Metakaolin geopolymer anticorrosive paint and preparation method thereof

Abstract

The preparation method comprises the following steps: preparing a pre-prepared mixed solution, namely uniformly mixing a phosphoric acid exciting agent and deionized water according to a certain proportion, adding a certain amount of dimethyl silicone oil and a silane coupling agent, and uniformly stirring and mixing to obtain the pre-prepared mixed solution; and preparing slurry: adding a certain amount of metakaolin into the pre-prepared mixed solution, and uniformly stirring to obtain a coating finished product. Hydrophobic modification is carried out on the geopolymer through the dimethyl silicone oil, pores are filled, the porosity of the coating is reduced, corrosion medium permeation is blocked, and the protection service life is prolonged. The hydrophobic property and chemical inertness of the simethicone are utilized to endow the coating with high barrier property to corrosive media such as water, acid and salt, and the coating is suitable for severe environments such as ocean engineering.

Description

Technical Field

[0001] The present invention relates to a metakaolin-based geopolymer anti-corrosion coating and a preparation method thereof, belonging to the technical field of functional building materials. Background Art

[0002] Reinforced concrete is the main material in current construction projects. However, its corrosion resistance has always been a problem that the engineering community has been continuously concerned about. Especially for reinforced concrete used in marine environments, seawater contains a large number of ions that are corrosive to concrete structures, such as SO24-, Mg2+, Cl-, etc. Among them, chloride ions have a small radius and strong penetration ability, and can penetrate deep into the structure through the pores and microcracks of concrete. When the chloride ion concentration reaches a certain threshold, it will damage the passivation film on the surface of the steel bars, triggering the electrochemical corrosion reaction of the steel bars. This corrosion process will not only reduce the cross-sectional area of the steel bars, but also generate internal stress on the concrete protective layer due to the volume expansion of the corrosion products, thereby causing deterioration phenomena such as concrete cracking and spalling.

[0003] Currently, the solution to this problem is to coat a protective layer on the surface of reinforced concrete to improve the anti-corrosion performance through the barrier of the coating. The existing composite coatings are divided into organic-inorganic hybrid coatings, nano-composite coatings, etc. The dispersion process of nano-composite coatings is complex and the cost is high. The organic-inorganic hybrid coatings have poor compatibility, large polarity differences between organic and inorganic components, and are prone to phase separation. Currently, there is also a solution to use metakaolin-based geopolymer as a coating. However, traditional metakaolin-based geopolymers (such as silicate-aluminate systems) are prone to form micropores and cracks during the curing process, resulting in corrosion media (such as water, Cl - 、SO4 2- etc.) are easily permeated through the pores to the surface of the substrate, and the long-term protection effect decreases. The surface of unmodified geopolymer has strong hydrophilicity (contact angle <90°), and it is difficult to effectively block water vapor, resulting in the coating being prone to corrosion and peeling in a humid environment. Therefore, it is necessary to find a method to solve the above problems. Summary of the Invention

[0004] Aiming at the deficiencies of the above-mentioned prior art, the present invention provides an anti-corrosion geopolymer coating and a preparation method thereof. The specific purposes include: hydrophobic modification of the geopolymer with dimethyl silicone oil, filling pores and reducing the porosity of the coating, blocking the penetration of corrosion media, and extending the protection life. Utilize the hydrophobic property and chemical inertness of dimethyl silicone oil to endow the coating with high barrier performance against corrosion media such as water, acid, and salt, and is suitable for harsh environments such as marine engineering. The one-step blending method is used to directly introduce dimethyl silicone oil into the geopolymer precursor activation solution, avoiding the use of multi-step reactions and reducing the energy consumption and environmental pollution risks.

[0005] One of the objectives of the present invention is to provide a metakaolin-based geopolymer anti-corrosion coating, which comprises the following components by mass fraction: 15-30 parts of a phosphoric acid activator, 1-4 parts of dimethyl silicone oil, 0.01-0.1 part of a silane coupling agent, 40-60 parts of metakaolin, and 20-50 parts of deionized water.

[0006] Further, it comprises the following components by mass fraction: 28 parts of a phosphoric acid activator, 1 part of dimethyl silicone oil, 0.04 part of a silane coupling agent, 50 parts of metakaolin, and 20 parts of deionized water.

[0007] Further, the ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is (1-2):1.

[0008] A preparation method of a metakaolin-based geopolymer anti-corrosion coating comprises the following steps:

[0009] (1) Prepare a prefabricated mixture: Take a certain proportion of the phosphoric acid activator and deionized water, mix them evenly, then add a certain amount of dimethyl silicone oil and silane coupling agent, and stir and mix evenly to obtain the prefabricated mixture;

[0010] (2) Prepare a slurry: Add a certain amount of metakaolin to the prefabricated mixture obtained in step (1), and stir evenly to obtain the finished coating.

[0011] Further, in step (1), the ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is 1.4.

[0012] Further, the addition amount of the dimethyl silicone oil is 1%-6% of the mass of metakaolin, and the addition amount of the silane coupling agent is 4% of the dosage of the dimethyl silicone oil.

[0013] Further, the uniform stirring is to continuously stir the slurry at 300 r / min at room temperature for 10 min to obtain the finished coating.

[0014] In this application, an acid-activated geopolymer is used. Geopolymer refers to all three-dimensional network gels prepared from natural minerals or solid waste, which are composed of silicon-oxygen tetrahedrons and aluminum-oxygen tetrahedrons polymerized to have amorphous and quasi-crystalline characteristics. Its three-dimensional network structure is composed of [SiO4]4- and [AlO4]5- tetrahedrons alternately connected by covalent bonds, and has the advantages of fire resistance, chemical corrosion resistance, high mechanical strength, and good durability. The reaction process of the acid-activated geopolymer is divided into depolymerization and polycondensation. In the depolymerization process, H+ in phosphoric acid decomposes the Al-O layer, and the excess H+ reacts with the dissolved H10Si4O13 to form [Si4O13H11]. In the polycondensation process, [Si4O13H11] formed in the depolymerization step is connected with Al3-, H+, and PO43- in the phosphoric acid solution to form structural units such as -Al-O-P-O- and -Si-O-Al-O-P-O-. The structural units are connected by hydrogen bonds to form a three-dimensional network structure.

[0015] In this application, a hydrophobic substance, dimethyl silicone oil, is added to the geopolymer. After mixing with the geopolymer, the wetting angle changes, making it less easy for water to penetrate. Moreover, dimethyl silicone oil can fill the porosity, reducing the porosity and preventing water from seeping into the interior to protect the substrate. The addition of silane coupling agent makes the combination of dimethyl silicone oil and kaolin better, forming a hydrophobic layer and blocking the pores, forming a hydrophobic layer on the surface, changing the wetting angle, and optimizing the hydrophobic effect.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. By incorporating dimethyl silicone oil, the three-dimensional network structure of the geopolymer is filled and modified, reducing the porosity of the geopolymer and increasing the sealing effect of the coating.

[0018] 2. The hydrophobic methyl groups (-CH3) contained in dimethyl silicone oil are enriched on the surface of the coating, replacing the original hydrophilic groups (-OH), forming a gradient hydrophobic layer, significantly reducing the surface energy, inhibiting the infiltration of water molecules, and the corrosion potential and corrosion current measured by the electrochemical workstation are significantly modified, and the corrosion performance is excellent.

[0019] 3. The construction method is simple, economical, and has high construction efficiency. Specific embodiments

[0020] In order to enable those skilled in the art to better understand the technical solutions in this application, the following will clearly and completely describe the technical solutions in combination with the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments, and do not limit the protection scope of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of this application. Any modifications, equivalent replacements, etc. made within the spirit and scope of the present invention shall be included within the protection scope of the present invention.

[0021] In the description of this application, the meaning of "a variety of" is two or more, unless otherwise clearly and specifically defined.

[0022] One specific embodiment of the present invention lies in a metakaolin-based geopolymer anti-corrosion coating, which comprises the following components in mass fractions: 15-30 parts of a phosphoric acid activator, 1-4 parts of dimethyl silicone oil, 0.01-0.1 part of a silane coupling agent, 40-60 parts of metakaolin, and 20-50 parts of deionized water.

[0023] Further, the phosphorus-aluminum ratio is 1.3, water / metakaolin = 0.4, the curing time is 7 days, the ratio of dimethyl silicone oil to metakaolin is 1%-6%, and the ratio of the silane coupling agent to dimethyl silicone oil = 4%.

[0024] Further, the ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is (1-2):1.

[0025] A preparation method of a metakaolin-based geopolymer anti-corrosion coating comprises the following steps:

[0026] (1) Prepare a prefabricated mixture: Take a certain proportion of the phosphoric acid activator and deionized water, mix them evenly, and then add a certain amount of dimethyl silicone oil and silane coupling agent, and stir and mix evenly to obtain a prefabricated mixture;

[0027] (2) Prepare a slurry: Add a certain amount of metakaolin to the prefabricated mixture obtained in step (1), and stir evenly to obtain the coating finished product.

[0028] Further, in step (1), the ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is 1.4.

[0029] Further, the addition amount of the dimethyl silicone oil is 1%-6% of the mass of metakaolin, and the addition amount of the silane coupling agent is 4% of the dosage of the dimethyl silicone oil.

[0030] Further, the uniform stirring is to continuously stir the slurry at 300 r / min at room temperature for 10 min to obtain the coating finished product.

[0031] The specific embodiments are as follows:

[0032] Example 1

[0033] Step 1: Add 28.30 g of 85% phosphoric acid to 20.75 g of deionized water, mechanically stir and mix evenly, and cool to room temperature to prepare a prefabricated mixed solution.

[0034] Step 2: Add 50 g of metakaolin to the prefabricated mixed solution, continuously stir at 300 r / min at room temperature for 10 min to obtain a modified geopolymer slurry. Apply the geopolymer slurry evenly on the protected bottom plate and cure for 7 days until the coating is formed.

[0035] Example 2

[0036] Step 1: Add 28.30 g of 85% phosphoric acid to 20.75 g of deionized water, mechanically stir and mix evenly, and cool to room temperature to prepare a prefabricated mixed solution.

[0037] Step 2: Add 1 g of dimethyl silicone oil and 0.04 g of silane coupling agent to the solution and mechanically stir to prepare a prefabricated mixed solution.

[0038] Step 3: Add 50 g of metakaolin to the prefabricated mixed solution, continuously stir at 300 r / min at room temperature for 10 min to obtain a modified geopolymer slurry. Apply the geopolymer slurry evenly on the protected bottom plate and cure for 7 days until the coating is formed.

[0039] Example 3

[0040] Step 1: Add 28.30 g of 85% phosphoric acid to 20.75 g of deionized water, mechanically stir and mix evenly, and cool to room temperature to prepare a prefabricated mixed solution.

[0041] Step 2: Add 2 g of dimethyl silicone oil and 0.08 g of silane coupling agent to the solution and mechanically stir to prepare a prefabricated mixed solution.

[0042] Step 3: Add 50 g of metakaolin to the prefabricated mixed solution, continuously stir at 300 r / min at room temperature for 10 min to obtain a modified geopolymer slurry. Apply the geopolymer slurry evenly on the protected bottom plate and cure for 7 days until the coating is formed.

[0043] Example 4

[0044] Step 1: Add 28.30 g of 85% phosphoric acid to 20.75 g of deionized water, mechanically stir and mix evenly, and cool to room temperature to prepare a prefabricated mixed solution.

[0045] Step 2: Add 3 g of dimethyl silicone oil and 0.12 g of silane coupling agent to the solution and mechanically stir to prepare a prefabricated mixed solution.

[0046] Step 3: Add 50 g of metakaolin to the prefabricated mixture, continuously stir at 300 r / min at room temperature for 10 min to obtain a modified geopolymer slurry, evenly apply the geopolymer slurry on the protected bottom plate, and cure for 7 days until the coating is formed.

[0047]

[0048] As can be seen from the above, the water absorption rate of the modified geopolymer is 0.99%-2.16%, and the decrease compared with the unmodified one is 30%-68%. The contact angle is 117.1°-135.2°, and the increase compared with the unmodified one is 398%-475%. The corrosion potential is -534.94 mV--531.48 mV, and the increase compared with the unmodified one is 7.7%-8.3%. The corrosion current is 0.347×10 - 2 mA / cm 2 -3.72×10 -2 mA / cm 2 , and the decrease compared with the unmodified one is 19%-92%. The best scheme is Example 4.

[0049] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A metakaolin-based geopolymer anti-corrosion coating, characterized in that, It comprises components in the following mass fractions: 15 - 30 parts of phosphoric acid activator, 1 - 4 parts of dimethyl silicone oil, 0.01 - 0.1 part of silane coupling agent, 40 - 60 parts of metakaolin, and 20 - 50 parts of deionized water.

2. The geopolymer anti-corrosion coating made of metakaolin according to claim 1, characterized in that, The ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is (1 - 2):

1.

3. A preparation method of a metakaolin-based geopolymer anti-corrosion coating, characterized in that, It includes the following steps: (1) Prepare a pre - mixed solution: Take a certain proportion of phosphoric acid activator and deionized water, mix them evenly, then add a certain amount of dimethyl silicone oil and silane coupling agent, and stir and mix evenly to obtain a pre - mixed solution; (2) Prepare a slurry: Add a certain amount of metakaolin to the pre - mixed solution obtained in step (1), and stir evenly to obtain the finished coating.

4. The preparation method of a metakaolin-based geopolymer anti-corrosion coating according to claim 1, characterized in that: In step (1), the ratio of phosphoric acid in the phosphoric acid activator to alumina in metakaolin is 1.

4.

5. The preparation method of a metakaolin-based geopolymer anti-corrosion coating according to claim 3, characterized in that: The addition amount of the dimethyl silicone oil is 1% - 6% of the mass of metakaolin, and the addition amount of the silane coupling agent is 4% of the dosage of the dimethyl silicone oil.

6. The preparation method of a metakaolin-based geopolymer anti-corrosion coating according to claim 3, characterized in that: In step (2), the "stir evenly" means continuously stirring the slurry at 300 r / min at room temperature for 10 min to obtain the finished coating.

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