Preparation method of temperature-controlled repair type phytic acid conversion film

Abstract

This invention discloses a method for preparing a temperature-controlled repairable phytic acid conversion film, belonging to the field of steel reinforcement corrosion prevention. First, the steel reinforcement is immersed in a phytic acid solution for a certain period of time and then removed. After curing, the steel reinforcement with the deposited phytic acid conversion film is immersed in a solution containing metal-organic framework-loaded corrosion inhibitors (MOFs-CI) for further immersion. Different temperatures are set during immersion to control the release rate of the corrosion inhibitor in the MOFs. At a suitable release rate, the released corrosion inhibitor precisely matches the needs of different parts, achieving excellent repair effects. This greatly solves the problem of cracks appearing in the phytic acid conversion film on the metal surface, leading to chloride ion corrosion of the steel reinforcement.

Description

Technical Field

[0001] This invention relates to the field of rust prevention for reinforcing steel bars, and specifically to a method for preparing a temperature-controlled repair type phytic acid conversion membrane. Background Technology

[0002] Steel reinforcement corrosion can easily lead to cracking and reduced strength in concrete structures, and in severe cases, it can even cause the concrete structure to collapse, resulting in significant loss of life and property. Therefore, researchers in related fields have been conducting research on how to improve the corrosion resistance of steel reinforcement.

[0003] Phytic acid conversion coatings are a common corrosion protection method in the field of metal corrosion protection. They involve immersing the metal in a phytic acid solution for a period of time, after which the phytic acid molecules chelate with metal ions, depositing a corrosion-protective phytic acid conversion coating on the metal surface. In recent years, phytic acid conversion coatings have also begun to be applied to reinforced concrete environments.

[0004] However, after drying and forming, the phytic acid conversion film formed on the metal surface is prone to cracking, and these cracks often become the entry point for chloride ions to corrode the steel bars. To reduce cracks on the surface of the phytic acid film, researchers often start by changing the composition or related parameters of the phytic acid film. However, based on numerous studies, this improvement method is often not ideal. This is because the appearance of cracks is mainly caused by the internal tension of the phytic acid film during the drying process, which is an inherent physicochemical property, and it is difficult to completely avoid the occurrence of cracks in the phytic acid film through various modification methods.

[0005] Furthermore, this invention focuses on an important characteristic of phytic acid conversion membranes, namely that the cracks mainly contain two areas: (1) when the phytic acid conversion membrane is severely cracked, the reinforcing steel substrate at the crack is exposed; (2) after the phytic acid conversion membrane cracks, a phytic acid membrane fracture appears at the fracture point of the membrane layer. Therefore, this invention changes the technical approach, not starting from reducing phytic acid membrane cracks, but allowing the cracks to form naturally, and then introducing a rust inhibitor commonly used in reinforced concrete to repair the phytic acid membrane after the cracks have formed. Summary of the Invention

[0006] To address the problems existing in the prior art, the objective of this invention is to develop a temperature-controlled MOFs-based slow-release rust-inhibiting and repairing phytate conversion film based on the different characteristics of the two regions of phytate film cracks on the steel reinforcement surface. The release rate of the rust inhibitor in the MOFs is controlled by adjusting the temperature.

[0007] In the first stage, the primary objective is to repair exposed rebar. This stage focuses on repairing the exposed rebar. Adding all the rust inhibitors to the solution simultaneously would result in localized areas with excessive rust inhibitor adsorption, while other areas would have very little adsorption, leading to an uneven rust-inhibiting film on the rebar surface. Therefore, in the first stage, low-temperature control is used to ensure a regular, slow release of the rust inhibitor from the MOF (Metal-Oxide-Foil). This drives the adsorption and growth of the rust inhibitor film on the rebar surface while the MOF continuously provides a low concentration of rust inhibitor, ensuring the formation of a dense and uniform rust-inhibiting film. In the second stage, the focus is on repairing cracks in the phytic acid film. This stage targets the phytic acid conversion film itself, essentially "filling in" the cracks. Since the second stage does not involve direct contact between the rust inhibitor and the rebar, and the cracked area is much larger than the rust inhibitor's molecular size, it is appropriate to increase the solution temperature in the second stage to accelerate the release rate, allowing a large amount of rust inhibitor to accumulate at the cracks in a short time.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a temperature-controlled repair-type phytic acid conversion film for corrosion protection of reinforcing steel bars, comprising the following steps:

[0009] Step (1) Preparation of phytic acid conversion membrane:

[0010] First, immerse the steel bars in phytic acid solution for 600-2000 seconds, then remove them. After immersion, cure them in air at a temperature of 20±1℃ and a humidity of 50±5% for 0.5-6 hours to obtain a phytic acid conversion film on the surface of the steel bars.

[0011] Step (2) Preparation of the supported corrosion inhibitor MOFs-CI:

[0012] First, the MOF materials were dried at 200℃ for 8 hours to dehydrate them. Then, the MOF materials were added to a methanol solution containing a rust inhibitor and stirred at a constant speed under the control of a magnetic stirrer. After centrifugation of the MOF-methanol solution, the MOF materials were removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0013] Step (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0014] MOFs-CI was dissolved in deionized water to prepare a MOFs-CI solution. Then, the steel bars with the phytic acid conversion film prepared in step (1) were immersed in the MOFs-CI solution. During the immersion process, different temperatures were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI. After immersion, the steel bars were removed and cured in air at a temperature of 20±1℃ and a humidity of 50±5% for 5 hours, resulting in a temperature-controlled repaired phytic acid conversion film on the surface of the steel bars.

[0015] Furthermore, the phytic acid solution described in step (1) is composed of phytic acid and deionized water, and the mass concentration of phytic acid in the solution is 1-2%.

[0016] Furthermore, the pH of the solution described in step (1) is adjusted by a 0.5M NaOH solution, and the pH is controlled between 3 and 5.

[0017] Furthermore, the MOFs material used in step (2) is specifically classified as ZIF-8 or MOF-5.

[0018] Further, in step (2), the mass concentration of MOFs material in methanol solution is 0.1% to 1%; the rust inhibitor added to methanol solution is triethanolamine or benzotriazole, and the mass concentration of the rust inhibitor in methanol solution is 1% to 5%.

[0019] Furthermore, the stirring process described in step (2) involves stirring at a constant speed with a magnetic stirrer for 8 to 24 hours.

[0020] Furthermore, the MOFs-CI solution described in step (3) has a MOFs-CI mass concentration of 0.1% to 1%.

[0021] Furthermore, in step (3), the steel bars with phytic acid conversion film deposited are immersed in MOFs-CI solution for 12 to 48 hours; the temperature range is set to 25℃ to 60℃, and the release rate of the rust inhibitor is controlled by setting different temperatures.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1. Traditional phytic acid conversion membrane (HACCP) protective layers are prone to cracking, leading to a decline in their corrosion resistance. This invention addresses the cracks in the HACCP on the rebar surface, differentiating between the exposed rebar area and the cracked membrane area based on the specific crack conditions. By combining with MOFs (Metal-Oxide-Foil) slow-release corrosion inhibitors, the release process of the corrosion inhibitors is controlled, allowing for phased and orderly release and film formation. In fact, the corrosion inhibitor plays a dual role here. In the first stage, the corrosion inhibitor functions as a corrosion inhibitor, with its concentration in the solution gradually increasing under continuous release. The corrosion inhibitor preferentially contacts the rebar surface directly, forming a corrosion-inhibiting film layer. In the second stage, after a sufficient corrosion-inhibiting film layer has formed on the rebar surface, the corrosion inhibitor functions as a healing agent, adsorbing at the cracks through the controlled slow release of MOFs, effectively filling the phytic acid membrane cracks. This MOFs slow-release repair method first forms a complete corrosion-inhibiting film layer on the rebar surface, and then acts as a healing agent to effectively fill the cracks.

[0024] 2. In traditional research, technicians often try to reduce cracks in phytic acid films by adjusting experimental parameters and adding other functional materials. However, these methods are often not very effective. This invention changes the approach, focusing not on reducing cracks in the phytic acid film, but on using temperature-controlled MOF rust inhibitor release to perform temperature-controlled repair of the cracks.

[0025] 3. Among the numerous cracks on the surface of the phytic acid membrane, the crack conditions are not entirely the same, mainly falling into two categories. One category involves cracks that directly expose the reinforcing steel substrate, while the other involves cracks that have not yet exposed the substrate. Based on the above two points, it has been demonstrated that MOFs slow-release repair can effectively solve the problem of cracks in exposed reinforcing steel. For phytic acid membranes without exposed reinforcing steel, the MOF-Cl in this invention can also effectively repair cracks in stages at two temperature levels. Therefore, the repair technology in this invention can achieve good repair effects for different types of phytic acid membrane cracks. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the open circuit potential of the temperature-controlled repair type phytic acid conversion membrane in this embodiment.

[0027] Figure 2 This is a schematic diagram of the corrosion current density of the temperature-controlled repair type phytic acid conversion membrane in this embodiment. Detailed Implementation

[0028] To better explain the present invention, the technical solution of the present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] (1) Preparation of phytic acid conversion membrane:

[0031] A phytic acid solution with a mass concentration of 1% was prepared. The pH of the solution was adjusted to 3 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 600 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 0.5 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0032] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0033] First, the MOF-5 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing triethanolamine rust inhibitor at a concentration of 1%; the mass concentration of the MOF material in the methanol solution was 0.1%. The mixture was stirred at a constant speed for 8 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0034] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0035] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 0.1%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 12 hours. Temperatures of 25°C and 35°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 25°C temperature was applied for 4 hours, and the 35°C temperature for 8 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in a temperature-controlled repair phytic acid conversion film on the steel bar surface.

[0036] Example 2

[0037] (1) Preparation of phytic acid conversion membrane:

[0038] A phytic acid solution with a mass concentration of 1.5% was prepared. The pH of the solution was adjusted to 4 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 1200 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 3 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0039] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0040] First, the MOF-5 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing triethanolamine rust inhibitor at a concentration of 3%; the mass concentration of the MOF material in the methanol solution was 0.5%. The mixture was stirred at a constant speed for 16 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0041] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0042] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 0.5%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 24 hours. Temperatures of 25°C and 45°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 25°C temperature was applied for 8 hours, and the 45°C temperature for 16 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in a temperature-controlled, repairable phytic acid conversion film on the steel bar surface.

[0043] Example 3

[0044] (1) Preparation of phytic acid conversion membrane:

[0045] A phytic acid solution with a mass concentration of 2% was prepared. The pH of the solution was adjusted to 5 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 2000 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 6 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0046] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0047] First, the ZIF-8 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing triethanolamine rust inhibitor at a concentration of 5%; the mass concentration of the MOF material in the methanol solution was 1%. The mixture was stirred at a constant speed for 24 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0048] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0049] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 1%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 36 hours. Temperatures of 25°C and 60°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 25°C temperature was applied for 12 hours, and the 60°C temperature for 24 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in a temperature-controlled, repairable phytic acid conversion film on the steel bar surface.

[0050] Example 4

[0051] (1) Preparation of phytic acid conversion membrane:

[0052] A phytic acid solution with a mass concentration of 1% was prepared. The pH of the solution was adjusted to 3 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 600 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 0.5 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0053] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0054] First, the MOF-5 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing benzotriazole rust inhibitor at a concentration of 1%; the mass concentration of the MOF material in the methanol solution was 0.1%. The mixture was stirred at a constant speed for 8 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0055] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0056] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 0.1%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 48 hours. Temperatures of 35°C and 60°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 35°C temperature was applied for 16 hours, and the 60°C temperature for 32 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in a temperature-controlled repair phytic acid conversion film on the steel bar surface.

[0057] Example 5

[0058] (1) Preparation of phytic acid conversion membrane:

[0059] A phytic acid solution with a mass concentration of 1.5% was prepared. The pH of the solution was adjusted to 4 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 1200 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 3 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0060] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0061] First, the ZIF-8 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing benzotriazole rust inhibitor at a concentration of 3%; the mass concentration of the MOF material in the methanol solution was 0.5%. The mixture was stirred at a constant speed for 16 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0062] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0063] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 0.5%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 12 hours. Temperatures of 30°C and 60°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 30°C temperature was applied for 4 hours, and the 60°C temperature for 8 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in steel bars with a temperature-controlled repair phytic acid conversion film on their surface.

[0064] Example 6

[0065] (1) Preparation of phytic acid conversion membrane:

[0066] A phytic acid solution with a mass concentration of 2% was prepared. The pH of the solution was adjusted to 5 using a 0.5M NaOH solution. The steel bars were then immersed in the solution for 2000 seconds and then removed. After curing in air at a temperature of 20±1℃ and a humidity of 50±5% for 6 hours, a phytic acid conversion film was obtained on the surface of the steel bars.

[0067] (2) Preparation of MOFs-CI loaded with rust inhibitor:

[0068] First, the ZIF-8 type MOF material was dried at 200℃ for 8 hours to dehydrate it. Then, the MOF material was added to a methanol solution containing benzotriazole rust inhibitor at a concentration of 5%; the mass concentration of the MOF material in the methanol solution was 1%. The mixture was stirred at a constant speed for 24 hours under the control of a magnetic stirrer. After centrifugation, the MOF material was removed and vacuum dried at 100℃ for 5 hours to remove residual solvent, yielding the desired MOF-CI.

[0069] (3) Preparation of temperature-controlled repair type phytic acid conversion membrane:

[0070] MOFs-CI was added to deionized water to prepare a MOFs-CI solution with a mass concentration of 1%. Then, the steel bars with the phytic acid conversion film prepared in step one were immersed in the MOFs-CI solution for 24 hours. Temperatures of 25°C and 45°C were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI; the 25°C temperature was applied for 8 hours, and the 45°C temperature for 16 hours. After immersion, the steel bars were removed and cured in air at 20±1°C and 50±5% humidity for 5 hours, resulting in steel bars with a temperature-controlled repair phytic acid conversion film on their surface.

[0071] Comparative Example 1

[0072] Following the method in step one of Example 3, a phytic acid conversion film was deposited on the surface of the steel bar (steps two and three were not performed).

[0073] Comparative Example 2

[0074] Following the method in Example 3, a phytic acid conversion film was deposited on the surface of the reinforcing steel (in step three, the reinforcing steel with the phytic acid conversion film was simply soaked in MOF-Cl solution for 36 hours without temperature control; the remaining steps were the same as in Example 3).

[0075] Rust-inhibiting performance evaluation:

[0076] The temperature-controlled repair type phytic acid conversion coating on steel bars was immersed in a simulated concrete solution containing sodium chloride. The base of the simulated solution was a calcium hydroxide solution with a pH of 11.5, and the sodium chloride concentration in the simulated solution was 6%. The immersion time was 21 days. The corrosion inhibition capacity was then qualitatively and quantitatively studied using electrochemical methods. Tests were conducted according to the experimental procedures described above, and the corrosion potential and corrosion current density were obtained.

[0077] from Figure 1The open-circuit potential data show that the open-circuit potential of the temperature-controlled repair conversion film is significantly higher than that of the unrepaired sample (Comparative Example 1) and the sample without temperature-controlled repair technology (Comparative Example 2). This indicates that the temperature-controlled staged repair technology proposed in this invention can effectively repair the corrosion defects caused by cracking of the phytic acid conversion film and effectively improve its corrosion resistance. Figure 2 The corrosion current density data show that the corrosion current density of the sample treated with temperature-controlled repair technology is significantly lower than that of the control sample at all corrosion ages, proving that the temperature-controlled repair type anti-corrosion conversion film has superior anti-corrosion performance.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a temperature-controlled phytic acid conversion membrane, characterized in that, Includes the following steps: Step (1) Preparation of phytic acid conversion membrane: First, immerse the steel bars in phytic acid solution for 600-2000 seconds and then remove them. After immersion, cure them in air at a temperature of 20±1℃ and a humidity of 50±5% for 0.5-6 hours to obtain a phytic acid conversion film on the surface of the steel bars. Step (2) Preparation of the supported corrosion inhibitor MOFs-CI: First, the metal-organic framework (MOF) materials were dried at 200°C for 8 hours to dehydrate them. Then, the MOF materials were added to a methanol solution containing a rust inhibitor and stirred at a constant speed under the control of a magnetic stirrer. After centrifugation, the MOF materials were removed and vacuum dried at 100°C for 5 hours to remove the remaining solvent, thus obtaining the desired MOFs-CI. Step (3) Preparation of temperature-controlled repair type phytic acid conversion membrane: MOFs-CI was placed in deionized water to prepare a MOFs-CI solution. Then, the steel bar with phytic acid conversion film prepared in step (1) was immersed in the MOFs-CI solution. During the immersion process, different temperatures were applied to the MOFs-CI solution to control the slow release process of the rust inhibitor by MOFs-CI. After immersion, the steel bar was taken out and cured in air at a temperature of 20±1℃ and a humidity of 50±5% for 5 hours to obtain a temperature-controlled repair type phytic acid conversion film on the surface of the steel bar.

2. The method for preparing a temperature-controlled phytic acid conversion membrane according to claim 1, characterized in that: In step (1), the phytic acid solution is composed of phytic acid and deionized water, and the mass concentration of phytic acid in the solution is 1-2%.

3. The method for preparing a temperature-controlled repair-type phytic acid conversion membrane according to claim 1, characterized in that: In step (1), the pH of the phytic acid solution is adjusted by 0.5M NaOH solution, and the pH is controlled between 3 and 5.

4. The method for preparing a temperature-controlled repair-type phytic acid conversion membrane according to claim 1, characterized in that: In step (2), the MOFs material used is specifically ZIF-8 or MOF-5.

5. The method for preparing a temperature-controlled phytic acid conversion membrane according to claim 1, characterized in that: In step (2), the mass concentration of MOFs material in methanol solution is 0.1% to 1%; the rust inhibitor added to methanol solution is triethanolamine or benzotriazole, and the mass concentration of the rust inhibitor in methanol solution is 1% to 5%.

6. The method for preparing a temperature-controlled phytic acid conversion membrane according to claim 1, characterized in that: In step (2), the stirring time with a magnetic stirrer at a constant speed is 8 to 24 hours.

7. The method for preparing a temperature-controlled repair-type phytic acid conversion membrane according to claim 1, characterized in that: In step (3), the mass concentration of MOFs-CI in the MOFs-CI solution is 0.1% to 1%.

8. The method for preparing a temperature-controlled repair-type phytic acid conversion membrane according to claim 1, characterized in that: In step (3), the steel bars with phytic acid conversion film deposited are immersed in MOFs-CI solution for 12 to 48 hours; the temperature range is set to 25℃ to 60℃, and the release rate of the rust inhibitor is controlled by setting different temperatures.

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