Geopolymer rust remover and its rust removal method

Abstract

This invention discloses a geopolymer rust remover and its rust removal method, relating to the field of metal rust removal technology. The proposed geopolymer rust remover comprises an alkaline activator and granulated blast furnace slag, wherein the granulated blast furnace slag is alkaline slag. This method utilizes a geopolymer rust remover slurry prepared from an alkaline activator and granulated blast furnace slag, which exhibits extremely low yield stress in a plastic state, easily penetrating deep into the rust cracks on the surface of rust-bearing metal. As the geopolymer reaction proceeds, the generated hydraulic geopolymer gradually covers the metal surface. The highly alkaline internal environment promotes the formation of soluble ferrates from rust, while the oxygen-deficient environment reduces the rust products to magnetite. The gel generated by the geopolymer reaction forms a mechanically interlocked structure with the reduced magnetite product. During the drying process, the gel generates shrinkage stress, and the hardened geopolymer shell naturally cracks and easily peels off, thereby achieving the transformation and removal of rust-bearing metal.

Description

Technical Field

[0001] This invention relates to the field of metal rust removal technology, and in particular to a geopolymer rust remover and its rust removal method. Background Technology

[0002] Large metal engineering structures, such as port quay cranes, yard cranes, cross-sea bridges, and offshore platforms, operate in harsh environments with high humidity and high salt spray for extended periods, making them highly susceptible to severe electrochemical corrosion. The rust formed by corrosion is typically loose and porous, possessing low strength and significant hygroscopicity. It continuously absorbs moisture and corrosive media such as chloride ions from the environment, forming a "corrosion cell" that further accelerates the corrosion process of the base metal, seriously threatening the structure's safety and service life.

[0003] Thorough surface pretreatment is crucial when performing corrosion protection on these large structures. Efficient rust removal not only removes harmful rust products but also exposes the true surface condition of the metal substrate, such as tiny pits and cracks, resulting in a clean metal surface with high surface energy and activity. This is a prerequisite for the subsequent organic anti-corrosion coating to adhere firmly and exert excellent protective performance.

[0004] However, existing rust removal technologies (such as ultra-high pressure water rust removal, sandblasting, laser rust removal, and mechanical power rust removal) still have many limitations in practical applications. Therefore, developing a green, efficient, and fast surface treatment technology that can effectively ensure the adhesion and protective performance of subsequent anti-corrosion coatings has become an urgent technical challenge to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to propose a geopolymer rust remover and its rust removal method, which aims to achieve in-situ rust removal of rusted metal surfaces in a green, efficient and fast manner, so as to ensure the adhesion and protective performance of subsequent anti-corrosion coatings.

[0006] To achieve the above objectives, the present invention proposes a geopolymer rust remover, comprising an alkaline activator and granulated blast furnace slag, wherein the granulated blast furnace slag is an alkaline slag.

[0007] Preferably, the chemical composition of the granulated blast furnace slag includes MgO, CaO, SiO2 and Al2O3, and the ratio of the total content of MgO and CaO to the total content of SiO2 and Al2O3 by mass is 1.0 to 1.1.

[0008] Preferably, the concentration of alkali metal cations in the alkali activator is 2-4 mol / kg, and the alkali metal cations are sodium ions or potassium ions.

[0009] Preferably, the mass ratio of the alkali activator to the granulated blast furnace slag is 1:(2-3).

[0010] Preferably, the alkaline activator is either an aqueous solution of sodium silicate or an aqueous solution of potassium silicate, and the modulus of the alkaline activator is 1.0 to 2.0.

[0011] Preferably, the particle size of the granulated blast furnace slag is 1–20 μm.

[0012] A rust removal method using the above-mentioned geopolymer rust remover includes the following steps: After mixing the alkaline activator and the granulated blast furnace slag, a geopolymer rust remover is obtained; The geopolymer rust remover is applied to the surface of the rusted metal to obtain a geopolymer coating; The polymer film is then applied to the surface of the geopolymer coating and cured. After the geopolymer coating hardens, the polymer film is removed and the system is left to cure naturally. After the geopolymer coating dries and cracks, the geopolymer coating is removed.

[0013] Preferably, the thickness of the geopolymer coating is 0.5 to 1.5 mm.

[0014] Preferably, the polymer film is made of any one of polyethylene, polyvinyl chloride, and polypropylene; the curing time for the film covering is 12 to 18 hours.

[0015] Preferably, the natural curing time is 24 to 48 hours, and the relative humidity is ≤80%.

[0016] The technical solution of this invention utilizes a geopolymer rust remover slurry prepared from an alkali activator and granulated blast furnace slag. This slurry exhibits extremely low yield stress in a plastic state, allowing it to easily penetrate deep into the rust cracks on the surface of rust-bearing metal. As the geopolymer reaction proceeds, the generated hydraulic geopolymer gradually covers the metal surface. The highly alkaline internal environment promotes the formation of soluble ferrates from the rust, while the oxygen-deficient environment reduces the rust products to magnetite. The gel generated by the geopolymer reaction forms a mechanically interlocked structure with the reduced magnetite product. During the drying process, the gel generates shrinkage stress, and the hardened geopolymer shell naturally cracks and easily peels off, thereby achieving the transformation and removal of rust-bearing metal. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1This is a surface condition diagram of the rusted steel plate in Embodiment 1 of the present invention; Figure 2 This is a surface state diagram of the geopolymer coating drying and cracking in Embodiment 1 of the present invention; Figure 3 This is a surface state diagram of the rust-removed metal in Embodiment 1 of the present invention.

[0019] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.

[0022] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the use of "and / or" or "and / or" throughout the text includes three parallel solutions. For example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0023] Unless otherwise specified, the raw materials, reagents and equipment used in this invention are all conventional commercially available reagents and equipment.

[0024] Currently, existing rust removal technologies (such as ultra-high pressure water rust removal, sandblasting and shot blasting, laser rust removal, and mechanical power rust removal) still have many limitations in practical applications. Specifically: Ultra-high pressure water rust removal uses a booster pump to pressurize water to over 2500-3000 atmospheres, forming a high-speed jet through a special nozzle. This jet impacts and peels off rust, old paint, and salt deposits. It boasts advantages such as high efficiency, dust-free operation, and wide applicability. However, the equipment is expensive, and rapid drying is required after treatment to prevent flash rusting. Sandblasting and shot blasting use compressed air to propel abrasives (such as silica sand or steel shot) to impact the metal surface for rust removal. This can meet the requirements for high-adhesion coatings at Sa2.5 grade (thorough rust removal, leaving only slight discoloration). However, it causes severe dust pollution, requires a sealed enclosure, and has low abrasive recovery rates and high costs. Laser rust removal uses the photothermal effect of a high-energy laser beam to evaporate the rust layer, achieving non-contact rust removal. It can remove rust layer by layer without damaging the substrate, requiring no abrasives or chemical agents. However, the rust layer needs to be treated multiple times, resulting in low efficiency. Furthermore, laser equipment is expensive and has low adoption rates. Mechanical power rust removal methods include using traditional tools such as angle grinders and wire brushes for rust removal. These methods are often used for auxiliary repairs or small-area operations. However, they are inefficient and labor-intensive when performing rust removal on large metal engineering structures.

[0025] In order to achieve in-situ rust removal on rusty metal surfaces, this technical solution proposes a geopolymer rust remover, which includes an alkaline activator and granulated blast furnace slag, wherein the granulated blast furnace slag is an alkaline slag.

[0026] The geopolymer rust remover in this solution is prepared from an alkaline activator and granulated blast furnace slag. The resulting rust remover slurry, after mixing, exhibits extremely low yield stress in a plastic state, allowing it to easily penetrate deep into the rust cracks on the surface of rust-bearing metal. As the geopolymer reaction proceeds, the generated hydraulic geopolymer gradually covers the metal surface. The highly alkaline internal environment promotes the formation of soluble ferrates from the rust, while the oxygen-deficient environment reduces the rust products to magnetite. The gel generated by the geopolymer reaction forms a mechanically interlocked structure with the reduced magnetite product. During the drying process, the gel generates shrinkage stress, and the hardened geopolymer shell naturally cracks and easily peels off, thus achieving the transformation and removal of rust-bearing metal.

[0027] Furthermore, one of the raw materials for the geopolymer reaction in this scheme is granulated blast furnace slag, which is a molten material mainly composed of aluminosilicates formed during blast furnace ironmaking. This slag is quenched in water to form granules, which are then further ground into powder. Based on the ratio of alkaline oxides (such as MgO and CaO) to acidic oxides (such as SiO2 and Al2O3) in the chemical composition of granulated blast furnace slag, it can generally be classified into alkaline slag, acidic slag, and neutral slag. This scheme specifically selects alkaline granulated blast furnace slag as the raw material for the rust remover. On the one hand, its extremely low yield stress in its slurry state allows for the penetration of nanoscale pores, which is more conducive to the rust remover slurry penetrating into the micro-cracks of the rust layer. On the other hand, its ability to produce significant drying shrinkage after solidification facilitates the rapid and effective peeling off of the hardened geopolymer shell, especially in thin layers, greatly improving the convenience of rust layer removal.

[0028] Furthermore, thanks to the aforementioned rust removal mechanism, the rust remover proposed in this solution, compared to existing rust removal technologies, can achieve the transformation and large-area removal of rust layers on metal surfaces without complex steps. The hardened geopolymer shell formed after rust layer transformation is easily peeled off, greatly improving rust removal efficiency and convenience. Simultaneously, the rust-removed metal surface can achieve or approach the performance of the coating after the same anti-corrosion treatment on the initial surface, ensuring the adhesion and protective performance of the anti-corrosion coating. Finally, the geopolymer rust remover in this solution uses low-cost raw materials, promotes solid waste resource utilization, and significantly reduces energy consumption and carbon emissions, which is of great significance for the corrosion protection of large-scale engineering structures.

[0029] To further explain, the chemical composition of the granulated blast furnace slag includes MgO, CaO, SiO2 and Al2O3, and the ratio of the total content of MgO and CaO to the total content of SiO2 and Al2O3 by mass is 1.0 to 1.1.

[0030] In a preferred embodiment of this technical solution, the alkalinity of the granulated blast furnace slag is further controlled to provide a high-alkaline environment for the rust remover slurry to promote the formation of soluble ferrates from rust. At the same time, a hardened layer can be formed rapidly in the early stage to ensure the oxygen-deficient environment required for the reduction reaction of rust products, thereby achieving effective rust transformation.

[0031] To further clarify, the concentration of alkali metal cations in the alkali activator is 2-4 mol / kg, and the alkali metal cations are sodium ions or potassium ions.

[0032] In another preferred embodiment of this technical solution, the concentration of alkali metal cations in the alkali activator is further controlled. It should be noted that the concentration of alkali metal cations in this solution is higher than that required for conventional applications of geopolymers (i.e., building materials). This means that the geopolymer slurry in this solution can have higher alkalinity and stronger drying shrinkage after curing, which is not only beneficial for rust removal but also for the rapid peeling of rust layers.

[0033] To further clarify, the mass ratio of the alkali activator to the granulated blast furnace slag is 1:(2-3).

[0034] This scheme also optimizes the mass ratio of alkali activator and granulated blast furnace slag. This ensures both good slurry fluidity and rapid development of the geopolymer strength. If the activator ratio is too low, the early yield stress will not be low enough, making it difficult for the slurry to penetrate the micro-cracks where rust products reside. The rust products may continue to react inside the rust remover, causing cracking. If the activator ratio is too high, the yield stress will be too low, making it difficult to form a homogeneous slurry. The liquid and slag particles will easily separate, leading to uneven reaction and difficulty in forming a complete sealed environment on the rusted metal surface.

[0035] Furthermore, the alkaline activator is either an aqueous solution of sodium silicate or an aqueous solution of potassium silicate, and the modulus of the alkaline activator is 1.0 to 2.0.

[0036] To further clarify, the particle size of the granulated blast furnace slag is 1–20 μm.

[0037] Furthermore, this solution also proposes a rust removal method using the aforementioned geopolymer rust remover, comprising the following steps: After mixing the alkaline activator and the granulated blast furnace slag, a geopolymer rust remover is obtained; The geopolymer rust remover is applied to the surface of the rusted metal to obtain a geopolymer coating; The polymer film is then applied to the surface of the geopolymer coating and cured. After the geopolymer coating hardens, the polymer film is removed and the system is left to cure naturally. After the geopolymer coating dries and cracks, the geopolymer coating is removed.

[0038] The rust removal method provided in this solution can achieve in-situ transformation of rust layers on rusty metal surfaces and removal of large-area loose corrosion products. Furthermore, the dried and cracked geopolymer coating (i.e., the hardened geopolymer shell) is easy to peel off, greatly improving rust removal efficiency and convenience. Simultaneously, the rust-removed metal surface can achieve or approach the performance of the coating after the same anti-corrosion treatment on the initial surface, ensuring the adhesion and protective performance of the anti-corrosion coating. Finally, apart from the raw materials used in the geopolymer rust remover in this solution, the additional raw materials and process costs used in the rust removal method are also low, significantly reducing the corrosion protection costs for large engineering structures.

[0039] In one specific embodiment, the geopolymer rust remover is applied by spraying. The alkaline activator and granulated blast furnace slag are mixed in proportion at the nozzle and then quickly sprayed onto the surface of the rusted metal to ensure the rust removal effect of the rust remover.

[0040] To further clarify, the thickness of the geopolymer coating is 0.5 to 1.5 mm.

[0041] In a preferred embodiment of this technical solution, the application thickness of the geopolymer coating is also controlled. If the thickness is too thin, oxygen can easily penetrate from the pores of the hardened material, which is not conducive to creating an internal anaerobic environment; if the thickness is too thick, although the hardened geopolymer coating will also crack, it will not be easy to remove the hardened material from the surface.

[0042] To further clarify, the polymer film is made of any one of polyethylene, polyvinyl chloride, and polypropylene; the curing time for the film covering is 12 to 18 hours.

[0043] To further clarify, the natural curing time is 24–48 hours, and the relative humidity is ≤80%.

[0044] The present invention will be further illustrated below through specific embodiments: Example 1 1. Prepare the stainless steel plate: The standard sandblasted steel plate was subjected to a 240-hour neutral salt spray test according to GB / T 1771-2007. After removal, it was rinsed with 50℃ hot water while brushing with a nylon brush for 3 minutes, then rinsed with tap water while brushing with a nylon brush for 5 minutes. Next, it was dried at (105±2)℃ for 1 hour. The surface rust was then manually removed with a wire brush, leaving firmly adhered rust. The surface dust was blown away with high-pressure air, resulting in a rusted steel plate. The surface condition is shown in the image below. Figure 1 As shown.

[0045] II. Rust Removal: Alkali activator and granulated blast furnace slag are mixed at the nozzle at a mass ratio of 33:67 to obtain a geopolymer rust remover; The geopolymer rust remover is sprayed onto the surface of rusted metal to obtain a geopolymer coating with a thickness of 1 to 1.5 mm; The polymer film is covered on the surface of the geopolymer coating and cured for 12 hours. After removing the polymer film, it is then left to cure naturally, that is, cured in a natural environment with relative humidity ≤80% for 24 hours. The geopolymer coating dried and cracked, and its surface condition is shown in the figure below. Figure 2 As shown, from Figure 2 As can be seen from the surface state diagram, green appears locally on the coating surface. The reason for this appearance is that one of the reaction products is Mg-Al LDH (magnesium-aluminum layered bimetallic hydroxide) with polysulfide ions as interlayer anions. Since polysulfide ions can only be formed in an oxygen-deficient environment, it fully proves that the geopolymer rust remover of this solution can provide a sufficient oxygen-deficient environment. The rust-removed metal is obtained by hammering and scraping off the polymer coating. The surface condition of the rust-removed surface is shown in the image below. Figure 3 As shown.

[0046] Raw material description: The alkaline activator is an aqueous solution of potassium silicate with a modulus of 1.0, a solid content of 41 wt%, and a potassium ion concentration of 3 mol / kg. The average particle size of the granulated blast furnace slag is 6 μm, and its chemical composition includes 9.6 wt% MgO, 37.6 wt% CaO, 34.1 wt% SiO2 and 12.3 wt% Al2O3. The polymer film is made of polyethylene.

[0047] III. Protection Verification: According to the conventional formula, epoxy resin (E-44) is dissolved in xylene and n-butanol, then curing agent is added, and after manual mixing, it is allowed to stand for 10 minutes to defoam, thus obtaining epoxy varnish. The epoxy varnish was uniformly coated onto the rust-removed surface of the rusted metal, then cured in an oven at 40°C for 4 hours, followed by curing at 60°C for 20 hours, and finally dried at room temperature for 7 days. The surface drying time and complete drying time of the coating were recorded simultaneously during the curing process to obtain the epoxy varnish coating. The appearance of the epoxy varnish coating was observed, and its thickness and adhesion were tested and recorded. The rust-removed metal coated with epoxy varnish was immersed in a 3.5% NaCl solution for electrochemical impedance spectroscopy, and the low-frequency impedance modulus was recorded after 10 days of immersion.

[0048] After sealing the rust-removed metal edges with an epoxy varnish coating, the metal was placed in a salt spray chamber for a neutral salt spray test, and the coating protection time was recorded. The results are shown in Table 1 below.

[0049] Example 2 1. Prepare the rusted steel plate: Same as in Example 1.

[0050] II. Rust Removal: Alkali activator and granulated blast furnace slag are mixed at the nozzle at a mass ratio of 30:70 to obtain a geopolymer rust remover; The geopolymer rust remover is sprayed onto the surface of rusted metal to obtain a geopolymer coating with a thickness of 1 to 1.5 mm; The polymer film was applied to the surface of the geopolymer coating and cured for 18 hours. After removing the polymer film, the curing process was carried out naturally, i.e., cured for 48 hours in a natural environment with a relative humidity of ≤80%. The geopolymer coating dries and cracks; slight vibration causes the geopolymer coating to peel off and be scraped off, yielding rust-free metal.

[0051] Raw material description: The alkaline activator is an aqueous solution of sodium silicate with a modulus of 2.0, a solid content of 40 wt%, and a sodium ion concentration of 2 mol / kg. The average particle size of the granulated blast furnace slag is 6 μm, and its chemical composition includes 9.6 wt% MgO, 37.6 wt% CaO, 34.1 wt% SiO2 and 12.3 wt% Al2O3. The polymer membrane is made of polypropylene.

[0052] III. Protection Verification: Same as Example 1.

[0053] Comparison Example 1. Prepare standard sandblasted steel plates; II. Protection Verification: Protection verification was performed on the surface of a standard sandblasted steel plate. The remaining steps were the same as in Example 1.

[0054] Comparative Example 1 1. Prepare the rusted steel plate: Same as in Example 1.

[0055] II. Protection Verification: Protection verification was performed on the rusted surface of the rusted steel plate. The remaining steps were the same as in Example 1.

[0056] Comparative Example 2 1. Prepare the rusted steel plate: Same as in Example 1.

[0057] II. Rust Removal: Use tools such as steel wool and sandpaper to polish and remove rust from the rusted surface of the steel plate.

[0058] III. Protection Verification: Same as Example 1.

[0059] Comparative Example 3 1. Prepare the rusted steel plate: Same as in Example 1.

[0060] II. Rust Removal: Ultra-high pressure water guns are used to impact and remove rust from the rusted surface of the steel plate.

[0061] III. Protection Verification: Same as Example 1.

[0062] Table 1

[0063] Table 1 shows the performance test results of epoxy clear coats under different treatment methods, clearly demonstrating the key impact of the rust removal process on the protective effect of the coating. Specifically: First, regarding the appearance and thickness of the coating, Examples 1, 2, the Control Example, and Comparative Examples 2 and 3 all exhibited smooth and even surfaces with a stable thickness of 180–220 μm. This indicates that epoxy varnish can form a continuous and uniform film on a clean or effectively derusted substrate. However, Comparative Example 1, applied directly to the rusted surface of a rusted steel plate without any derusting treatment, resulted in an uneven coating appearance and extremely uneven thickness (70–350 μm). This is because the rust layer is porous and expanded, leading to uneven paint penetration and noticeable undulations after drying.

[0064] Regarding adhesion, Examples 1 (4.6 MPa) and 2 (3.2 MPa) were both superior to the control example (3.8 MPa), indicating that using the geopolymer rust remover of this application to remove rust from the surface of rusted steel plates can enhance the adhesion between the coating and the rust-removed substrate to a certain extent. Comparative Example 1 showed the lowest adhesion, confirming that the rust layer is a weak adhesion layer. While Comparative Example 2 (mechanical grinding, 3.6 MPa) and Comparative Example 3 (high-pressure water washing, 4.0 MPa) showed some improvement, Example 1 exhibited the most outstanding adhesion, demonstrating the superior advantage of chemical rust removal at the microscopic interface.

[0065] Electrochemical impedance spectroscopy is a key indicator for evaluating the corrosion resistance of coatings. Both the control example and Comparative Example 2 achieved a value of 10. 9 Ω·cm 2 This demonstrates that the coating exhibits excellent barrier performance on rust-free or mechanically polished surfaces. Example 1 (9.6 × 10⁻⁶) 8 Example 1 and Example 2 (8.8 × 10) 8 Although slightly lower than the control group, it still remained at 10. 8 ~10 9 The magnitude indicates that the rust conversion products after chemical rust removal did not significantly weaken the barrier properties of the coating. In contrast, Comparative Example 1 showed only 10... 6 Ω·cm 2 The corrosion rate decreased by three orders of magnitude, and the residual conductive ions and pores in the rust layer provided a rapid penetration channel for the corrosive medium. Comparative Example 3 (9.0 × 10⁻⁶) 8 It also performs well; high-pressure water washing can effectively remove loose rust layers.

[0066] The protection time of the neutral salt spray test further verified the above pattern. Examples 1 and 2, control examples, and comparative examples 2 and 3 could all withstand 480 hours and achieve the same level of protection.

[0067] In summary, Table 1 clearly demonstrates that if epoxy varnish is applied directly to rust-bearing steel plates without rust removal (Comparative Example 1), the coating appearance, adhesion, impedance, and salt spray resistance are severely degraded. However, rust removal treatment using the geopolymer rust removers of Examples 1 and 2 not only yields a smooth and even coating with high adhesion and electrochemical impedance comparable to the control example, but also achieves the required protection time, demonstrating excellent overall performance. This is a highly efficient and feasible pretreatment solution for rust-bearing steel plates before coating. While mechanical grinding and high-pressure water washing are also effective, the former is inefficient and labor-intensive, and the latter has poor adaptability to complex surfaces. The geopolymer rust remover and its rust removal method provided in this solution have greater engineering application value in terms of ease of operation and enhanced interfacial bonding.

[0068] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A geopolymer rust remover, characterized in that, It includes an alkali activator and granulated blast furnace slag, wherein the granulated blast furnace slag is an alkaline slag.

2. The geopolymer rust remover as described in claim 1, characterized in that, The granulated blast furnace slag has the following chemical composition: MgO, CaO, SiO2 and Al2O3, and the ratio of the total content of MgO and CaO to the total content of SiO2 and Al2O3 by mass is 1.0 to 1.

1.

3. The geopolymer rust remover as described in claim 1, characterized in that, The concentration of alkali metal cations in the alkali activator is 2-4 mol / kg, and the alkali metal cations are sodium ions or potassium ions.

4. The geopolymer rust remover as described in claim 1, characterized in that, The mass ratio of the alkali activator to the granulated blast furnace slag is 1:(2-3).

5. The geopolymer rust remover as described in claim 1, characterized in that, The alkaline activator is either an aqueous solution of sodium silicate or an aqueous solution of potassium silicate, and the modulus of the alkaline activator is 1.0 to 2.

0.

6. The geopolymer rust remover as described in claim 1, characterized in that, The particle size of the granulated blast furnace slag is 1–20 μm.

7. A rust removal method, characterized in that, Using the geopolymer rust remover according to any one of claims 1 to 6 includes the following steps: After mixing the alkaline activator and the granulated blast furnace slag, a geopolymer rust remover is obtained; The geopolymer rust remover is applied to the surface of the rusted metal to obtain a geopolymer coating; The polymer film is covered over the surface of the geopolymer coating and then cured. After the geopolymer coating hardens, the polymer film is removed and the process is left to natural curing. After the geopolymer coating dries and cracks, the geopolymer coating is removed.

8. The rust removal method as described in claim 7, characterized in that, The thickness of the geopolymer coating is 0.5 to 1.5 mm.

9. The rust removal method as described in claim 7, characterized in that, The polymer film is made of any one of polyethylene, polyvinyl chloride, and polypropylene; The curing time for the film covering is 12 to 18 hours.

10. The rust removal method as described in claim 7, characterized in that, The natural curing time is 24-48 hours, and the relative humidity is ≤80%.

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