A graphene oxide geopolymer coating and its preparation method and application

Abstract

The present invention provides a graphene oxide geopolymer coating and a preparation method and application thereof, wherein the raw materials thereof include the following components: slag, fly ash, water, an activator, a water reducing agent, a defoaming agent, graphene oxide, acrylic emulsion, nano titanium dioxide and phenylethylamine. The geopolymer coating of the present invention uses slag and fly ash as gel materials, and modifies them by adding graphene oxide to slow down the shrinkage and cracking of the coating; an activator with a low water glass modulus is used to adapt to the activation of slag and fly ash as gel materials, so as to avoid problems such as alkali efflux and severe shrinkage of the geopolymer; the amine group in the phenylethylamine can not only react with the active functional group in the geopolymer matrix to form a covalent bond, but also react with the carboxyl group and epoxy group on the surface of the graphene oxide to form a stable covalent bond, and the two are more closely cross-linked due to the addition of phenylethylamine, thereby further improving the anti-corrosion and various performances.

Description

Technical Field

[0001] The present invention relates to the technical field of anti-corrosion coating materials, and in particular to a graphene oxide geopolymer coating and a preparation method and application thereof. Background Art

[0002] Reinforced concrete structures are widely used in many fields such as water conservancy projects, bridges and tunnels, and have become the most widely used building form. One of the main factors that reduce the durability of reinforced concrete structures is steel corrosion, especially in environments with high humidity and high concentration of corrosive media such as water conservancy projects and marine projects. The rust expansion damage of reinforced concrete structures is particularly serious. The rust generated after the steel bars rust fills the gap between the concrete and the steel bars, and the volume of rust is larger, so a large rust expansion stress is generated, resulting in cracking damage. The cracks generated allow the corrosive media to directly enter the surface of the steel bars, further accelerating the corrosion of the steel bars, seriously affecting the performance of the structure and reducing its normal working life.

[0003] The application of coating protection measures in reinforced concrete over the past few decades has shown that it has a highly effective protective effect. At the same time, its greater economic efficiency makes it have a broad prospect in the field of steel bar corrosion protection. At this time, inorganic coatings as a kind of building material have gradually come into everyone's attention. Compared with organic coatings, inorganic coatings have the advantages of high strength, high temperature resistance, corrosion resistance, good air permeability, and non-toxicity. The solvent of inorganic coatings is mainly water, while the components of organic coatings are mostly organic substances such as aldehydes and ketones. Therefore, inorganic coatings are more in line with the advantages of water-based, harmless, and simplified coatings advocated by people.

[0004] Although alkali-activated coatings are more compatible with concrete due to their own material properties, the use of alkaline solutions of different concentrations will result in different effects on the coatings. Excessively high concentrations of activation will cause the coating to have alkaline efflorescence on the surface, thus affecting the appearance. More importantly, due to the large autogenous shrinkage of geopolymers, cracks may form in the geopolymer coating due to shrinkage during the curing process. These cracks may reduce its overall toughness and crack resistance, ultimately affecting its anti-corrosion performance during use, resulting in the application of geopolymers in anti-corrosion coatings being limited. Summary of the invention

[0005] Based on this, it is necessary to provide a graphene oxide geopolymer coating with good anti-corrosion performance.

[0006] A graphene oxide geopolymer coating comprises the following raw materials, measured by weight: 35-40 parts of slag, 20-25 parts of fly ash, 20-25 parts of water, 10-15 parts of activator, 0.9-1.2 parts of water reducer, 1.5-2.7 parts of defoamer, 0.02-0.04 parts of graphene oxide, 1-2 parts of acrylic emulsion, 1-2 parts of nano titanium dioxide and 0.8-1.2 parts of phenylethylamine.

[0007] In one embodiment, the activator is composed of sodium hydroxide and water glass, and the modulus of the water glass is 1 to 1.5, preferably 1 to 1.2.

[0008] In one embodiment, the mass ratio of the sodium hydroxide to the water glass is 1:4-6.

[0009] In one embodiment, the water reducing agent is a polycarboxylic acid water reducing agent.

[0010] In one embodiment, the particle size of the nano titanium dioxide is 20 to 50 nm.

[0011] In one embodiment, the defoaming agent is a polysiloxane defoaming agent.

[0012] In one embodiment, the raw materials include the following components, measured by mass: 35 parts of slag, 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of phenylethylamine and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a mass ratio of 1:5, and the modulus of the water glass is 1.1.

[0013] The present invention also provides a method for preparing the graphene oxide geopolymer coating, comprising the following steps: taking slag and fly ash according to a proportion, stirring and mixing, and obtaining dry material A; taking an activator and water according to a proportion, stirring and mixing, and obtaining solution B; taking graphene oxide and the solution B according to a proportion, mixing, and using ultrasonic dispersion to fully disperse the graphene oxide in the solution B, and obtaining solution C; taking a water reducer, a defoamer, an acrylic emulsion and phenylethylamine according to a proportion, adding them to the solution C, stirring and mixing, and obtaining solution D; stirring and mixing the dry material A and the solution D, and obtaining the graphene oxide geopolymer coating.

[0014] The present invention also provides the use of the above-mentioned graphene oxide geopolymer coating or the graphene oxide geopolymer coating prepared by the above-mentioned preparation method in steel corrosion protection.

[0015] The present invention also provides an anti-corrosion steel material, comprising a steel bar substrate and an anti-corrosion coating coated on the surface of the steel bar substrate, wherein the anti-corrosion coating is formed by the above-mentioned graphene oxide geopolymer coating or the graphene oxide geopolymer coating prepared by the above-mentioned preparation method.

[0016] The present invention also provides a method for preparing the above-mentioned anti-corrosion steel, comprising the following steps: coating the above-mentioned graphene oxide geopolymer coating on the surface of a steel bar substrate, and then placing it in a curing environment for curing for 7 days to obtain the anti-corrosion steel.

[0017] In one embodiment, the conditions of the curing environment are: temperature 25±0.5°C, relative humidity 95±5%.

[0018] The above solution of the present invention has the following beneficial effects:

[0019] The graphene oxide geopolymer coating of the present invention uses slag and fly ash as gel materials, and through the interaction between the two, a geopolymer with low porosity and high density is formed, the corrosion resistance and stability of the geopolymer are improved, and the geopolymer is modified by adding graphene oxide to slow down the shrinkage and cracking of the coating; further, by using an activator with a low water glass modulus (1.0-1.5) to adapt to the activation of slag and fly ash as gel materials, not only can the problems of alkali efflorescence and severe shrinkage of the geopolymer be avoided, but also the gelling material can be fully reacted to obtain a denser internal structure to improve its structural density. solidity (the denser, the more resistant to ion corrosion); at the same time, by adjusting the amount of activator added to about 19-25% of the weight of the gel material, a low-concentration alkaline solution can be formed, which can avoid subsequent alkali efflorescence on the one hand and reduce costs on the other hand; the amino group in phenylethylamine can not only react with the active functional groups in the geopolymer matrix to form covalent bonds, but also react with the carboxyl and epoxy groups on the surface of graphene oxide to form stable covalent bonds. Due to the addition of phenylethylamine, the cross-linking of the two becomes tighter, which can further improve the corrosion resistance and various performances and significantly extend the service life of the metal material.

[0020] Specifically, the present invention modifies geopolymer by adding nano-material graphene oxide. The geopolymer raw materials use slag and fly ash as gel materials. By adding graphene oxide, its internal structure can be improved, microcracks can be filled, and the interior can be more compact, and finally a geopolymer with low porosity and high density can be formed, which greatly improves the working performance and corrosion resistance of the geopolymer. In addition, graphene oxide will be reduced to reduced graphene oxide in an alkaline solution, which increases the interface interaction between graphene and geopolymer, helps to enhance the interface adhesion performance of the composite material, thereby improving its durability and stability; and because of the reduction reaction, the oxidized groups on the reduced graphene oxide are reduced, so that the graphene oxide changes from the wrinkled state to the flat state of the reduced graphene oxide, allowing Si-O tetrahedrons and Al-O tetrahedrons to aggregate on the surface of the reduced graphene oxide, and form a high polymerization degree, long-range ordered aluminum silicate structure through chemical bonding, and finally improve various performances such as mechanics.

[0021] In the present invention, an activator with a relatively low modulus (1.0-1.5) of water glass is used. Since the modulus of water glass is relatively low, it can be adapted to the activation of slag and fly ash as gel materials, which can not only further improve the problems of alkali blooming and severe shrinkage of geopolymers, but also enable the gelling material to fully react to obtain a denser internal structure to improve its corrosion resistance. At the same time, by adjusting the amount of the activator added to 19-25% of the weight of the gel material, a low-concentration alkaline solution can be formed, which can avoid subsequent alkali blooming on the one hand and reduce costs on the other.

[0022] In the above geopolymer raw materials, since water will participate in the hydration reaction, the amount of water added will affect the progress of the hydration reaction. When the amount of water added is too much or too little, the working performance of the coating will be poor. When the amount of water added is too much, the calcium silicate in the material will be diluted, causing it to lose a certain degree of cohesion and adhesion, thereby reducing the bonding performance. When the amount of water added is too little, the polymerization reaction will be too intense, and the coating will crack during the curing process. Therefore, the amount of water added in the preparation raw material is preferably 36% to 40% of the weight of the gel material. When the amount of water added is within this range, a geopolymer coating that meets the working performance can be prepared.

[0023] In the above formula, the water reducer can reduce the amount of water added and improve the fluidity of the geopolymer coating. The preferred water reducer is a polycarboxylic acid water reducer, which has the advantages of a small amount of addition and can significantly reduce the amount of water added. More importantly, the polycarboxylic acid water reducer can reduce the attraction between graphene oxide sheets through the action of its surfactant, so that the sheets are dispersed, thereby effectively improving the dispersion performance of graphene oxide in the solution.

[0024] In addition, because bubbles are generated in the above geopolymer raw materials during the reaction, if these bubbles are not eliminated in time, pores will be formed inside the geopolymer, and these pores will cause the density of the geopolymer coating to decrease, and ultimately limit its application. Therefore, the raw materials for preparing the above geopolymer also include a defoaming agent, which can quench the formed bubbles and avoid the formation of pores in the geopolymer, thereby further improving the density of the graphene oxide geopolymer coating.

[0025] Nano titanium dioxide is also added to the above formula. Because of its small particle size, the fine particles of nano titanium dioxide fill the internal pores and micro cracks of the geopolymer coating, further enhancing the density and hardness of the coating, while improving the adhesion between the geopolymer coating and the substrate, making the coating adhere more firmly to the surface of the substrate. In addition, the uniform dispersion of nano titanium dioxide can improve the uniformity of the coating, enhance the bonding performance of the coating, reduce weak areas, and reduce the shedding and peeling of the coating during use, thereby improving the overall wear resistance. Nano titanium dioxide increases the hardness and wear resistance of the coating, thereby extending the service life of the coating in an anti-corrosion environment, and finally achieving the effect of improving its protection of steel bars.

[0026] In the above formula, the hydrophobic properties of the geopolymer are enhanced by adding acrylic emulsion. Because acrylic groups can effectively repel water molecules, these hydrophobic groups will naturally form a hydrophobic layer on the surface of the material, reducing the surface energy of the geopolymer, making water droplets form a larger contact angle on its surface, thereby improving the hydrophobicity of the material and making the anti-corrosion performance of the geopolymer coating better.

[0027] In the above embodiment, by adding phenylethylamine, the amine group can not only react with the active functional groups in the geopolymer matrix to form a covalent bond, but also react with the carboxyl and epoxy groups on the surface of graphene oxide to form a stable covalent bond. Due to the addition of phenylethylamine, the crosslinking of the two becomes tighter, and the silicon-oxygen tetrahedron is formed on the surface of graphene oxide, so that the mesh structure of geopolymer and graphene oxide forms a stable composite structure with better stability, further improving the synergistic effect of geopolymer and graphene oxide, so that graphene oxide can form a stronger crosslinking structure with geopolymer, thereby further improving the anti-corrosion and various aspects of performance. At the same time, because of the generation of more stable covalent bonds, the adhesion of the coating is improved, thereby avoiding the peeling and falling off of the coating in seawater, thereby enhancing the working performance of the geopolymer anti-corrosion coating. Graphene oxide modified by phenylethylamine can form a dense anti-corrosion coating, effectively blocking the penetration of chloride ions in seawater, thereby reducing the corrosion rate of metal materials, and this shielding effect can significantly extend the service life of metal materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The actual pictures of the steel bars of Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention after being electrified for 24 hours for accelerated corrosion, from left to right are Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2;

[0029] Figure 2 The actual pictures of the steel bars of Examples 1 to 4 and Comparative Examples 1 to 2 of the present invention after being electrified for 72 hours for accelerated corrosion, from left to right are Example 1, Example 2, Example 3, Example 4, Comparative Example 1, and Comparative Example 2;

[0030] Figure 3 The polarization curve diagram is obtained by measuring the corrosion resistance of the steel bar samples of Examples 1 to 4 and Comparative Example 1 in a 3.5wt% NaCl solution using a dynamic potentiodynamic scanning polarization curve according to the present invention;

[0031] Figure 4 The following are actual pictures of steel bars with different coatings after 14 days of salt spray test, from left to right: Example 1, Control Example 1, epoxy resin coated steel bars, and commercially available metal anti-corrosion coated steel bars. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The reagents and instruments used in the examples are conventionally selected in the art unless otherwise specified. The experimental methods without specific conditions in the examples are implemented according to conventional conditions, such as the conditions described in the literature, books or methods recommended by the manufacturer.

[0034] Example 1

[0035] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide (particle size 20-50nm), 1 part of acrylic emulsion, 1 part of phenylethylamine, and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a mass ratio of 1:5, and the modulus of the water glass is 1.1.

[0036] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0037] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0038] Example 2 (the difference from Example 1 is that the modulus of the stimulator is larger)

[0039] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of phenylethylamine, and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a weight ratio of 1:5, and the modulus of the water glass is 1.5.

[0040] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0041] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0042] Example 3 (the difference from Example 1 is that the modulus of the exciter is smaller)

[0043] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of phenylethylamine, and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a weight ratio of 1:5, and the modulus of the water glass is 0.9.

[0044] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0045] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0046] Example 4 (the difference from Example 1 is that the amount of graphene oxide added is higher)

[0047] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of phenylethylamine, and 0.05 part of graphene oxide; the activator is composed of sodium hydroxide and water glass in a weight ratio of 1:5, and the modulus of the water glass is 1.1.

[0048] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0049] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0050] Comparative Example 1 (the difference from Example 1 is that graphene oxide is not added)

[0051] A geopolymer coating, wherein the raw materials for preparation include, by weight: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, and 1 part of phenylethylamine; the activator is composed of sodium hydroxide and water glass in a weight ratio of 1:5, and the modulus of the water glass is 1.1.

[0052] Slag and fly ash are taken according to the proportion, and stirred to mix well to obtain dry material A; activator and water are taken according to the proportion, and stirred to mix well to obtain solution B; water reducer, defoamer, acrylic emulsion and phenylethylamine are taken according to the proportion, added to solution B, and stirred to mix well to obtain solution D; dry material A and solution D are stirred to mix well to obtain geopolymer coating.

[0053] Use a brush to apply the geopolymer coating prepared in the above steps on the pre-treated steel substrate surface. After curing, transfer the coating to a 60°C oven for curing for 18 hours, take it out and place it in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain coated steel.

[0054] Comparative Example 2

[0055] This comparative example is ordinary steel without coating.

[0056] Comparative Example 3

[0057] The difference between this reference example and Example 1 is only that phenylethylamine is not added.

[0058] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 3 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a mass ratio of 1:5, and the modulus of the water glass is 1.1.

[0059] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0060] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0061] Comparative Example 4

[0062] The difference between this reference example and Example 1 is that phenylethylamine is replaced by acetophenone.

[0063] A graphene oxide geopolymer coating comprises raw materials, calculated by weight, including: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of acetophenone, and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a weight ratio of 1:5, and the modulus of the water glass is 1.1.

[0064] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0065] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0066] Comparative Example 5

[0067] The difference between the present embodiment and Example 1 is only that the addition of phenethylamine is 2 parts.

[0068] A graphene oxide geopolymer coating, the preparation raw materials of which include, by weight: 35 parts of slag (grade S95), 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 1 part of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 0.02 parts of graphene oxide and 2 parts of phenylethylamine; the activator is composed of sodium hydroxide and water glass in a mass ratio of 1:5, and the modulus of the water glass is 1.1.

[0069] Slag and fly ash are taken according to a proportion, and stirred and mixed to obtain dry material A; an activator and water are taken according to a proportion, and stirred and mixed to obtain solution B; graphene oxide is taken according to a proportion and mixed with solution B, and ultrasonic dispersion is used to fully disperse the graphene oxide in solution B to obtain solution C; a water reducer, a defoamer, an acrylic emulsion and phenylethylamine are taken according to a proportion, added to solution C, and stirred and mixed to obtain solution D; dry material A and solution D are stirred and mixed to obtain graphene oxide geopolymer coating.

[0070] Use a brush to apply the graphene oxide geopolymer coating prepared in the above steps on the pre-treated surface of the steel substrate. After curing, the coating is transferred to a 60°C oven for curing for 18 hours, then taken out and placed in a curing environment (temperature of 25±0.5°C, relative humidity of 95±5%) for 7 days to obtain anti-corrosion steel.

[0071] The steel prepared in the above-mentioned embodiment and control example was subjected to an electric accelerated corrosion test: the steel exposure section length was controlled to be 100 mm for the electric accelerated corrosion test, wherein the test voltage was 1.5 V, the power-on time was 72 hours, and the salt solution in the power-on device was a 3.5wt% sodium chloride solution. After the power-on was completed, the rust products and residual coating on the surface of the steel bar were removed, and the mass of the steel bar sample was weighed after pickling and drying, and the mass loss was calculated. The results are shown in Table 1.

[0072] Table 1 Steel bar mass loss rate

[0073]

[0074] like Figure 1 The following are the actual pictures of the steel bars of Examples 1 to 4 and Comparative Examples 1 to 2 after being electrified for 24 hours. Figure 2The picture shows the actual object of the above steel bars after being electrified for 72 hours, where the left 1 is the steel bar of Example 1, and the other steel bars are arranged in order from left to right. It can be seen that under the same corrosion conditions, the steel bars of Example 1 have the least corrosion products and the lowest mass loss after electrification for 72 hours, which is only 1% of the uncoated steel bars; and the corrosion development of Example 1 is slower than that of other steel bars. In Examples 2 and 3, due to the modulus of the alkali activator, the adhesion of the coating to the steel bars is reduced, and because the modulus of Example 2 is reduced, the coating has obvious shedding after electrification. Compared with Control Example 1, the steel bars with added graphene oxide have significantly improved anti-corrosion effect in terms of mass loss rate and external observation. In contrast, in Examples 3 to 5, where no phenylethylamine was added, there was a lack of effective articulation between the two, resulting in the inability of graphene oxide and the silicon-oxygen tetrahedron in the geopolymer to be well connected, leading to poor anticorrosion effects; and when too much phenylethylamine was added, the excessive phenylethylamine would react with the neutral components in the geopolymer, especially in a corrosive environment, resulting in a decrease in the chemical stability of the coating. In summary, the coating of Example 1 has a better protective effect.

[0075] Water contact angle (CA) is an indicator for evaluating the ability of a surface to contact water, and it is of great significance to anti-corrosion coatings. Surfaces with high water contact angles usually exhibit good hydrophobicity, that is, water droplets appear spherical on the surface and are not easy to adhere to and penetrate. As shown in Table 2, various wettabilities of water on the samples were obtained. In Example 1, water appeared spherical on the coating, and the CA of the water droplets was 118±0.4°. The coatings after adding acrylic emulsion and graphene oxide all showed hydrophobicity. The reason may be that acrylic acid in the form of emulsion can make the coating process more uniform and stable, ensuring that graphene oxide is evenly distributed on the surface of the geopolymer, thereby enhancing its hydrophobic properties. In contrast, the CA of water in the coating without the addition of graphene oxide is 81±0.5°. Therefore, the addition of an appropriate amount of graphene oxide helps to improve the hydrophobicity of the coating.

[0076] Table 2 Water contact angle of coating

[0077] Group Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Water contact angle / ° 118° 98 91 107° 81°

[0078] The corrosion resistance of steel bar samples in 3.5wt% NaCl solution was measured by potentiodynamic scanning polarization curve. The obtained polarization curve is shown in Figure 3 The polarization curve represents the relationship between the electrode potential and the polarization current or polarization current density. The corrosion potential is calculated by the Tafel curve extrapolation method, and the results are shown in Table 3 below.

[0079] Table 3 Corrosion current density

[0080]

[0081] Figure 3 The polarization curves of each group of steel bar samples are shown. It can be seen from the figure that the potential corresponding to the minimum current of each group of specimens has a tendency to move negatively. In the polarization curves of Example 1 and Example 4, there is an obvious passivation zone, which shows that the addition of graphene oxide can effectively generate an adsorption layer or oxide film in the coating, separate the steel bar and the solution, and reduce the corrosion rate of the metal. The corrosion potential is calculated by the Tafel curve extrapolation method. The corrosion current density in Example 1 is the lowest, which is only 0.01% of that in Control Example 1. It can be seen that the addition of a certain amount of graphene oxide has a qualitative improvement in the corrosion resistance of the coating.

[0082] Figure 4 The actual picture of steel bars with different coatings after 14 days of salt spray test, from left to right are Example 1, Control Example 1, epoxy resin coated steel bars, and commercially available metal anti-corrosion coated steel bars. The salt spray test results show that under the same test environment, the steel bar surface of Control Example 1 is severely corroded, and the exposed test surface of the steel bar is covered with reddish-brown rust products; the commercially available water-based metal anti-rust paint coated steel bars are also corroded, and a large amount of shedding and rust on the coating surface indicate that the coating has deteriorated; while for epoxy coated steel bars, it can be clearly observed that serious corrosion has occurred inside the steel bars; in contrast, the coated steel bars of Example 1 are also corroded under the test environment, but the degree of corrosion is relatively light, and fewer rust products are generated on the surface, and most of the unaffected areas are still maintained, indicating that the coating of Example 1 has the best protective effect on steel bars.

[0083] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A graphene oxide geopolymer coating, characterized in that: The raw materials include the following components in parts by mass: 35-40 parts of slag, 20-25 parts of fly ash, 20-25 parts of water, 10-15 parts of activator, 0.9-1.2 parts of water reducer, 1.5-2.7 parts of defoamer, 0.02-0.04 parts of graphene oxide, 1-2 parts of acrylic emulsion, 1-2 parts of nano titanium dioxide and 0.8-1.2 parts of phenylethylamine; wherein the activator is composed of sodium hydroxide and water glass, the modulus of the water glass is 1-1.5; the mass ratio of the sodium hydroxide to the water glass is 1:4-6; the particle size of the nano titanium dioxide is 20-50nm.

2. The graphene oxide geopolymer coating according to claim 1, characterized in that: The water reducing agent is a polycarboxylic acid water reducing agent.

3. The graphene oxide geopolymer coating according to claim 1, characterized in that: The defoamer is a polysiloxane defoamer.

4. The graphene oxide geopolymer coating according to claim 1, characterized in that: The raw materials include the following components in parts by mass: 35 parts of slag, 23 parts of fly ash, 1.2 parts of polycarboxylic acid water reducer, 23 parts of water, 2.7 parts of polysiloxane defoamer, 12 parts of activator, 1 part of nano titanium dioxide, 1 part of acrylic emulsion, 1 part of phenylethylamine and 0.02 parts of graphene oxide; the activator is composed of sodium hydroxide and water glass in a mass ratio of 1:5, and the modulus of the water glass is 1.

1.

5. A method for preparing the graphene oxide geopolymer coating according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: taking slag and fly ash according to a proportion, stirring and mixing, and obtaining dry material A; taking an activator and water according to a proportion, stirring and mixing, and obtaining solution B; taking graphene oxide according to a proportion, mixing, and using ultrasonic dispersion to fully disperse the graphene oxide in the solution B, and obtaining solution C; taking a water reducer, a defoamer, an acrylic emulsion and phenylethylamine according to a proportion, adding them to the solution C, stirring and mixing, and obtaining solution D; stirring and mixing the dry material A and the solution D, and obtaining the graphene oxide geopolymer coating.

6. Use of the graphene oxide geopolymer coating according to any one of claims 1 to 4 or the graphene oxide geopolymer coating prepared by the preparation method according to claim 5 in steel corrosion protection. 7.An anti-corrosion steel material, characterized in that: It comprises a steel bar substrate and an anti-corrosion coating coated on the surface of the steel bar substrate, wherein the anti-corrosion coating is formed by the graphene oxide geopolymer coating according to any one of claims 1 to 4 or the graphene oxide geopolymer coating prepared by the preparation method according to claim 5.

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