3

[0110] The polished Q235 carbon steel substrate was placed in acetone and anhydrous ethanol for ultrasonic cleaning to remove the oil and contaminants on the surface, and then wiped dry with non-woven cloth. 2 ) as the working electrode, saturated calomel electrode as the reference electrode, platinum sheet as the auxiliary electrode, in the presence of 200 mg·L -1 Electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed in 1 M HCl solution of L-phenylalanine. The corresponding results are shown in Figure 3a and Figure 3b .

[0111] Furthermore, a carbon steel substrate (1 cm*1 cm*2 mm) was immersed in a solution containing 200 mg·L -1 The samples were taken out from the 1M HCl solution of L-phenylalanine several times during the 72h soaking period, dried, and weighed. The weight was compared with the weight before corrosion. The corrosion rate and inhibition efficiency of L-phenylalanine on carbon steel in 1M HCl in this comparative example were calculated. The results are shown in Figure 5a and Figure 5b .

[0112] like Figure 3a and Figure 3b As shown, carbon steel contains 200mg·L -1 The charge transfer impedance of L-phenylalanine after immersion in 1M HCl solution for 1 hour is 47.18Ω·cm 2 , the corrosion current density is 6.04×10 -4 A.cm -2 Carbon steel containing 200mg·L -1 The corrosion rate of L-phenylalanine in 1M HCl solution showed a trend of decreasing first and then increasing, and the corrosion inhibition efficiency decreased first and then increased, and finally stabilized. Figure 5a and 5b The corrosion rate of carbon steel is 8.34×10 -4 g·cm -2 ·h -1The corrosion inhibition efficiency is 13.25%. Compared with Comparative Examples 1 and 2, the results show that L-phenylalanine has almost no corrosion inhibition efficiency on carbon steel.

[0113] Comparative Example 4

[0114] The difference between this comparative example and Example 1 is that in step (1), only 1.66 g of L-phenylalanine was added.

[0115] The Q235 carbon steel substrate was further immersed in a 1M HCl solution, and the carbon dot corrosion inhibitor prepared in this comparative example was added to adjust the corrosion inhibitor concentration to 50 mg·L -1 , 100mg·L -1 , 200mg·L -1 After immersion at room temperature for 1 hour, electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed. The results are shown in Figure 6a and Figure 6b .

[0116] Figure 6a and Figure 6b The Nyquist curves and polarization curves of carbon steel after being immersed in 1M HCl solution containing different concentrations of carbon dot corrosion inhibitor for 1 hour are shown. The results show that as the concentration of carbon dot corrosion inhibitor increases, the capacitive arc radius in the Nyquist curve increases, and the corrosion current density in the polarization curve decreases, indicating that the corrosion inhibition performance gradually improves. When the corrosion inhibitor concentration is 200 mg·L -1 When the capacitive reactance arc radius is the largest, the charge transfer impedance is about 112.0Ω·cm 2 , the corrosion current density is 3.17×10 -4 A.cm -2 .

[0117] Comparative Example 5

[0118] The difference between this comparative example and Example 1 is that in step (1), only 1.02 g of L-tryptophan was added.

[0119] The Q235 carbon steel substrate was further immersed in a 1M HCl solution, and the carbon dot corrosion inhibitor prepared in this comparative example was added to adjust the corrosion inhibitor concentration to 50 mg·L -1 , 100mg·L -1 , 200mg·L -1 After immersion at room temperature for 1 hour, electrochemical impedance spectroscopy and potentiodynamic polarization tests were performed. The results are shown in Figure 7a and Figure 7b , which are the Nyquist curves and polarization curves of carbon steel after being immersed in 1M HCl solution containing different concentrations of the carbon dot corrosion inhibitor of this comparative example for 1 hour.

[0120] Depend on Figure 7a and Figure 7b It can be seen that with the increase of the concentration of carbon dot corrosion inhibitor, the capacitance arc radius in the Nyquist curve increases, and the corrosion current density in the polarization curve decreases, indicating that the corrosion inhibition performance gradually improves. When the corrosion inhibitor concentration is 200 mg·L -1 When the capacitive reactance arc radius is the largest, the charge transfer impedance is about 497.8Ω·cm 2 , the corrosion current density is 4.95×10 -5 A.cm -2 .

[0121] Comparative Example 6

[0122] The difference between this embodiment and embodiment 1 is that in step (1), the mass of L-tryptophan is 10.2 g and the mass of L-phenylalanine is 1.66 g, and the molar ratio of L-tryptophan to L-phenylalanine is 5:1.

[0123] The other steps are the same.

[0124] Comparative Example 7

[0125] The difference between this embodiment and embodiment 1 is that in step (1), the mass of L-tryptophan is 1.02 g and the mass of L-phenylalanine is 4.15 g, and the molar ratio of L-phenylalanine to L-tryptophan is 5:1.

[0126] The other steps are the same.

[0127] Carbon steel was immersed in 1M HCl solutions of corrosion inhibitors of Comparative Example 6 and Comparative Example 7 with different concentrations. Compared with the embodiment, the corrosion rate of the carbon steel showed a trend of first decreasing and then increasing, and the trend of the corrosion inhibition efficiency showed a decreasing trend; however, after immersion for 72 hours, the corrosion rate of the carbon steel accelerated, and the corrosion inhibition effect was less than 80%, which did not meet the requirements of practical application.

[0128] Results analysis: Compared with Comparative Examples 1 to 7, the present invention embodiment has L-phenylalanine and L-tryptophan as tryptophan-based polymer carbon dots with a concentration of 200 mg·L -1 When the molar ratio of tryptophan to phenylalanine is (1-4): (1 or 0), it can exert an excellent corrosion inhibition effect. More preferably, when the molar ratio of tryptophan to phenylalanine is (1-2): 1 or 1:0, the effect is even better. Best, when the molar ratio of the two amino acids is 1:1, the corrosion inhibition efficiency is the best, which can reach more than 96%. When the molar ratio of tryptophan to phenylalanine is 5:1 (or 1:5), the corrosion inhibition effect is less than 80%, which can no longer meet the actual needs. In particular, when only L -When phenylalanine single amino acid self-polymerization was used to prepare polymer carbon dots, compared with blank hydrochloric acid solution, the results showed that there was almost no corrosion inhibition effect.

[0129] The above embodiments are described to facilitate those skilled in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply them to the invention.

[0130] The general principles described herein can be applied to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a tryptophan-based polymer carbon dot corrosion inhibitor, characterized in that: The method comprises taking tryptophan and phenylalanine as reaction precursors, causing a condensation reaction between the molecules of the reaction precursors through a solvent thermal reaction, and obtaining the tryptophan-based polymer carbon dot corrosion inhibitor after post-treatment.

2. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 1, wherein Tryptophan is L-tryptophan; Phenylalanine is L-phenylalanine; and / or, the molar ratio of tryptophan to phenylalanine is (1-4):1 or 1:(1-4); And / or, the particle size of the tryptophan-based polymer carbon dot corrosion inhibitor is 5 to 10 nm.

3. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 1, wherein The solvothermal reaction comprises uniformly mixing the reaction precursor and the solvent and then reacting; And / or, the solvent is water and / or ethanol.

4. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 1, wherein The conditions of the solvent thermal reaction include: a reaction temperature of 150 to 250° C. and a reaction time of 5 to 15 hours.

5. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 1, wherein The post-treatment includes purification and drying of the condensation product.

6. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 5, wherein: The purification comprises cooling the condensation product to room temperature and then dialyzing it in a dialysis bag with a molecular weight cut-off of 1.0 to 3.0 kDa, the dialysis time being 12 to 24 hours.

7. The method for preparing the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 5, wherein: The drying method includes vacuum freeze drying; And / or, the drying time is 24 to 48 hours, and the drying temperature is -70 to -90°C.

8. A tryptophan-based polymer carbon dot corrosion inhibitor, prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the tryptophan-based polymer carbon dot corrosion inhibitor according to claim 8 in the corrosion protection of metal materials in an acidic environment.

10. The use according to claim 9, wherein the metal material comprises any one of carbon steel, copper, aluminum and other alloys; The acidic conditions include: Any of hydrochloric acid, sulfuric acid, nitric acid, carbonic acid, and phosphoric acid solutions with a pH of ~ 0; The concentration of the tryptophan-based polymer carbon dot corrosion inhibitor is 50 to 200 mg·L- 1 .

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