In-situ preparation method of steel bar corrosion-resistant coating based on electrochemical re-alkalization

Abstract

The invention discloses an electrochemical re-alkalization-based in-situ preparation method of a steel bar corrosion-resistant coating, and belongs to the technical field of reinforced concrete repair, the electrochemical re-alkalization-based in-situ preparation method of the steel bar corrosion-resistant coating comprises the following steps: S1, preparing an oxygen-enriched aqueous solution; s2, preparing a mixed solution rich in divalent metal salt and trivalent metal salt; s3, the titanium mesh and the steel bars in the reinforced concrete are connected to the positive electrode and the negative electrode of a direct-current power source respectively, and an alkaline environment is formed on the surfaces of the steel bars which are confirmed to be rusted through electrochemical re-alkalization; and S4, the oxygen-enriched aqueous solution is replaced with a mixed solution, and under the action of an electrostatic field, the metal hydroxide coating generated on the surface of the rusted reinforcing steel bar in situ is confirmed in the reinforced concrete. The metal hydroxide coating with high corrosion resistance can be generated on the rusted surface of the reinforcing steel bar in situ, so that the rusted part on the surface of the reinforcing steel bar is repaired, the corrosion resistance of reinforced concrete is improved, and in-situ prolonging of the service life of reinforced concrete structure engineering is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of reinforced concrete repair, in particular to an in-situ preparation method of a steel bar corrosion resistant coating based on electrochemical realkalinization. Background Art

[0002] Reinforced concrete is composed of steel bars and concrete. It is a widely used structural form in infrastructure construction. It combines the compressive strength of concrete and the tensile strength of steel bars, making the reinforced concrete structure have higher tensile and compressive properties.

[0003] In the existing technology, the raw materials of reinforced concrete are uneven, and the engineering service environment is complex. The corrosive media such as CO 3 2- 、SO 4 2- , Cl - The corrosion can penetrate the concrete protective layer through the microscopic pores in the concrete and cause electrochemical corrosion to the steel bars, causing rust and cracking. It is difficult to repair the reinforced concrete structures in service under harsh corrosive environments, which ultimately damages the integrity of the concrete structure and shortens the service life of the project. Summary of the invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes an in-situ preparation method of steel bar corrosion-resistant coating based on electrochemical realkalinization, which can repair rusted steel bars and improve the corrosion resistance of reinforced concrete.

[0005] The in-situ preparation method of the steel bar corrosion-resistant coating based on electrochemical realkalinization according to the embodiment of the present invention comprises: S1: preparing an oxygen-rich aqueous solution; S2: preparing a mixed solution rich in divalent metal salts and trivalent metal salts; S3: connecting the steel bars in the reinforced concrete to the negative electrode of a direct current power supply, connecting the titanium mesh in the oxygen-rich aqueous solution to the positive electrode of the direct current power supply, and performing realkalinization treatment by electrochemistry to form an alkaline environment on the surface of the steel bar confirmed to be corroded;

[0006] S4: The oxygen-rich aqueous solution is replaced with a mixed solution, and under the action of an electrostatic field, a metal hydroxide coating is generated in situ on the surface of the rusted steel bars in the reinforced concrete.

[0007] The in-situ preparation method of steel bar corrosion-resistant coating based on electrochemical realkalinization according to the embodiment of the present invention has at least the following beneficial effects: confirming that a high pH environment is formed on the surface of the rusted steel bar in concrete, and then using a mixed liquid to migrate divalent and trivalent metal cations to the rusted surface of the steel bar under the action of an electrostatic field, the divalent and trivalent metal cations react chemically with the hydroxide on the surface of the steel bar, and in-situ generate a metal hydroxide coating with strong corrosion resistance on the rusted surface of the steel bar, thereby repairing the rusted part of the steel bar surface, improving the corrosion resistance of reinforced concrete, extending the service life of the reinforced concrete structure, and realizing the in-situ improvement of the service life of the reinforced concrete structure project.

[0008] According to some embodiments of the present invention, in S1, preparing the oxygen-rich aqueous solution includes: continuously passing air into the ice-water mixture using a bubbler, and testing the oxygen content in the solution using a dissolved oxygen meter until the oxygen content in the solution reaches a preset oxygen content.

[0009] According to some embodiments of the present invention, the preset oxygen content of the oxygen-rich aqueous solution is greater than or equal to 10 mg / L.

[0010] According to some embodiments of the present invention, in S2, the concentration ratio of the divalent metal salt to the trivalent metal salt in the mixed solution is greater than or equal to 3:1.

[0011] According to some embodiments of the present invention, in S2, the divalent metal salt is selected from at least one of magnesium sulfate and zinc sulfate, and the trivalent metal salt is selected from at least one of aluminum nitrate and iron nitrate.

[0012] According to some embodiments of the present invention, in S3, the voltage range of the electrochemical realkalification is 15 to 30 V, and the duration of the electrochemical realkalification is 2 to 3 days.

[0013] According to some embodiments of the present invention, in S3, during the electrochemical realkalinization process, the chemical reaction formula on the surface of the steel bar is:

[0014] O 2 +2H 2 O+4e→4OH - ;

[0015] Among them, e is a negative electron.

[0016] According to some embodiments of the present invention, in S4, when the pH value in the concrete is greater than or equal to 12, the oxygen-rich aqueous solution is replaced with the mixed solution.

[0017] According to some embodiments of the present invention, in S4, the voltage used by the electrostatic field is in the range of 15 to 30 V, and the duration of the electrostatic field is 3 to 5 days.

[0018] According to some embodiments of the present invention, in S4, metal ions in the solution migrate to the surface of the steel bar confirmed to be corroded under the action of the electrostatic field and form the metal hydroxide coating, and the reaction process of the metal hydroxide coating is:

[0019]

[0020] Among them, M 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, x is a natural number, and y is a natural number.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0023] Figure 1 Schematic diagram of the electrochemical realkalinization process in the in-situ preparation method of the steel bar corrosion resistant coating based on electrochemical realkalinization in an embodiment of the present invention;

[0024] Figure 2 Schematic diagram of the process of in-situ generation of a coating in the in-situ preparation method of a steel bar corrosion-resistant coating based on electrochemical realkalinization according to an embodiment of the present invention;

[0025] Figure 3 is a comparison diagram of steel bar corrosion behavior at different stages in a specific embodiment of the present invention;

[0026] Figure 4 It is a comparison diagram of the pH value of concrete on the surface of steel bars at different stages in a specific embodiment of the present invention.

[0027] Reference numerals:

[0028] Oxygen-rich aqueous solution 100, mixed solution 200, power source 300, titanium mesh 400;

[0029] Reinforced concrete 10, steel 11, concrete 12, O 2 20, OH - 30,M 2+ 40,M 3+ 50. DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., and orientations or positional relationships indicated are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] In the description of the present invention, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0032] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0033] refer to Figures 1 to 4 The invention describes an in-situ preparation method of a steel bar corrosion resistant coating based on electrochemical realkalinization according to an embodiment of the invention.

[0034] like Figure 1 and Figure 2 As shown, according to the first aspect of the present invention, the in-situ preparation method of the steel bar corrosion resistant coating based on electrochemical realkalinization comprises:

[0035] S1: preparing an oxygen-rich aqueous solution 100;

[0036] S2: preparing a mixed solution 200 rich in divalent metal salt and trivalent metal salt;

[0037] S3: connecting the steel bars 11 in the reinforced concrete 10 to the negative electrode of the DC power supply 300, connecting the titanium mesh 400 in the oxygen-rich aqueous solution 100 to the positive electrode of the DC power supply 300, and performing a re-alkalization treatment through electrochemistry to form an alkaline environment on the surface of the steel bars 11 confirmed to be corroded;

[0038] S4: The oxygen-rich aqueous solution 100 is replaced with the mixed solution 200. Under the action of the electrostatic field, a metal hydroxide coating is formed in situ on the surface of the corroded steel bars 11 in the reinforced concrete 10.

[0039] Therefore, firstly, a high pH environment is formed on the surface of the corroded steel bar 11 in the concrete 12, and then the mixed liquid 200 is used to migrate divalent and trivalent metal cations to the corroded surface of the steel bar 11 under the action of the electrostatic field, and the divalent and trivalent metal cations chemically react with the hydroxide on the surface of the steel bar 11, and a metal hydroxide coating with strong corrosion resistance is generated in situ on the rusted surface of the steel bar 11, thereby repairing the rusted part of the surface of the steel bar 11, and improving the corrosion resistance of the reinforced concrete 10, thereby achieving an in-situ improvement in the service life of the reinforced concrete 10 structural engineering.

[0040] It should be noted that in the electrochemical re-alkalization treatment, voltage is mainly applied to the surface of the rusted steel bars 11 to form an alkaline environment to promote the migration and deposition of metal ions. However, the deposition of metal ions on the surface of the uncorroded steel bars 11 will be affected due to the lack of oxidation products or other corrosion-related substances, and the formation of the metal hydroxide coating requires specific electrochemical conditions and environment. These conditions are difficult to meet on the surface of the uncorroded steel bars 11, resulting in the inability to effectively form the coating. Therefore, the in-situ formation of the metal hydroxide coating mainly occurs on the surface of the rusted steel bars 11, and the coating will not be generated on the uncorroded steel bars 11.

[0041] In some specific embodiments of the present invention, in S1, preparing the oxygen-rich aqueous solution 100 includes: using a bubbler to continuously pass air into the ice-water mixture, and using a dissolved oxygen meter to test the oxygen content in the solution until the oxygen content in the solution reaches a preset oxygen content.

[0042] It should be noted that the oxygen dissolving capacity of water is higher at low temperatures. This characteristic can be used to increase the oxygen content in water, provide more oxygen for the reaction, and improve the reaction efficiency. Therefore, by using an ice-water mixture to prepare an oxygen-enriched aqueous solution 100, the solubility of oxygen in water can be increased, the redox reaction can be promoted, an alkaline environment can be formed in the electrochemical realkalinization treatment, and the reaction efficiency can be improved.

[0043] In some specific embodiments of the present invention, the preset oxygen content of the oxygen-rich aqueous solution 100 is greater than or equal to 10 mg / L.

[0044] In some specific embodiments of the present invention, in S2, the concentration ratio of the divalent metal salt to the trivalent metal salt in the mixed liquid 200 is greater than or equal to 3:1, so as to maintain an appropriate supply of metal ions, promote the electrochemical reaction, and facilitate the formation of a stable metal hydroxide coating, thereby improving the corrosion resistance and durability of the reinforced concrete 10 structure.

[0045] In some specific embodiments of the present invention, in S2, the divalent metal salt is selected from at least one of magnesium sulfate and zinc sulfate, and the trivalent metal salt is selected from at least one of aluminum nitrate and iron nitrate.

[0046] In some specific embodiments of the present invention, in S3, the voltage range of the electrochemical realkalification is 15 to 30 V, and the duration of the electrochemical realkalification is 2 to 3 days.

[0047] In some specific embodiments of the present invention, in S3, during the electrochemical realkalinization process, the chemical reaction formula on the surface of the steel bar 11 is:

[0048] O 2 +2H 2 O+4e→4OH - ;

[0049] Among them, e is a negative electron.

[0050] In some specific embodiments of the present invention, in S4 , when the pH value in the concrete 12 is greater than or equal to 12, the oxygen-enriched aqueous solution 100 is replaced with the mixed solution 200 .

[0051] It should be noted that the pH in the concrete 12 generally refers to the pH value of the capillary solution of the concrete 12 part of the reinforced concrete 10, rather than the pH value of the solution. As a key parameter, it reflects the chemical properties of the pore solution of the concrete 12, and is very important for evaluating the alkalinity and corrosion resistance of the concrete 12. Therefore, when the pH in the concrete 12 is greater than or equal to 12, it means that the pore solution of the concrete 12 has a very high alkalinity, that is, a high pH environment is formed on the surface of the steel bar 11, which helps to form a protective hydroxide coating to prevent further corrosion of the steel bar 11.

[0052] In some specific embodiments of the present invention, in S4, the voltage range of the electrostatic field is 15 to 30 V, and the duration of the electrostatic field is 3 to 5 days.

[0053] In some specific embodiments of the present invention, in S4, metal ions in the solution migrate to the surface of the steel bar 11 confirmed to be corroded under the action of the electrostatic field and form a metal hydroxide coating, and the reaction process of the metal hydroxide coating is:

[0054]

[0055] Among them, M 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, x is a natural number, and y is a natural number.

[0056] like Figure 1 and Figure 2 As shown, the in-situ preparation method of the steel bar corrosion-resistant coating based on electrochemical realkalinization is specifically described below with a specific implementation.

[0057] S1: A bubbler is used to continuously pass air into a 10 L ice-water mixture, and a dissolved oxygen meter is used to test the oxygen content in the solution. When the oxygen content in the solution is ≥10 mg / L, an oxygen-enriched aqueous solution 100 is obtained.

[0058] S2: Weigh 72g of magnesium sulfate and 42.6g of aluminum nitrate respectively, add them into another 10L of water, stir for 5min, and prepare Mg-containing 2+ and Al 3+ The concentrations are 0.06mol / L and 0.02mol / L respectively, with a mixed solution of 200 in a ratio of 3:1.

[0059] S3: Select marine reinforced concrete 10 test blocks that have been in service for more than 40 years, where the size of the concrete 12 test block is 10cm×10cm×10cm, and the size of the steel bar 11 is φ12mm. Use an electrochemical workstation to test the electrochemical polarization curve of the steel bar 11 in the concrete 12 to judge whether the steel bar 11 is corroded and record it as A, and test the initial pH value of the concrete 12 and record it as D.

[0060] The reinforced concrete 10 confirmed to be corroded is immersed in the oxygen-rich aqueous solution 100 for a period of time, and the oxygen-rich aqueous solution 100 penetrates the concrete 12 and infiltrates the surface of the steel bar 11. The steel bar 11 is connected to the negative electrode of the DC power supply 300, and the titanium mesh 400 is connected to the positive electrode of the DC power supply 300. The voltage is set to 20V, and the power-on time is set to 2 days. A high pH environment is created on the surface of the steel bar 11 through electrochemical re-alkalization. After the re-alkalization is completed, the electrochemical plan curve of the steel bar 11 is tested by an electrochemical workstation and recorded as B, and the pH value of the concrete 12 is tested and recorded as E.

[0061] When the pH value in the test concrete 12 is greater than or equal to 12, the oxygen-rich aqueous solution 100 is replaced with a mixed solution 200 containing a divalent metal salt and a trivalent metal salt, the DC voltage is set to 25 V, and the power-on time is set to 4 days. Under the action of the electrostatic field, the metal ions in the solution migrate to the surface of the steel bar 11 and chemically react with the hydroxide ions on the surface of the steel bar 11 to form a metal hydroxide coating, thereby achieving the goal of in-situ forming a corrosion-resistant coating on the surface of the steel bar 11.

[0062] The electrochemical polarization curve of the steel bar 11 is tested by an electrochemical workstation and recorded as C, and the pH value in the concrete 12 is tested and recorded as F.

[0063] Refer to Figure 3 The electrochemical test results shown in Figure 4 The pH test results of concrete 12 are shown in the figure. In the initial state, the corrosion potential of steel bar 11 in concrete 12 is -0.625V, and the corrosion current density is 4.9×10 -5 Acm-2 , the pH value is only 10. According to the judgment principle of steel bar 11 corrosion in concrete 12 in the Technical Specification for Inspection and Evaluation of Hydraulic Structures in Water Transport Engineering JTS 304-2019, steel bar 11 is already in a corroded state. After electrochemical re-alkalinization, the corrosion potential of steel bar 11 is -0.329V, and the corrosion current density is 2.6×10 -5 Acm -2 The corrosion potential significantly moved to the positive direction, the corrosion current density also decreased, and the pH value significantly increased to 12.5, indicating that the electrochemical realkalinization process improved the corrosion resistance of the steel bar 11. Furthermore, the metal hydroxide coating was prepared in situ on the surface of the steel bar 11 by electrochemical action. As shown in curve C, the corrosion potential and corrosion current density of the steel bar 11 were -0.208 V and 1.2×10 -5 Acm -2 , the pH value further increased to 13.1, and the steel bar 11 in the anode area showed a stable passivation range, and the depassivation potential was +0.466V. It should be further explained that rust spots appeared on the surface of the steel bar 11 before treatment, and the rust sites on the surface of the steel bar 11 after treatment were significantly reduced, and a layer of white metal hydroxide coating was formed in situ on the surface of the rust spots. The above results show that through electrochemical step-by-step operation, a corrosion-resistant coating can be formed in situ on the surface of the rusted steel bar 11, which significantly improves the corrosion resistance of the steel bar 11 and extends the service life of the reinforced concrete 10 structure. This method is simple to operate, highly economical, does not damage the concrete structure, does not affect the structural safety, and has a strong application value.

[0064] It should be noted that when processing the exposed steel bars 11 in the actual structure, a method of connecting the exposed steel bars 11 with a wire can be used instead of the immersion method in the above test. By installing a wire on the exposed steel bars 11 and connecting the wire to the negative electrode of the power supply 300 and the configured solution, an electrochemical system is established. In this case, the current will flow through the exposed steel bars 11 through the wire, prompting the steel bars 11 to achieve in-situ generation of a metal hydroxide coating.

[0065] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. An in-situ preparation method of a steel bar corrosion-resistant coating based on electrochemical realkalinization, characterized in that: include: S1: preparing an oxygen-rich aqueous solution (100); S2: preparing a mixed solution (200) rich in divalent metal salt and trivalent metal salt; S3: connecting the steel bars (11) in the reinforced concrete (10) to the negative electrode of a direct current power source (300), connecting the titanium mesh (400) in the oxygen-rich aqueous solution (100) to the positive electrode of the direct current power source (300), and performing a re-alkalization treatment through electrochemistry to form an alkaline environment on the surface of the steel bars (11) confirmed to be corroded; S4: replacing the oxygen-rich aqueous solution (100) with the mixed solution (200), and forming a metal hydroxide coating in situ on the surface of the steel bars (11) confirmed to be corroded in the reinforced concrete (10) under the action of the electrostatic field.

2. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1 is characterized in that: In S1, the preparation of the oxygen-enriched aqueous solution (100) comprises: using a bubbler to continuously pass air into the ice-water mixture, and using a dissolved oxygen meter to test the oxygen content in the solution until the oxygen content in the solution reaches a preset oxygen content.

3. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 2 is characterized in that: The preset oxygen content of the oxygen-rich aqueous solution (100) is greater than or equal to 10 mg / L.

4. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1, characterized in that: In S2, the concentration ratio of the divalent metal salt to the trivalent metal salt in the mixed solution (200) is greater than or equal to 3:

1.

5. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1, characterized in that: In S2, the divalent metal salt is selected from at least one of magnesium sulfate and zinc sulfate, and the trivalent metal salt is selected from at least one of aluminum nitrate and iron nitrate.

6. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1 is characterized in that: In S3, the voltage used in the electrochemical realkalification is in the range of 15 to 30 V, and the duration of the electrochemical realkalification is 2 to 3 days.

7. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1 is characterized in that: In S3, during the electrochemical realkalinization process, the chemical reaction formula on the surface of the steel bar (11) is: O2+2H2O+4e→4OH - ; Among them, e is a negative electron.

8. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1, characterized in that: In S4, when the pH value in the concrete (12) is greater than or equal to 12, the oxygen-enriched aqueous solution (100) is replaced with the mixed solution (200).

9. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1, characterized in that: In S4, the voltage range of the electrostatic field is 15 to 30 V, and the duration of the electrostatic field is 3 to 5 days.

10. The in-situ preparation method of steel bar corrosion resistant coating based on electrochemical realkalinization according to claim 1, characterized in that: In S4, under the action of the electrostatic field, the metal ions in the solution migrate to the surface of the steel bar (11) confirmed to be corroded and form the metal hydroxide coating. The reaction process of the metal hydroxide coating is: Among them, M 2+ is a divalent metal ion, M 3+ is a trivalent metal ion, x is a natural number, and y is a natural number.

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