Preparation method and application of a corrosion inhibitor for deep coal mine anchor cable grouting

Abstract

The invention discloses a preparation method and application of a corrosion inhibitor for deep coal mine anchor cable grouting. A corrosion inhibitor for deep coal mine anchor cable grouting is composed of Cr2O3 and Na3PO4; the corrosion inhibitor for grouting is prepared by the following steps: adding Cr2O3 and Na3PO4 into an air flow pulverizer, pulverizing to D50≤15μm, with the mixing degree CV value <5%, and the pressure of the air flow pulverizer being 0.8 MPa. The invention effectively fills a part of the blank of corrosion inhibitors for deep well coal mines, enriches the types of existing products, and provides more choices for the protection work in deep coal mine mining. This corrosion inhibitor can effectively inhibit the corrosion rate of the anchor cable grouting anchoring material in harsh environments such as high humidity, high salinity, and complex stress in deep coal mines, greatly extending the service life of the anchoring material and ensuring the stability and safety of the anchor cable structure during the deep coal mine mining process.

Description

Technical Field

[0001] The present invention belongs to the field of anti-corrosion of deep coal mine support materials, and particularly relates to a preparation method and application of a corrosion inhibitor for grouting of anchor cables in deep coal mines. Background Art

[0002] The engineering geological environment of deep coal mines presents typical characteristics of the combined action of "high ground stress - high osmotic pressure - high temperature" and strong mining disturbance (i.e., "three highs and one disturbance"). The large deformation control of roadway surrounding rock highly depends on the prestressed anchor cable support system. In the operation of deep coal mine exploitation, its complex and harsh geological conditions and operation environment pose extremely high requirements on the anchor cable anchoring system. However, the special deep geological mechanics environment poses a severe threat of electrochemical corrosion to the service of anchor cables. Once the anchor cables are corroded, their mechanical properties will significantly decline, which may lead to anchoring failure and then trigger serious safety accidents such as roadway collapse, threatening not only the lives of operating personnel but also causing huge economic losses. At the same time, frequently replacing the corroded and damaged anchor cables will greatly increase the mining cost and maintenance workload, seriously affecting the efficiency and economic benefits of coal mine exploitation. Therefore, the anti-corrosion of anchor cable anchoring is crucial for the safe production and efficient operation of deep coal mines.

[0003] Engineering practice shows that in the support structure using silicate-based grouting anchoring, due to the difference in the structural synergy of the material systems (carbon steel anchor cable body and silicate grouting body) between the free section and the anchoring section of the anchor cable, a local micro-cell effect is formed under the action of the seepage of surrounding rock fissure water, and its potential difference can reach 200 - 500 mV, constituting a typical galvanic corrosion micro-environment system. Chloride ion erosion, as the dominant corrosion inducing factor, has multi-scale characteristics in its action mechanism: at the microscopic level, the alkaline solution (pH≈12) in the porous structure (porosity 15 - 25%) of the silicate grouting body can generate a dense Fe3O4 / γ-Fe2O3 passivation film on the surface of the anchor cable, but Cl - destroys the self-healing process of the passivation film through the adsorption competition mechanism; at the mesoscopic level, the insufficient anti-seepage property of the grouting body (permeability coefficient > 1×10 -7 cm / s) leads to the formation of a dominant seepage channel for the surrounding rock fissure water (Cl - concentration is often > 500 mg / L) under the drive of capillary action and osmotic pressure; at the macroscopic level, the release of tectonic stress in the surrounding rock causes 0.1 - 0.5 mm-level dynamic cracks to occur at the interface between the grouting body and the surrounding rock, inducing the direct exposure of the anchor cable matrix to a high-Cl - corrosion medium environment.

[0004] The current protection technologies have significant limitations: the hot-dip galvanized coating is prone to intergranular peeling under the action of shear displacement of the surrounding rock; the organic anti-corrosion coating ages and fails under the influence of high geothermal temperature (>45°C) and mechanical damage; the PE sheath is damaged due to stress concentration caused by large deformation of the surrounding rock. In contrast, the chemical inhibitor technology currently has broad development prospects and has the advantages of being non-toxic, environmentally friendly, not affected by the metal structure, and having a stable effect. Selecting a suitable inhibitor can effectively slow down the corrosion rate and maintain the stability of deep coal mine roadways. The chemical inhibitor technology realizes multi-mechanism collaborative protection through molecular design: anodic inhibitors (such as nitrites) improve the self-healing ability of the passive film by promoting the formation of the stable phase of γ-FeOOH; cathodic inhibitors (such as molybdates) inhibit the electron mobility of the oxygen reduction reaction; organic amine mixed inhibitors reduce the density of active sites on the metal surface through the adsorption film formation mechanism (following the Langmuir adsorption model). Experiments show that the grouting body doped with 2.5% composite inhibitor can reduce the corrosion rate of Q235 steel from 0.25 mm / a to 0.03 mm / a, and at the same time form a synergistic anti-seepage system with the nano-SiO2 modified grouting body (the permeability coefficient is reduced to 5×10 -9 cm / s), significantly improving the reliability of the whole life cycle of the deep roadway support structure. Therefore, developing an anchor cable grouting inhibitor suitable for the deep coal mine environment has become one of the important research directions of current coal mine support technologies. Summary of the Invention

[0005] One of the purposes of this application is to provide a deep coal mine anchor cable grouting inhibitor incorporated into the anchoring material, which is suitable for the deep coal mine anchor cable grouting anchoring material and will not cause adverse effects.

[0006] To achieve the above purpose, this application provides the following technical solutions:

[0007] A deep coal mine anchor cable grouting inhibitor, the grouting inhibitor is composed of Cr2O3 and Na3PO4;

[0008] The grouting inhibitor is prepared by the following steps:

[0009] Add Cr2O3 and Na3PO4 into an air-flow pulverizer, pulverize until D50≤15μm, and the mixing degree CV value <5%. The pressure of the air-flow pulverizer is 0.8 MPa.

[0010] Preferably, the mass ratio of Cr2O3 to Na3PO4 is 1-5:1.

[0011] Another purpose of this application is to provide a method for using a deep coal mine anchor cable grouting inhibitor.

[0012] To achieve the above purpose, this application provides the following technical solutions:

[0013] A method for using a corrosion inhibitor for grouting of anchor cables in deep coal mines, comprising the following steps:

[0014] (1) Airflow crushing and premixing: Add Cr2O3 and Na3PO4 into an airflow crusher, crush them to D50 ≤ 15 μm, and the mixing degree CV value < 5% to obtain a premixed corrosion inhibitor. The pressure of the airflow crusher is 0.8 MPa;

[0015] (2) Vibration gradient incorporation: Incorporate the premixed corrosion inhibitor into c50 ordinary Portland cement in three times according to the ratios of 50%, 30% and 20%. The water-cement ratio is 0.32. After each incorporation, vibrate with a high-frequency vibrating table for 5 minutes to obtain a grouting sample;

[0016] (3) Molding and curing: Make the grouting sample into a standard test block of 4 cm 3 Place the test block in a thermostatic and humid test chamber and simultaneously start the vibrating table to apply a low-frequency vibration of 0.1 Hz. Cure it through a PLC controller in a rapid setting period and a film-forming period. After the curing is completed, obtain an anchoring sample G;

[0017] (4) Crushing and impregnation: Crush the anchoring sample G, transfer the crushed sample to an extraction container, inject deionized water, and place the extraction container in a thermostatic shaking water bath for continuous impregnation; After the impregnation is completed, filter the extraction liquid, collect the filtrate as a simulated pore liquid, and immerse the pretreated anchor cable specimen in the extraction liquid and let it stand to establish a corrosion medium contact interface to obtain an anchor cable specimen G.

[0018] Preferably, in step (2), the frequency of the high-frequency vibrating table is 100 Hz and the amplitude is 2 mm.

[0019] Preferably, in step (3), the rapid setting period is 0 - 1 d, the temperature gradient rises from 30 °C to 45 °C at a heating rate of 0.625 °C / h, and the humidity decreases from 95% to 80% RH at a rate of 0.625 RH / h. Simultaneously apply an axial pressure of 0.3 MPa and a vibration load of 0.1 Hz.

[0020] Preferably, in step (3), the film-forming period is 1 d - 7 d, the temperature is kept constant at 40 °C and the humidity is 85% RH. Superimpose a confining pressure of 0.5 MPa and a dynamic water pressure of 0.05 Hz to induce Cr 3+ / PO4 3- To form a film by enrichment at the anchor cable-grout interface.

[0021] Preferably, in step (4), the particle size of the crushed sample is ≤5 mm; the anchorage sample G is crushed by a jaw crusher, and the crushed sample is transferred to a sealed polytetrafluoroethylene extraction container, and deionized water is injected according to a solid-liquid ratio of 1:1.67; the container is placed in a constant-temperature shaking water bath, the set temperature is 25±0.5°C, the shaking frequency is 2 Hz, and continuous impregnation is carried out for 48 h; after the impregnation is completed, a vacuum filtration device is used to filter the leaching solution, and the filtrate is collected as the simulated pore fluid, and the pretreated anchor cable specimen is immersed in the leaching solution for 48 h to establish a corrosion medium contact interface, and the anchor cable specimen G is prepared; the vacuum filtration device uses a 0.45 μm mixed cellulose ester filter membrane.

[0022] The third object of the present invention is to provide an application of a deep coal mine anchor cable grouting inhibitor. The inhibitor of the present invention is aimed at the deep coal mine anchor cable grouting and anchoring material, effectively filling a part of the blank of the deep well coal mine inhibitor, enriching the existing product types, and providing more choices for the protection work of deep coal mine mining. The inhibitor can effectively inhibit the corrosion rate of the anchor cable grouting and anchoring material in the harsh environments such as high humidity, high salinity and complex stress in deep coal mines, greatly extending the service life of the anchoring material, and ensuring the stability and safety of the anchor cable structure during the deep coal mine mining process.

[0023] An application of a deep coal mine anchor cable grouting inhibitor, wherein the grouting inhibitor is used in the deep coal mine roadway anchor cable grouting material.

[0024] Beneficial effects:

[0025] (1) The inhibitor (Cr2O3+Na3PO4) of the present invention belongs to an inorganic inhibitor, and the preparation method is simple and only needs to be completed through basic operations such as uniform and gentle stirring, greatly reducing the production difficulty and cost. Moreover, the inhibitor is specifically developed for the deep coal mine anchor cable grouting and anchoring material, effectively filling a part of the blank of the deep well coal mine inhibitor in terms of type, enriching the existing product types, and providing more choices for the protection work of deep coal mine mining.

[0026] (2) The inhibitor of the present invention significantly improves the corrosion inhibition efficiency in simulating the actual deep coal mine environment, can effectively inhibit the corrosion rate of the anchor cable grouting and anchoring material in the harsh environments such as high humidity, high salinity and complex stress in deep coal mines, greatly extending the service life of the anchoring material, and ensuring the stability and safety of the anchor cable structure during the deep coal mine mining process.

[0027] (3) The corrosion inhibitor of the present invention has good compatibility and can be directly incorporated into the anchoring grouting material. A large number of experiments have proved that this corrosion inhibitor will not have any adverse effects on the solidification process of the anchoring material, and to a certain extent, it can promote the optimization of the internal structure of the material, improving the strength of the anchoring material to a certain extent. This characteristic perfectly meets the requirements of the anchor cable grouting anchoring in practical applications and provides solid technical support for the smooth development of deep coal mine mining projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments and descriptions thereof of this application are used to explain this application and do not constitute an improper limitation of this application. Among them:

[0029] Figure 1 is a flowchart of the implementation.

[0030] Figure 2 is a comparison chart of the test results of the anchoring specimens G1, anchoring specimen G2, and anchoring specimen CG in the compressive strength test;

[0031] Figure 3 is the potentiodynamic polarization curve diagram of the anchor cable specimens G1, anchor cable specimen G2, and anchor cable specimen CG;

[0032] Figure 4 is the electrochemical impedance spectroscopy diagram of the anchor cable specimens G1, anchor cable specimen G2, and anchor cable specimen CG. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. Each example is provided by way of explanation of the present application rather than a limitation of the present application. In fact, those skilled in the art will clearly understand that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the embodiments of the present invention should fall within the scope of protection of the embodiments of the present invention.

[0034] Embodiment 1

[0035] Preparation of the pretreated anchor cable specimens includes the following steps:

[0036] S1. Plasma cutting and passivation. Select high-strength anchor cables for coal mine roadway support that meet the GB / T5224-2014 standard, with a yield strength of 1700 MPa, a tensile strength of 2180 MPa, an equivalent diameter of 22 mm, and consisting of 19 steel strands. Use air plasma cutting technology with a current of 80 A and a cutting speed of 1.2 m / min to cut the base material into 10 cm3 For the standard stereoscopic specimen, a micron-scale oxide layer is formed due to the instantaneous high temperature (>1500 °C) on the cutting surface, and a pre-passivated surface is formed after natural cooling, which inhibits the locally induced corrosion during cutting.

[0037] S2. Specimen cleaning: Place the specimen in a supercritical CO2 reactor with a pressure of 10 MPa and a temperature of 50 °C and circulate for cleaning for 20 min. Utilize the strong permeability and low surface tension of CO2 to completely strip the oil stains and oxide skins on the surface of the specimen, avoiding secondary pollution caused by traditional chemical cleaning.

[0038] S3. Encapsulation and polishing: After implementing reliable electrical connection between the top end of the specimen and the copper wire, fix it in a silicone mold, control the effective acting area of the bottom surface to be 1 cm 2 . After implementing interface sealing with silicone, use a pulsed electromagnetic field with a frequency of 5 kHz and a magnetic field intensity of 0.5 T to drive diamond abrasives (particle size 10 μm) to perform non-contact polishing on the exposed surface until the surface roughness Ra < 0.2 μm, making the working surface smooth and visually detecting no surface defects such as oxidation pits.

[0039] S4. Preservation for standby: After the specimen with surface treatment is alternately rinsed with deionized water and absolute ethanol, transfer it to a vacuum drying oven for drying treatment (60 °C) to obtain a pretreated anchor cable specimen, and finally encapsulate it in a vacuum storage device with an argon atmosphere for standby.

[0040] Example 2

[0041] The preparation method of the anchoring specimen G1 and the anchor cable specimen G1 includes the following steps:

[0042] S1. Airflow crushing and premixing: Put Cr2O3 and Na3PO4 into an airflow crusher with a pressure of 0.8 MPa according to the ratio in Table 1, and utilize the collision of high-speed airflows to achieve ultrafine crushing and uniform mixing of the particles, crush to D50 ≤ 15 μm, and the mixing degree CV value < 5% to obtain a premixed corrosion inhibitor.

[0043] S2. Vibration gradient incorporation: Incorporate the premixed corrosion inhibitor into c50 ordinary Portland cement (water-cement ratio 0.32) in three times according to the ratios of 50% - 30% and 20%. After each incorporation, vibrate with a high-frequency vibrating table with a frequency of 100 Hz and an amplitude of 2 mm for 5 min to promote the directional migration of the corrosion inhibitor along the pore network of the slurry to make a grouting specimen.

[0044] S3. Molding and curing: Make the grouting specimen into a standard test block of 4 cm 3 . Place the test block in a thermostatic and humid test chamber and perform dynamic curing in the following two stages:

[0045] 1) Quick setting period (0 - 1 d), the temperature gradient rises from 30 °C to 45 °C (simulating deep geothermal temperature), humidity 95% → 80% RH, simultaneously apply an axial pressure of 0.3 MPa and a vibration load of 0.1 Hz to accelerate the densification of the slurry;

[0046] 2) Inhibitor film formation period (1 d - 7 d), keep the temperature constant at 40 °C and humidity at 85% RH, superimpose a confining pressure of 0.5 MPa and a dynamic water pressure of 0.05 Hz (simulating the infiltration of fissure water), and induce Cr 3+ / PO4 3- to form a film enriched at the anchor cable - slurry interface;

[0047] After the curing is completed, place the specimen in a vacuum drying oven with a vacuum degree ≤ 0.1 MPa and dry for 24 h to obtain the anchored specimen G1, which is sealed and stored in an environment of 4 °C for later use. Conduct a compressive strength test on the specimen using a compressive strength tester to ensure that its mechanical properties meet the requirements.

[0048] S4. Crushing and impregnation: Place the anchored specimen G1 cured for 7 days in a jaw crusher, screen it through a standard sieve with a pore size of 5 mm after crushing, and collect 300 g of crushed samples with a particle size ≤ 5 mm to ensure the uniformity of the crushed samples. Transfer 300 g of the crushed samples to a sealed polytetrafluoroethylene extraction container, inject deionized water according to a solid - liquid ratio of 1:1.67; place the container in a constant - temperature shaking water bath, set the temperature at 25 ± 0.5 °C, the shaking frequency at 2 Hz, and continuously impregnate for 48 h; after the impregnation is completed, use a vacuum filtration device (0.45 μm mixed cellulose ester filter membrane) to filter the extract, collect the filtrate as the simulated pore fluid, immerse the pretreated anchor cable specimen in the extract for 48 h to establish a corrosion medium contact interface, and obtain the anchor cable specimen G1, which is sealed and stored in an environment of 4 °C for subsequent Tafel polarization curve and electrochemical impedance spectroscopy tests. As Figure 1 shown.

[0049] Table 1 shows the formula of the anchor cable grouting anchoring composite inhibitor

[0050]

[0051] Example 3

[0052] The preparation method of the anchored specimen G2 and the anchor cable specimen G2 includes the following steps:

[0053] S1. Air - flow crushing and premixing: Put Cr2O3 and Na3PO4 into an air - flow crusher with a pressure of 0.8 MPa according to the ratio in Table 1, use the high - speed air flow collision to achieve ultra - fine crushing and uniform mixing of the particles, crush them to D50 ≤ 15 μm, and the mixing degree CV value < 5%.

[0054] S2. Vibration gradient incorporation: The premixed corrosion inhibitor is incorporated into the C50 ordinary Portland cement (water-cement ratio 0.32) in three times according to the ratios of 50%-30% and 20%. After each incorporation, it is vibrated for 5 minutes by a high-frequency vibrating table with a frequency of 100 Hz and an amplitude of 2 mm to promote the directional migration of the corrosion inhibitor along the pore network of the paste, and a grouting sample is made.

[0055] S3. Molding and curing: The grouting sample is made into standard test blocks of 4 cm 3 . The test blocks are placed in a thermostatic and humidified test chamber and cured dynamically in two stages:

[0056] 1) Rapid setting period (0-1d), the temperature gradient rises from 30°C to 45°C (simulating deep geothermal temperature), the humidity is 95%→80%RH, and an axial pressure of 0.3 MPa and a vibration load of 0.1 Hz are applied synchronously to accelerate the densification of the paste;

[0057] 2) Corrosion inhibitor film-forming period (1d-7d), constant temperature of 40°C, humidity of 85% RH, superimposed with a confining pressure of 0.5 MPa and a dynamic water pressure of 0.05 Hz (simulating the infiltration of fissure water), inducing Cr 3+ / PO4 3- to form a film enriched at the anchor cable-paste interface;

[0058] After curing, the specimens are placed in a vacuum drying oven with a vacuum degree ≤0.1 MPa and dried for 24 h. The anchor specimens G2 are prepared and stored sealed in an environment of 4°C for later use. The compressive strength of the specimens is tested by a compressive strength tester to ensure that their mechanical properties meet the requirements.

[0059] S4. Crushing and impregnation: The anchor specimen G1 cured for 7 days is placed in a jaw crusher, crushed, and screened through a standard sieve with a pore size of 5 mm. 300 g of crushed samples with a particle size ≤5 mm are collected to ensure the uniformity of the crushed samples. The 300 g of crushed samples are transferred to a sealed polytetrafluoroethylene extraction container, and deionized water is injected according to a solid-liquid ratio of 1:1.67; the container is placed in a thermostatic shaking water bath, the temperature is set at 25±0.5°C, the shaking frequency is 2 Hz, and continuous impregnation is carried out for 48 h; after impregnation, the extraction solution is filtered using a vacuum filtration device (0.45 μm mixed cellulose ester filter membrane), and the filtrate is collected as the simulated pore fluid. The pretreated anchor cable specimens are immersed in the extraction solution for 48 h to establish a corrosion medium contact interface, and the anchor cable specimens G2 are prepared and stored sealed in an environment of 4°C for subsequent Tafel polarization curve and electrochemical impedance spectroscopy tests.

[0060] Example 4

[0061] Preparation of the anchor specimen CG and the anchor cable specimen CG, including the following steps:

[0062] S1. Grouting molding and curing. Without adding corrosion inhibitors, place the grouted specimens (4 cm³ standard test blocks) in a thermostatic and humid environment test chamber, and conduct dynamic curing in two stages:

[0063] 1) Rapid setting period (0 - 1d): The temperature gradient rises from 30°C to 45°C (simulating deep geothermal temperature), the humidity is 95% → 80%RH, and simultaneously apply an axial pressure of 0.3 MPa and a vibration load of 0.1 Hz to accelerate the densification of the slurry;

[0064] 2) Control corrosion inhibitor film - forming period (1d - 7d): Keep the temperature at 40°C and the humidity at 85%RH, and superimpose a confining pressure of 0.5 MPa and a dynamic water pressure of 0.05Hz (simulating the infiltration of fissure water);

[0065] After curing, place the specimens in a vacuum drying oven with a vacuum degree ≤ 0.1 MPa for 24h to obtain the anchored specimens CG. Conduct compressive strength tests on the specimens using a compressive strength tester to ensure that their mechanical properties meet the requirements.

[0066] S2. Impregnation. Collect the in - situ leachate from deep mines as the immersion liquid. After dynamically impregnating the pretreated anchor cable specimens for 48h, obtain the anchor cable specimens CG for subsequent Tafel polarization curve and electrochemical impedance spectroscopy tests.

[0067] Characterization and analysis:

[0068] (1) Strength test

[0069] Conduct compressive strength tests on the anchored specimens G1, G2 and the control anchored specimen CG respectively. The results are as Figure 2 shown. From Figure 2 it can be seen that at the 1 - day curing time, there is no significant change in the anchored specimens G1 and G2 compared with the control anchored specimen CG. However, at the 7 - day curing time, the compressive strength of the anchored specimen G1 is significantly higher than that of the control anchored specimen CG, and there is no significant change in the compressive strength of the anchored specimen G2. Therefore, it can be determined that this type of corrosion inhibitor has no adverse effects on the anchoring solidification and strength, and the strength of the anchored specimen G1 is higher than that of the control group, meeting the characteristics of high strength in the anchor cable support of deep coal mines. It is a suitable corrosion inhibitor.

[0070] (2) Potentiodynamic polarization curve test

[0071] Conduct potentiodynamic polarization curve tests on the anchor cable specimens G1 in Example 2, the anchor cable specimens G2 in Example 3 and the anchor cable specimens CG in Example 4. The results are as Figure 3 shown.

[0072] From Figure 3It can be seen that the corrosion potentials of the anchor cable specimens G1 and G2 with the addition of corrosion inhibitors have shifted positively to varying degrees, but the fluctuation does not exceed 0.1 V, indicating that the addition of corrosion inhibitors has little effect on the corrosion tendency. The corrosion current densities of the specimens with the addition of corrosion inhibitors have all decreased significantly, indicating that the addition of corrosion inhibitors reduces the corrosion rate of the anchor cable. Among them, the reduction effect of the anchor cable specimen G1 is the most obvious, and the current density decreases from 2.29×10 -4 A / cm 2 to 2.25×10 -5 A / cm 2 , with a decrease of up to 90.2%.

[0073] (3) Electrochemical impedance spectroscopy test

[0074] Electrochemical impedance spectroscopy test is a key technology for studying electrochemical systems, which measures the response of the system under the perturbation of AC signals at different frequencies to obtain impedance information. A three-electrode system is commonly used in the test. A small-amplitude AC voltage is superimposed on the DC potential and applied between the working electrode and the reference electrode, and the AC current of the working electrode is measured. The frequency is changed and the data is recorded to obtain the electrochemical impedance spectrum. Its data is presented in Nyquist diagrams and Bode diagrams, and circuit element parameters such as resistance and capacitance are obtained through equivalent circuit fitting. These parameters can reflect the physical and chemical processes of the system. EIS is widely used in research fields such as batteries, corrosion, electrocatalysis, and sensors, providing key information for related research.

[0075] Using a CS310 model electrochemical workstation produced by Wuhan Kost, the reference electrode and the auxiliary electrode are respectively selected as the saturated calomel electrode and the platinum wire. To ensure the applicability of the invention, the conductive solution is selected as the roof watering in the coal mine site. The test is carried out with a frequency interval of 0.01 - 100000 Hz and an amplitude of ±3 mV at the self-corrosion potential.

[0076] The equivalent circuit of the specimen is fitted. Rs is the solution resistance, Rf is the double-layer capacitance, CPEf is the protective film capacitance, and Rct is the charge transfer resistance. Figure 4 The middle curve is the Nyquist diagram of the electrochemical impedance spectrum. It can be seen from Figure 4 that the impedance radii of the anchor cable specimens G1 and G2 are significantly larger than those of the anchor cable specimen CG. Since the increase in the impedance radius indicates an improvement in the corrosion resistance, it is thus proved that the anchor cable specimens G1 and G2 have better corrosion resistance, and the corrosion inhibitor of the present invention plays a good role.

[0077] The above strength tests show that after adding the corrosion inhibitor Cr2O3 + Na3PO4 of the present invention, the compressive strength of the anchored specimen G1 at 7 days of curing is significantly higher than that of the control group, and this corrosion inhibitor has no adverse effect on the anchoring solidification and strength, meeting the characteristics of high strength in deep coal mine cable bolt support. The potentiodynamic polarization curve test shows that after adding the corrosion inhibitor of the present invention, the corrosion current density of the cable bolt decreases significantly, and the decrease rate of the cable bolt specimen G1 is as high as 90.2%, effectively reducing the corrosion rate of the cable bolt. In the electrochemical impedance spectroscopy test, the impedance radii of the cable bolt specimens G1 and G2 are significantly increased compared with the control group, proving that they have better corrosion resistance and the corrosion inhibitor works well. This cable bolt grouting and anchoring material has high strength and excellent corrosion resistance, providing a reliable solution for deep coal mine cable bolt support.

[0078] Cr2O3 plays a corrosion inhibition role in the alkaline grouting environment (pH≈12) of deep coal mines through the formation and self-repair mechanism of the passive film: The Cr released by its dissolution 3+ reacts with OH¯ to form a dense Cr(OH)3 or Cr2O3·nH2O passive film, physically blocking the penetration of Cl¯, O2 and H2O; at the same time, Cr 3+ maintains the integrity by dynamically regenerating the film layer through redox. Na3PO4 inhibits corrosion through multiple mechanisms: PO4 3 ¯ reacts with Fe 2+ / Fe 3+ to form a FePO4 or FeOOH-PO4 precipitation film, covering the anodic active sites; its chemical adsorption forms a monolayer to inhibit the oxygen reduction reaction (cathodic process), and reduces the risk of pitting corrosion through competitive adsorption of Cl¯. Experiments show that adding Cr2O3 or Na3PO4 alone can reduce the corrosion current density by 60% and 45% respectively, but there are potential problems of local defects in the film layer or penetration of Cl¯.

[0079] As a corrosion inhibitor in the cable bolt, chromium oxide in the corrosion inhibitor plays a role through multi-dimensional mechanisms. According to the electrochemical test results, after adding the corrosion inhibitor to the specimen, not only the corrosion resistance is significantly improved, but also the compressive strength is increased to a certain extent. Among them, Cr2O3 may act as a crystal nucleus to promote the formation of C-S-H gel, improve the compactness of concrete, and indirectly enhance the durability; in addition, Cr2O3 partially dissolves in the alkaline concrete pore solution, releasing Cr 3+ ions, which react with OH¯ to form chromium hydroxide (Cr(OH)3) or oxygen-containing hydroxide (CrOOH), forming a dense passive film (Cr2O3·xH2O) on the surface of the steel bar. This film physically isolates Cl¯, O2 and H2O, significantly inhibiting the electrochemical corrosion reaction. Sodium phosphate (Na3PO4), as a corrosion inhibitor for steel bars in concrete, mainly delays the corrosion of steel bars through multiple mechanisms such as chemical passivation, pH adjustment, chloride ion (Cl¯) fixation and electrochemical inhibition. Sodium phosphate may delay the early hydration of cement (reacting with Ca2+ Combined to form Ca3(PO4)2, but can promote the densification of C-S-H gel in the later stage; after sodium phosphate dissolves in the concrete pore solution (high alkaline environment, pH>12.5), PO4 3 ¯ ions are released. PO4 3 ¯ reacts with the Fe 2+ / Fe 3+ on the surface of the steel bar to generate a dense iron phosphate (FePO4·nH2O) or iron hydroxyphosphate (FeOOH-PO4) composite passivation film. The phosphate passivation film is more stable than the traditional Fe2O3 / Fe(OH)3 film, especially with stronger resistance to local corrosion in the presence of Cl¯. The passivation film can repair local damaged areas (such as Cl¯ intrusion points) and inhibit the expansion of pitting corrosion.

[0080] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0081] The above are only the preferred embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for using a corrosion inhibitor for anchor cable grouting in deep coal mines, characterized in that, The grouting corrosion inhibitor is composed of Cr2O3 and Na3PO4, and the mass ratio of Cr2O3 to Na3PO4 is 1-5:

1. Its usage method includes the following steps: (1) Airflow crushing and premixing: Add Cr2O3 and Na3PO4 into an airflow crusher, crush them to D50≤15μm, and the mixing degree CV value <5% to obtain a premixed corrosion inhibitor. The pressure of the airflow crusher is 0.8 MPa; (2) Vibration gradient incorporation: Incorporate the premixed corrosion inhibitor into c50 ordinary Portland cement in three times, with a water-cement ratio of 0.

32. After each incorporation, vibrate with a high-frequency vibration table for 5 minutes to obtain a grouting sample; (3) Molding and curing. Make the grouting specimens into standard test blocks with a size of 4 cm 3 . Place the test blocks in a thermostatic and humid test chamber, simultaneously start the vibrating table to apply low-frequency vibration at 0.1 Hz, and cure them through the PLC controller in the rapid setting period and the film-forming period. After the curing is completed, the anchoring specimen G is obtained; (4) Crushing and impregnation: Crush the anchor specimen G, transfer the crushed sample to an extraction container, inject deionized water, and place the extraction container in a constant-temperature shaking water bath for continuous impregnation; after the impregnation is completed, filter the extraction liquid, collect the filtrate as a simulated pore fluid, immerse the pretreated anchor cable specimen in the extraction liquid and let it stand to establish a corrosion medium contact interface to obtain the anchor cable specimen G.

2. The method for using a deep coal mine anchor cable grouting corrosion inhibitor according to claim 1, characterized in that In step (2), the frequency of the high-frequency vibration table is 100 Hz, and the amplitude is 2 mm.

3. The method for using the deep coal mine anchor cable grouting corrosion inhibitor according to claim 1, characterized in that, In step (3), the rapid setting period is 0-1 d, the temperature gradient rises from 30°C to 45°C at a heating rate of 0.625°C / h, and the humidity decreases from 95% to 80% RH at a rate of 0.625RH / h. At the same time, apply an axial pressure of 0.3 MPa and a vibration load of 0.1 Hz.

4. The method for using a deep coal mine anchor cable grouting corrosion inhibitor according to claim 1, characterized in that In step (3), the film-forming period is 1 d to 7 d, with a constant temperature of 40 °C and a humidity of 85% RH, and a confining pressure of 0.5 MPa and a dynamic water pressure of 0.05 Hz are superimposed to induce Cr 3+ / PO4 3- to form a film at the interface between the anchor cable and the grout.

5. The method for using the deep coal mine anchor cable grouting corrosion inhibitor according to claim 1, characterized in that, In step (4), the particle size of the crushed sample ≤5 mm; use a jaw crusher to crush the anchor specimen G, transfer the crushed sample to a sealed polytetrafluoroethylene extraction container, and inject deionized water according to a solid-liquid ratio of 1:1.67; place the container in a constant-temperature shaking water bath, set the temperature to 25±0.5°C, the shaking frequency to 2 Hz, and continuously impregnate for 48 h; after the impregnation is completed, use a vacuum filtration device to filter the extraction liquid, collect the filtrate as a simulated pore fluid, immerse the pretreated anchor cable specimen in the extraction liquid for 48 h, establish a corrosion medium contact interface to obtain the anchor cable specimen G; the vacuum filtration device uses a 0.45μm mixed cellulose ester filter membrane.

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