A corrosion-inhibiting metal pickling solution, its preparation method and its application

Abstract

The present invention relates to the field of pickling, and specifically relates to a corrosion-inhibiting metal pickling solution, a preparation method thereof, and an application thereof. By separately synthesizing two reagents, namely a carbon dot corrosion inhibitor with a nanostructure and a compounding agent compounded with a surfactant and a corrosion inhibitor, an acid pickling solution with good corrosion inhibition effect and environmental protection can be synthesized, and the addition of the compounding agent can improve the cleaning effect of pickling. Compared with the acid pickling solutions in the prior art, the corrosion inhibition effect on the metal surface can be improved, and natural chitosan compounds are used for synthesizing the reagents, so that the final acid pickling solution has better environmental protection performance, and while ensuring the corrosion inhibition effect, the environmental pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the field of pickling, and particularly relates to a corrosion - inhibiting metal pickling solution, a preparation method thereof, and an application thereof. Background Art

[0002] At present, there are many problems with the pickling solutions commonly used in the pretreatment process before electroplating, such as the inability to effectively control the corrosion of acids to metal materials, poor corrosion - inhibition effect, poor environmental protection performance, etc. Especially when treating materials with high carbon content and heat - treated materials, black carbon ash is likely to be generated on the surface oxide film during pickling treatment, which affects the electroplating adhesion and plating speed. At the same time, too thick oxide scale will lead to a long pickling time, and then cause over - corrosion of the material. In addition, high - strength materials are also prone to increasing the possibility of hydrogen embrittlement during pickling.

[0003] In the pretreatment process before electroplating, the use of corrosion inhibitors is crucial for protecting metal materials from acid corrosion. However, the commonly used corrosion inhibitors at present have many defects, including poor corrosion - inhibition effect, improper proportion control that is likely to cause metal corrosion, poor effect under strong acid conditions, and poor environmental protection performance. These problems are particularly prominent when treating materials with high carbon content and heat - treated materials. Summary of the Invention

[0004] In order to solve the above problems, the embodiments of the present application provide a corrosion - inhibiting metal pickling solution, a preparation method thereof, and an application thereof. By adding a corrosion inhibitor and a surface - active agent with corrosion - inhibition compounding in an acid solution, the corrosion - resistance ability of metals in an acid environment can be significantly improved, and environmental pollution can be reduced.

[0005] In order to achieve the above object, the technical solutions adopted in the embodiments of the present application are as follows:

[0006] In the first aspect, a corrosion - inhibiting metal pickling solution is provided, which includes an acid solution, a corrosion inhibitor, and a surface - active agent. The corrosion inhibitor is a sulfur - doped carbon dot polymer corrosion inhibitor, the content of the corrosion inhibitor is 1 - 30 g / L, the surface - active agent is a compounding agent obtained by equimolar compounding of 2 - aminobenzimidazole and a cationic biosurfactant, the content of the surface - active agent is 10 - 40 g / L, the acid solution is a hydrochloric acid solution, and the content of the acid solution is 40 - 500 ml / L.

[0007] In some specific implementation manners, the corrosion inhibitor is a sulfur - doped chitosan derivative carbon dot corrosion inhibitor synthesized by a hydrothermal method based on chitosan Schiff base, 8 - hydroxyquinoline, and thiourea.

[0008] In some specific implementation manners, the cationic biosurfactant is an alkyl glycoside derivative surfactant synthesized from alkyl glycoside ester and tertiary amine polyether.

[0009] Second aspect, a method for preparing a corrosion - inhibiting metal pickling solution is provided, which is used to prepare the corrosion - inhibiting metal pickling solution described in any one of the above, and includes the following steps: Step 1: Using chitosan Schiff base, 8 - hydroxyquinoline and thiourea as raw materials, a sulfur - doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method; Step 2: An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is compounded with 2 - aminobenzimidazole in an equimolar ratio to obtain a compounding agent; Step 3: A hydrochloric acid solution with a concentration of 10% - 40% is prepared as the acid solution, and the sulfur - doped chitosan derivative carbon dot corrosion inhibitor and the compounding agent are added to the acid solution and mixed evenly to obtain the corrosion - inhibiting metal pickling solution.

[0010] In some specific implementation manners, Step 1 further includes: Dissolving equal weights of the chitosan Schiff base, 8 - hydroxyquinoline and thiourea in an equimolar amount of hydrochloric acid solution to obtain a mixed solution, heating and drying the mixed solution to obtain an intermediate product, and successively filtering, dialyzing and drying the intermediate product to obtain the sulfur - doped chitosan derivative carbon dot corrosion inhibitor.

[0011] In some specific implementation manners, Step 2 further includes: Stirring and mixing methoxy polyethylene glycol monomethyl ether with terminal epoxy groups and N,N - dimethylethylenediamine, and obtaining tertiary amine polyether by vacuum distillation of the mixed solution.

[0012] In some specific implementation manners, the molar ratio of the epoxy group to the secondary amine in the methoxy polyethylene glycol monomethyl ether with terminal epoxy groups and N,N - dimethylethylenediamine is 2.0:1.3, the stirring and mixing temperature is 80 °C, and the stirring time is four hours.

[0013] In some specific implementation manners, Step 2 further includes: Dissolving the alkyl glycoside ester and the tertiary amine polyether in an N,N - dimethylformamide solution in a mass ratio of 1:1.2, stirring under catalyst conditions and performing condensation reflux at 105 °C to obtain an intermediate product, and successively filtering, vacuum distilling and solvent washing the intermediate product, and drying to obtain the alkyl glycoside derivative surfactant.

[0014] In some specific implementation manners, the catalyst is potassium iodide, and the catalyst content is 0.5% of the total reaction substances.

[0015] Third aspect, an application of the above - mentioned corrosion - inhibiting metal pickling solution in the cleaning of iron products before electroplating is provided.

[0016] In the technical solution provided by the embodiments of the present application, by separately synthesizing two reagents, namely a carbon dot corrosion inhibitor with a nanostructure and a compounding agent compounded with a surfactant and a corrosion inhibitor, an acid cleaning solution with good corrosion inhibition effect and environmental protection can be synthesized, and the addition of the compounding agent can improve the cleaning effect of acid cleaning. Compared with the acid cleaning solutions in the prior art, it can improve the corrosion inhibition effect on the metal surface, and natural chitosan compounds are used for the synthesis of the reagents. The final acid cleaning solution is more environmentally friendly, reducing environmental pollution while ensuring the corrosion inhibition effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0018] Figure 1 It is a flowchart of the method for preparing a corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0019] Figure 2 It is a schematic diagram of the corrosion efficiency results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0020] Figure 3 It is a schematic diagram of the corrosion inhibition efficiency results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0021] Figure 4 It is a Nyquist diagram of the electrochemical impedance spectroscopy test results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0022] Figure 5 It is a Bode diagram of the electrochemical impedance spectroscopy test results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0023] Figure 6 It is a schematic diagram of the potentiodynamic polarization test results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0024] Figure 7 It is a schematic diagram of the reaction gas detection results of the corrosion-inhibiting metal acid cleaning solution provided by the embodiments of the present application.

[0025] Figure 8 It is a schematic diagram of the results of a comparative experiment provided by the embodiments of the present application.

[0026] Figure 9 It is a schematic diagram of the results of another comparative experiment provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase. The embodiments described below are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art in combination with the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0028] In a specific embodiment of the present invention, the present invention provides a corrosion-inhibiting metal pickling solution, which is composed of at least three components and includes at least an acid solution, a corrosion inhibitor, and a surfactant.

[0029] Among them, the acid solution is the main component of the pickling solution and is used to remove oxides and rust on the metal surface. Specifically, in this embodiment, the acid solution is a hydrochloric acid solution, and the content of the acid solution is 40 - 500 ml / L. The corrosion inhibitor is used to reduce the corrosion of the pickling solution on the metal matrix. Specifically, in this embodiment, the corrosion inhibitor is a sulfur-doped carbon dot polymer corrosion inhibitor, and the content of the corrosion inhibitor is 1 - 30 g / L. The surfactant can reduce the surface tension of the liquid, making the pickling solution easier to penetrate and wet the surface of the object to be cleaned, thereby improving the cleaning effect. Specifically, in this embodiment, the surfactant is a complexing agent obtained by equimolar complexing of 2-aminobenzimidazole and a cationic biosurfactant, and the content of the surfactant is 10 - 40 g / L.

[0030] In this embodiment, the corrosion inhibitor is not a single compound in the prior art but a biomass carbon dot based on synthesis. Specifically, the corrosion inhibitor is a sulfur-doped chitosan derivative carbon dot corrosion inhibitor synthesized by chitosan Schiff base, 8-hydroxyquinoline, and thiourea through a hydrothermal method. Among them, the chitosan Schiff base has a Schiff base structure, and the chitosan Schiff base is modified with 8-hydroxyquinoline hydrochloride to obtain a chitosan derivative, and the chitosan derivative is carbon-dotted to form a sulfur-doped carbon-based nano-polymer, which can be used as a green corrosion inhibitor. The carbon dot corrosion inhibitor has the characteristics of easy access to raw materials, wide sources, and simple preparation process, and also has low in vitro and in vivo toxicity, biocompatibility, and biodegradability. Therefore, this type of corrosion inhibitor is beneficial to reducing environmental pollution and human health risks.

[0031] In this embodiment, the surfactant used is not a compound in the prior art either. It is also obtained through synthesis and compounding. The logic behind this setting is that the surfactant in this embodiment is not only used to reduce the surface tension of the liquid, reduce the generation of foam, and thus reduce acid mist, but also to improve the corrosion inhibition effect. By compounding corrosion inhibition components, it can combine with corrosion inhibitors to achieve the corrosion inhibition effect during the pickling process.

[0032] Specifically, the biosurfactant in this embodiment is a compound obtained by equimolar compounding of 2-aminobenzimidazole and a cationic biosurfactant. Among them, the cationic biosurfactant is an alkyl glycoside derivative surfactant synthesized based on alkyl glycoside esters and tertiary amine polyethers. For the overall acid solution, the surfactant is not only used to improve the cleaning effect, but also serves as a solution system for corrosion inhibitors and can be combined with the above-mentioned carbon dots to form a systematic corrosion inhibitor.

[0033] The corrosion inhibition principle of the surfactant is that when the surfactant is used in a solution, it can form a protective film on the metal surface to be cleaned, thereby further improving the corrosion inhibition effect.

[0034] However, it should be noted that the corrosion inhibition efficiency of the surfactant alone decreases significantly with the increase in temperature. The pickling process is an obvious exothermic process, and the temperature during the reaction will increase and then decrease with time. Therefore, in order to improve the corrosion inhibition effect of the surfactant on the basis of ensuring the unchanged cleaning effect of the surfactant, this is achieved by compounding corrosion inhibitors in this embodiment. One of the compound corrosion inhibitors selected in this embodiment is 2-aminobenzimidazole. After adding 2-aminobenzimidazole and compounding it with the surfactant, the corrosion effect of the solution at high temperature can be inhibited, thus making up for the shortcoming of the poor heat resistance of the surfactant and improving the working efficiency of the surfactant.

[0035] Moreover, in this embodiment, a cationic surfactant is used for the surfactant. For the cationic surfactant, it has better electron-donating ability compared to ordinary surfactants. The improvement of the electron-donating ability makes it easier to combine with metals to form an adsorption film, thereby improving the corrosion inhibition effect of the surfactant. Therefore, in this embodiment, by compounding the cationic surfactant with 2-aminobenzimidazole, the corrosion inhibition ability of the surfactant during the overall reaction process is improved.

[0036] Further, the cationic surfactant in this embodiment is an alkyl polyglycoside surfactant. Among them, alkyl polyglycoside is a green surfactant. On the basis of retaining the advantages of alkyl polyglycoside, a cation and a polyoxyethylene chain are introduced into the structure, effectively improving the solvent affinity of alkyl polyglycoside, making it easy to penetrate and wet the surface of the object to be cleaned, and further improving the cleaning effect of the pickling solution.

[0037] Therefore, in this embodiment, by introducing a cationic alkyl polyglycoside derivative surfactant and 2-aminobenzimidazole for compounding, the corrosion inhibition effect and cleaning effect of the pickling solution are improved as a whole. And because of the green performance of the alkyl polyglycoside derivative, the pollution of the pickling solution to the environment is reduced, and it has higher environmental protection performance.

[0038] Based on the above corrosion inhibition metal pickling solution, in this embodiment, a preparation method is also provided, which is obtained by mixing the above corrosion inhibitor, the corresponding compounding agent of the surfactant, and the acid solution. Also, since the above carbon dot corrosion inhibitor and the corresponding compounding agent of the surfactant are not directly available for purchase. Therefore, in this embodiment, the above reagents need to be synthesized before the solution mixing. For the specific preparation method in this embodiment, refer to Figure 1 , including the following specific steps:

[0039] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method.

[0040] Among them, in this step, chitosan Schiff base, 8-hydroxyquinoline, and thiourea of equal weight are dissolved in an equimolar amount of hydrochloric acid solution to obtain a mixed solution. After heating and drying the mixed solution, an intermediate product is obtained. The intermediate product is successively filtered, dialyzed, and dried to obtain a sulfur-doped chitosan derivative carbon dot corrosion inhibitor.

[0041] Specifically, take the same mass of chitosan Schiff base, 8-hydroxyquinoline, and thiourea and dissolve them in an equimolar amount of hydrochloric acid solution, then fully dissolve them to obtain a mixed solution. Transfer this mixed solution to a high-temperature and high-pressure autoclave and heat it by hot air drying at 200 °C for 24 h. After heating, cool it to room temperature to obtain a mixture, and filter this mixture through a 0.22 μm filter membrane to obtain a crude product.

[0042] It should be noted that at room temperature, the mixture is still a solution. Dialyze the mixture in deionized water to remove unreacted small molecule impurities. Finally, remove the solvent by rotary evaporation, collect the final product, and freeze-dry it under vacuum to completely dehydrate to obtain the final solid product, which is a sulfur-doped chitosan derivative carbon dot corrosion inhibitor.

[0043] Step S2. Synthesize an alkyl polyglycoside derivative surfactant from an alkyl polyglycoside ester and a tertiary amine polyether, and perform equimolar compounding of the alkyl polyglycoside derivative surfactant with 2-aminobenzimidazole to obtain a compounding agent.

[0044] Among them, the tertiary amine polyether in this embodiment is obtained by synthesis. Specifically, terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine are stirred and mixed at a temperature of 80 °C for four hours, and the mixed solution is obtained by vacuum distillation to obtain a tertiary amine polyether. Among them, the molar ratio of the epoxy group and secondary amine in terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine is: 2.0:1.3.

[0045] Then, the alkyl polyglycoside ester and the tertiary amine polyether are dissolved in an N,N-dimethylformamide solution in a mass ratio of 1:1.2, and stirred under the condition of potassium iodide as a catalyst and refluxed under condensation at 105 °C to obtain an intermediate product. The intermediate product is successively filtered, vacuum distilled and solvent washed, and dried to obtain an alkyl polyglycoside derivative surfactant. Then, the obtained alkyl polyglycoside derivative surfactant is subjected to equimolar compounding with 2-aminobenzimidazole to obtain a final compounding agent.

[0046] Among them, in this embodiment, the content of potassium iodide accounts for 0.5% of the total reaction substances.

[0047] Step S3. Prepare a hydrochloric acid solution with a concentration of 10% - 40% as an acid solution, and add the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the compounding agent to the acid solution, and mix evenly to obtain a corrosion-inhibiting metal pickling solution.

[0048] In this embodiment, the content of the sulfur-doped chitosan derivative carbon dot corrosion inhibitor is 1 - 30 g / L, the content of the compounding agent is 10 - 40 g / L, and the content of the acid solution is 40 - 500 ml / L. The above reagents are mixed and stirred evenly to obtain a final corrosion-inhibiting metal pickling solution.

[0049] The following further illustrates the corrosion-inhibiting metal pickling solution and the corresponding preparation method according to the present invention through specific examples.

[0050] Example 1

[0051] This example provides a corrosion-inhibiting metal pickling solution, which includes the following components:

[0052] 1 g / L of corrosion inhibitor, 10 g / L of compounding agent, and 500 ml / L of 40% hydrochloric acid solution. Among them, the corrosion inhibitor is a sulfur-doped carbon nanodot polymer corrosion inhibitor, and the compounding agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant in equimolar compounding.

[0053] The preparation method of the corrosion inhibitor-containing metal pickling solution in this embodiment includes the following steps:

[0054] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method.

[0055] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is complexed with 2-aminobenzimidazole in equimolar amounts to obtain a complexing agent.

[0056] Step S3. A hydrochloric acid solution with a concentration of 40% is prepared as the acid solution, and the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the complexing agent are added to the acid solution and mixed evenly to obtain the corrosion inhibitor-containing metal pickling solution.

[0057] Example 2

[0058] A corrosion inhibitor-containing metal pickling solution provided in this embodiment includes the following components:

[0059] Corrosion inhibitor 10 g / L, complexing agent 20 g / L, 400 ml / L of 40% hydrochloric acid solution. Among them, the corrosion inhibitor is a sulfur-doped carbon nanodot polymer corrosion inhibitor, and the complexing agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant complexed in equimolar amounts.

[0060] The preparation method of the corrosion inhibitor-containing metal pickling solution in this embodiment includes the following steps:

[0061] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method.

[0062] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is complexed with 2-aminobenzimidazole in equimolar amounts to obtain a complexing agent.

[0063] Step S3. A hydrochloric acid solution with a concentration of 40% is prepared as the acid solution, and the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the complexing agent are added to the acid solution and mixed evenly to obtain the corrosion inhibitor-containing metal pickling solution.

[0064] Example 3

[0065] A corrosion inhibitor-containing metal pickling solution provided in this embodiment includes the following components:

[0066] Inhibitor: 15 g / L, compounding agent: 25 g / L, 30% hydrochloric acid solution: 400 ml / L. Among them, the inhibitor is a sulfur-doped carbon nanodot polymer inhibitor, and the compounding agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant in equimolar compounding.

[0067] For the preparation method of the corrosion-inhibiting metal pickling solution in this example, it includes the following steps:

[0068] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot inhibitor is synthesized by a hydrothermal method.

[0069] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is compounded with 2-aminobenzimidazole in equimolar amounts to obtain a compounding agent.

[0070] Step S3. Prepare a 30% hydrochloric acid solution as the acid solution, and add the sulfur-doped chitosan derivative carbon dot inhibitor and the compounding agent to the acid solution, and mix evenly to obtain the corrosion-inhibiting metal pickling solution.

[0071] Example 4

[0072] A corrosion-inhibiting metal pickling solution provided in this example includes the following components:

[0073] Inhibitor: 20 g / L, compounding agent: 30 g / L, 30% hydrochloric acid solution: 300 ml / L. Among them, the inhibitor is a sulfur-doped carbon nanodot polymer inhibitor, and the compounding agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant in equimolar compounding.

[0074] For the preparation method of the corrosion-inhibiting metal pickling solution in this example, it includes the following steps:

[0075] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot inhibitor is synthesized by a hydrothermal method.

[0076] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is compounded with 2-aminobenzimidazole in equimolar amounts to obtain a compounding agent.

[0077] Step S3. Prepare a 30% hydrochloric acid solution as the acid solution, and add the sulfur-doped chitosan derivative carbon dot inhibitor and the compounding agent to the acid solution, and mix evenly to obtain the corrosion-inhibiting metal pickling solution.

[0078] Example 5

[0079] In this embodiment, a corrosion-inhibiting metal pickling solution is provided, which includes the following components:

[0080] Corrosion inhibitor: 25 g / L, compounding agent: 35 g / L, 40% hydrochloric acid solution: 300 ml / L. Among them, the corrosion inhibitor is a sulfur-doped carbon nanodot polymer corrosion inhibitor, and the compounding agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant in equimolar compounding.

[0081] The preparation method of the corrosion-inhibiting metal pickling solution in this embodiment includes the following steps:

[0082] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method.

[0083] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is compounded with 2-aminobenzimidazole in equimolar amounts to obtain a compounding agent.

[0084] Step S3. Prepare a hydrochloric acid solution with a concentration of 30% as the acid solution, and add the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the compounding agent to the acid solution, and mix evenly to obtain the corrosion-inhibiting metal pickling solution.

[0085] Example 6

[0086] In this embodiment, a corrosion-inhibiting metal pickling solution is provided, which includes the following components:

[0087] Corrosion inhibitor: 30 g / L, compounding agent: 40 g / L, 40% hydrochloric acid solution: 200 ml / L. Among them, the corrosion inhibitor is a sulfur-doped carbon nanodot polymer corrosion inhibitor, and the compounding agent is a mixture of 2-aminobenzimidazole and a cationic biosurfactant in equimolar compounding.

[0088] The preparation method of the corrosion-inhibiting metal pickling solution in this embodiment includes the following steps:

[0089] Step S1. Using chitosan Schiff base, 8-hydroxyquinoline, and thiourea as raw materials, a sulfur-doped chitosan derivative carbon dot corrosion inhibitor is synthesized by a hydrothermal method.

[0090] Step S2. An alkyl glycoside derivative surfactant is synthesized from alkyl glycoside ester and tertiary amine polyether, and the alkyl glycoside derivative surfactant is compounded with 2-aminobenzimidazole in equimolar amounts to obtain a compounding agent.

[0091] Step S3. Prepare a hydrochloric acid solution with a concentration of 40% as the acid solution, and add the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the compounding agent to the acid solution, and mix evenly to obtain the corrosion-inhibiting metal pickling solution.

[0092] Experimental Example 1

[0093] In this example, the corrosion rate and corrosion inhibition efficiency of the corrosion inhibitor-containing metal pickling solution corresponding to Examples 1-6 were tested by the weight loss method. Specifically, the corrosion rate and corrosion inhibition efficiency of the pickling solutions with different components in Examples 1-6 on N80 carbon steel were measured by the weight loss method at 30 °C. The results can be referred to Figure 2 and Figure 3 , where Figure 2 is used to illustrate the corrosion rate of the corrosion inhibitor-containing metal pickling solution corresponding to Examples 1-6, Figure 3 is used to illustrate the corrosion inhibition efficiency of the corrosion inhibitor-containing metal pickling solution corresponding to Examples 1-6.

[0094] From Figure 2 it can be seen that as the concentrations of the corrosion inhibitor and the compounding agent increase, the corrosion efficiency gradually decreases, while the corrosion inhibition efficiency gradually increases. Moreover, for the components of the corrosion inhibitor and the compounding agent used in Example 2, its corrosion inhibition efficiency has exceeded 90%, which indicates that the pickling solution corresponding to the component ratio in Example 2 already has an efficient corrosion inhibition effect, indicating that the use of sulfur-doped carbon nanodot aggregates corrosion inhibitor and surfactant can effectively inhibit the corrosion of carbon steel in hydrochloric acid.

[0095] Experimental Example 2

[0096] In this example, electrochemical impedance spectroscopy (EIS) tests and potentiodynamic polarization tests were carried out on Examples 1-6 by electrochemical testing methods. Among them, the electrochemical measurements were carried out on an electrochemical workstation, which was equipped with a three-electrode system including a working electrode, a reference electrode, and an auxiliary electrode. Before each electrochemical test, the carbon steel sample was polished step by step with SiC sandpaper, and then rinsed with deionized water and isopropanol respectively.

[0097] Among them, first, the open-circuit potential was tested for 0.5 h to ensure that the system was in a steady state, and then the electrochemical impedance spectroscopy test was carried out with a sinusoidal alternating current amplitude of 5 mV and a frequency range of 100 kHz to 10 mHz.

[0098] Regarding the electrochemical impedance results, refer to Figure 4 and Figure 5 , Figure 4 is the Nyquist diagram of the electrochemical impedance, Figure 5 is the Bode diagram of the electrochemical impedance. From Figure 4 and Figure 5It can be seen that in the pickling solution without the components of Examples 1 - 6 above, i.e., the blank group (Blank group), and in the Nyquist and Bode plots corresponding to the pickling solutions with the components of Examples 1 - 6 added, the shapes of the curves are similar, indicating that adding corrosion inhibitors and compounding agents to the acid solution does not change the corrosion mechanism of the acid solution. However, for Figure 4 As shown in the corresponding Nyquist plot, when the corrosion inhibitors and compounding agents with different components above are not added, due to the contact between the carbon steel surface and the solution, serious corrosion will occur, so the diameter of the capacitive reactance arc and the impedance modulus of the carbon steel are small. After adding different proportions of corrosion inhibitors and compounding agents in Examples 1 - 6, both values increase correspondingly, and as the concentration of the corrosion inhibitor and compounding agent increases, the radius of the capacitive reactance arc shows an upward trend. This is because the carbon steel surface is covered by more particles with corrosion inhibition effects. That is to say, the compactness of the protective film formed on the carbon steel surface increases with the increase in the concentration of the corrosion inhibitor and compounding agent. And, according to Figure 5 it can be seen that as the concentration of the corrosion inhibitor and compounding agent increases, the corrosion rate shows a gradually decreasing trend.

[0099] Experimental Example 3

[0100] To further illustrate the technical effects of the pickling solutions corresponding to Examples 1 - 6, in this example, an equivalent circuit simulation is established to test the corrosion inhibition effect. The impedance spectra are respectively fitted under different conditions through the equivalent circuit and the existing simulation calculation software ZSimWin, and the relevant fitting parameters are summarized in Table 1. Among them, Rs ( / Ω·cm -2 ), is the solution resistance, Rp ( / Ω·cm -2 ), is the polarization resistance, CPE1Y0×10 -4 / (S·s n ·cm -2 ), is the double - layer CPE element, and CPE2Y0×10 -4 / (S·s n ·cm -2 ), represents the film - covered capacitance.

[0101] Rs CPE1 CPE2 Rp Blank group 1.19 15.24 - 4.87 Example 1 2.071 1.812 54.725 41.54 Example 2 2.253 1.666 34.381 62.56 Example 3 1.866 1.456 25.425 114.28 Example 4 2.059 1.362 13.168 118.43 Example 5 2.117 1.179 11.521 127.03 Example 6 2.148 0.9532 5.438 199.81

[0102] Table 1. Fitting parameter table

[0103] As can be seen from Table 1, the change in the resistance Rs of the solution for different embodiments under different conditions is not obvious, which means that the addition of corrosion inhibitors and compounding agents in Embodiments 1-6 does not affect the properties of the acid solution. Moreover, as the concentrations of the corrosion inhibitors and compounding agents in Embodiments 1-6 increase, the polarization resistance Rp continuously increases, indicating that the pickling solution after adding the above reagents can continuously replace the water molecules on the surface of carbon steel during the reaction, thus forming a protective film, and the protective film becomes denser with the increase in concentration.

[0104] Experimental Example 4

[0105] To further illustrate the technical effects of the pickling solutions corresponding to Embodiments 1-6, in this embodiment, the environmental protection of the reaction gas is detected by setting up gas detection. Specifically, the reaction scenarios of the blank group and Embodiments 1-6 are set up, and the acid mist gas concentration of the reaction gas is detected by an acid mist detector, and the gas sensitivity detection of the acid mist detector is used as the evaluation data. The evaluation data is RLS, where the RLS intensity refers to the intensity of Rayleigh Light Scattering (RLS). RLS is a physical phenomenon. When light passes through a medium, the particles in the medium will scatter the light to form RLS. The RLS intensity will change with the change of external conditions. For example, the change in the pH value of the solution will cause the change in the RLS intensity. Specifically, when the pH value of the solution gradually increases, the RLS intensity will gradually decrease.

[0106] For the specific results, please refer to Figure 7 As shown, as the concentrations of the corrosion inhibitors and compounding agents added in the pickling solution increase, the gradual decrease in the RLS intensity indicates that the pickling solutions in Embodiments 1-6 can reduce the generation of acid mist during the pickling process, thus reducing environmental pollution and being an environmentally friendly pickling solution.

[0107] Comparative Example 1

[0108] In this embodiment, the surface reaction conditions of the pickling solution in Embodiment 6 and the pickling solution added with a corrosion inhibitor of the prior art are compared by the observation method.

[0109] Specifically, please refer to Figure 8 , in Figure 8 the left side shows the surface reaction state of the pickling solution added with the Norodin-type corrosion inhibitor in the prior art, Figure 8 and the right side in Figure 8 shows the surface reaction state of the pickling solution in Embodiment 6. As can be seen from

[0110] Please refer toFigure 9 , on the left side in Figure 9 is another reaction state of the pickling solution with the addition of the existing technology of Nordin corrosion inhibitor, Figure 9 and on the right side is the surface reaction state of the pickling solution in Example 6. It can be seen from Figure 9 that for the reaction on the left side, dense bubbles can be seen on the surface of the screw, indicating that the reaction is relatively strong at this time, while there are basically no bubbles on the surface of the screw on the right side.

[0111] Regarding the corrosion-inhibiting metal pickling solution and the corresponding preparation method provided in Examples 1-6 of the present invention, by separately synthesizing two reagents, namely a carbon dot corrosion inhibitor with a nanostructure and a compounding agent compounded with a surfactant and a corrosion inhibitor, a pickling solution with good corrosion inhibition effect and environmental protection can be synthesized, and the addition of the compounding agent can improve the cleaning effect of pickling. Compared with the pickling solution in the prior art, it can improve the corrosion inhibition effect on the metal surface, and natural chitosan compounds are used for the synthesis of the reagent, and the final pickling solution is more environmentally friendly, reducing environmental pollution while ensuring the corrosion inhibition effect.

[0112] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A corrosion-inhibiting metal pickling solution, comprising an acid solution, a corrosion inhibitor and a surfactant, characterized in that, The corrosion inhibitor is a sulfur-doped carbon dot polymer corrosion inhibitor, and the content of the corrosion inhibitor is 1-30 g / L. The surfactant is a compounding agent obtained by equimolar compounding of 2-aminobenzimidazole and a cationic biosurfactant, and the content of the surfactant is 10-40 g / L. The acid solution is a hydrochloric acid solution, and the content of the acid solution is 40-500 ml / L; the corrosion inhibitor is synthesized by a hydrothermal method based on chitosan Schiff base, 8-hydroxyquinoline and thiourea, specifically including: taking the same mass of chitosan Schiff base, 8-hydroxyquinoline and thiourea and dissolving them in an equimolar amount of hydrochloric acid solution for full dissolution to obtain a mixed solution, heating and drying the mixed solution in a high-temperature and high-pressure autoclave at 200 °C for 24 h and then cooling to room temperature to obtain a mixture, filtering the mixture to obtain a crude product, dialyzing in deionized water and then performing rotary evaporation, and freeze-drying under vacuum to completely dehydrate; the cationic biosurfactant is an alkyl glycoside derivative surfactant synthesized from alkyl glycoside ester and tertiary amine polyether, specifically including: stirring and mixing terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine at 80 °C, and obtaining tertiary amine polyether by subjecting the mixed solution to vacuum distillation; the molar ratio of the epoxy group to the secondary amine in terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine is: 2.0:1.3; then dissolving alkyl glycoside ester and tertiary amine polyether in N,N-dimethylformamide solution in a mass ratio of 1:1.2, stirring under the condition of using potassium iodide as a catalyst and performing condensation reflux at 105 °C to obtain an intermediate product, and successively filtering, vacuum distilling and solvent washing the intermediate product, and drying to obtain it.

2. A method for preparing a corrosion-inhibiting metal pickling solution, which is used to prepare the corrosion-inhibiting metal pickling solution described in claim 1, characterized in that, It includes the following steps: Step 1: Using chitosan Schiff base, 8-hydroxyquinoline and thiourea as raw materials, synthesizing a sulfur-doped chitosan derivative carbon dot corrosion inhibitor by a hydrothermal method; Step 2: Synthesizing an alkyl glycoside derivative surfactant from alkyl glycoside ester and tertiary amine polyether, and performing equimolar compounding of the alkyl glycoside derivative surfactant and 2-aminobenzimidazole to obtain a compounding agent; Step 3: Preparing a hydrochloric acid solution with a concentration of 10%-40% as the acid solution, and adding the sulfur-doped chitosan derivative carbon dot corrosion inhibitor and the compounding agent to the acid solution, and mixing evenly to obtain a corrosion-inhibiting metal pickling solution.

3. The method for preparing a corrosion-inhibiting metal pickling solution according to claim 2, characterized in that, Step 1 further includes: dissolving the chitosan Schiff base, 8-hydroxyquinoline and thiourea in equal weights in an equimolar amount of hydrochloric acid solution to obtain a mixed solution, heating and drying the mixed solution to obtain an intermediate product, and successively filtering, dialyzing and drying the intermediate product to obtain the sulfur-doped chitosan derivative carbon dot corrosion inhibitor.

4. The method for preparing the corrosion-inhibiting metal pickling solution according to claim 2, characterized in that, Step 2 further includes: stirring and mixing terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine, and obtaining tertiary amine polyether by subjecting the mixed solution to vacuum distillation.

5. The preparation method of the corrosion-inhibiting metal pickling solution according to claim 4, wherein The molar ratio of the epoxy group to the secondary amine in the terminal epoxy polyethylene glycol monomethyl ether and N,N-dimethylethylenediamine is: 2.0:1.3, the stirring and mixing temperature is 80 °C, and the stirring time is four hours.

6. The method for preparing a corrosion-inhibiting metal pickling solution according to claim 2, wherein, The second step further includes: dissolving the alkyl glycoside ester and the tertiary amine polyether in an N,N-dimethylformamide solution in a mass ratio of 1:1.2, stirring under catalyst conditions, and performing condensation reflux at 105 °C to obtain an intermediate product. The intermediate product is successively filtered, subjected to vacuum distillation, and solvent washed, and after drying, the alkyl glycoside derivative surfactant is obtained.

7. The preparation method of the corrosion inhibitor-containing metal pickling solution according to claim 6, wherein, The catalyst is potassium iodide, and the catalyst content is 0.5% of the total reaction substances.

8. Use of the corrosion-inhibiting metal pickling solution according to claim 1, characterized in that, Application of the corrosion inhibitor metal pickling solution in the cleaning of iron products before electroplating.

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