A composite corrosion inhibitor and its application in inhibiting corrosion of stainless steel

Abstract

The present application belongs to the technical field of inhibiting metal corrosion, and particularly relates to a composite corrosion inhibitor and application thereof in inhibiting corrosion of stainless steel in industrial circulating cooling water. The composite corrosion inhibitor provided by the present application comprises a double quaternary ammonium salt and a hydrolyzed polymaleic anhydride, the mass ratio of the double quaternary ammonium salt and the hydrolyzed polymaleic anhydride is (2.0-2.7):1, the structural formula of the double quaternary ammonium salt is shown as formula 1, and the structural formula of the hydrolyzed polymaleic anhydride is shown as formula 2. The present application is prepared by compounding the double quaternary ammonium salt and the hydrolyzed polymaleic anhydride, and utilizes the corrosion-inhibiting passivation film formed by the double quaternary ammonium salt and the hydrolyzed polymaleic anhydride on the surface of the stainless steel to change the hydrophobicity of the surface of the stainless steel, reduce the roughness of the surface of the stainless steel, and greatly slow down the deposition of the biofilm and the deposition of the fouling substances. The composite corrosion inhibitor provided by the present application has a stainless steel corrosion inhibition rate of 70-80% in circulating water, a sterilization rate of greater than or equal to 90%, and a scale inhibition rate of greater than or equal to 95%.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion inhibition technology, specifically relating to a composite corrosion inhibitor and its application in inhibiting stainless steel corrosion. Background Technology

[0002] Thermal power plants account for over 80% of the nation's total electricity generation, while their water consumption accounts for approximately 30% of total industrial water consumption. Furthermore, circulating cooling water systems account for about 60%-80% of the total water consumption within thermal power plants. To effectively address water scarcity, China has designated thermal power plants as a key area for industrial utilization of municipal reclaimed water.

[0003] Since the 1920s, foreign countries have seen engineering practices of using municipal reclaimed water for industrial circulating cooling water systems, with the United States having the most examples. For instance, the effluent from the Bamberg Reclaimed Water Plant in California is used as circulating cooling water in a thermal power plant, with a concentration ratio of 4 times. In Denton, municipal wastewater undergoes advanced treatment and is used as cooling water and boiler feedwater at the Denton Power Plant. my country began researching municipal wastewater reuse technology in the 1980s. Water-scarce cities such as Beijing, Tianjin, Qingdao, and Xi'an have successively implemented municipal reclaimed water reuse projects. In June 2000, Beijing Huaneng Power Plant used secondary effluent from the Gaobeidian Wastewater Treatment Plant as feedwater for its circulating cooling water system. Beijing Datang International Gaojing Thermal Power Plant and Beijing Jingneng Thermal Power Co., Ltd., among others, have also successively implemented municipal reclaimed water reuse projects.

[0004] However, this has led to an increasingly prominent problem of metal corrosion and scaling caused by circulating water. Circulating water is characterized by high levels of organic matter, high levels of suspended solids, and high levels of Cl-. - SO4 2- These characteristics exacerbate the tendency of microbial corrosion in pipes within circulating water systems. Studies estimate that corrosion costs in my country in 2014 amounted to approximately 2.1278 trillion RMB (about 310 billion USD), representing about 3.34% of GDP. To reduce losses caused by corrosion, researchers both domestically and internationally have explored various methods for protecting metals from corrosion, primarily including: developing new corrosion-resistant alloys; electrochemical protection (cathode protection, anodic protection); surface treatment; adding corrosion inhibitors; and coating protection. Among these, adding corrosion inhibitors is one of the most widely used methods, offering advantages such as low dosage, simple operation, significant effects, and low cost.

[0005] However, in practical applications, commercially available corrosion inhibitors currently have poor corrosion inhibition effects and cannot effectively prevent metal corrosion and scaling problems caused by circulating water. Summary of the Invention

[0006] The purpose of this invention is to provide a composite corrosion inhibitor and its application in inhibiting the corrosion of stainless steel in industrial circulating cooling water. The composite corrosion inhibitor provided by this invention can effectively delay the corrosion of stainless steel pipes by circulating water when added to industrial circulating cooling water.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a composite corrosion inhibitor comprising a bis-quaternary ammonium salt and hydrolyzed polymaleic anhydride; wherein the mass ratio of the bis-quaternary ammonium salt to the hydrolyzed polymaleic anhydride is (2.0-2.7):1;

[0009] The structural formula of the bisquaternary ammonium salt is shown in Formula 1:

[0010]

[0011] In Equation 1: R is C m H 2m+1 C m H 2m+1 CH2CO2 or C m H 2m+1 COOCH2CH2, 8≤m≤13; Y is CH2, NCH3, S or O;

[0012] The structural formula of the hydrolyzed polymaleic anhydride is shown in Formula 2:

[0013]

[0014] In Equation 2: 8≤m≤13, 8≤n≤13.

[0015] Preferably, it also includes water; in the composite corrosion inhibitor, the mass concentration of the bisquaternary ammonium salt is 3.0-4.0 g / L, and the mass concentration of the hydrolyzed polymaleic anhydride is 1.5 g / L.

[0016] This invention provides the application of the composite corrosion inhibitor described in the above technical solution in inhibiting the corrosion of stainless steel, wherein the service environment of the stainless steel includes industrial circulating cooling water.

[0017] Preferably, the volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is 1:(50-100).

[0018] Preferably, the volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is 1:(60-95).

[0019] Preferably, the industrial circulating cooling water is reclaimed water that has been concentrated 3 to 5 times, and the water quality indicators of the reclaimed water include: pH value of 7.55±0.12; conductivity of 885±12.65 μS·cm. -1The total hardness is 244.5 ± 3.25 mg·L. -1 Cl - The content was 108.12 ± 2.76 mg·L. -1 SO4 2- The content was 177.0 ± 3.08 mg·L. -1 NO3 - The content was 98.55 ± 2.24 mg·L. -1 ;PO4 3- The content was 1.24 ± 0.08 mg·L. -1 NH4 + The content was 4.55 ± 0.22 mg·L. -1 COD Cr It was 55.7 ± 1.32 mg·L. -1 The BOD5 content was 45.3 ± 1.85 mg·L. -1 Turbidity was 1.62 ± 0.11 NTU; K + The content was 29.55 ± 0.83 mg·L. -1 Na + The content was 87.37 ± 2.33 mg·L. -1 ;Ca 2+ The content was 180.94 ± 2.63 mg·L. -1 ;Mg 2+ The content was 63.42 ± 1.62 mg·L. -1 Fe 3+ The content is 0.23±0.02 mg·L. -1 Al 3+ The content was 0.76 ± 0.17 mg·L. -1 ;Si 2+ 27.12±0.73 mg·L -1 Mn 2+ The content is 0.20±0.04 mg·L. -1 Zn 2+ The content was 2.84 ± 0.23 mg·L. -1 The total bacterial count was 3.43 × 10⁻⁶. 7 ±5.82×10 5 L -1 .

[0020] Preferably, the stainless steel material includes SS304, SS316L and SS317L.

[0021] Preferably, the application includes the following steps:

[0022] The composite corrosion inhibitor described in the above technical solution is intermittently added to the industrial circulating cooling water, and the resulting industrial circulating cooling water containing the composite corrosion inhibitor circulates in the stainless steel pipeline for circulating cooling.

[0023] Preferably, the interval period for the intermittent addition is 10 to 20 days.

[0024] Preferably, the concentration ratio of the industrial circulating cooling water is 3 to 5 times.

[0025] This invention provides a composite corrosion inhibitor comprising a bis-quaternary ammonium salt and hydrolyzed polymaleic anhydride; the mass ratio of the bis-quaternary ammonium salt to the hydrolyzed polymaleic anhydride is (2.0–2.7):1; the structural formula of the bis-quaternary ammonium salt is shown in Formula 1, and the structural formula of the hydrolyzed polymaleic anhydride is shown in Formula 2. In this invention, the bis-quaternary ammonium salt molecule contains two positively charged N atoms. + Through induction, the positive charge density on the quaternary nitrogen in the molecule increases, which is more conducive to the adsorption of bactericide molecules on the surface of bacteria in circulating cooling water, thereby changing the permeability of the cell wall and causing bacterial rupture. On the other hand, the quaternary ammonium salt is adsorbed onto the negatively charged bacterial surface and penetrates into the lipid and protein layers of the bacterial cell, leading to enzyme inactivation and protein denaturation. Due to the combined effect of these two actions, the quaternary ammonium salt composite bactericide has a strong bactericidal ability. Meanwhile, the hydrolyzed polymaleic anhydride molecule contains multiple carboxylic acid groups [-COOH], which carry a negative charge after ionization in water. When negatively charged crystalline particles, such as CaCO3, in circulating cooling water are adsorbed and surrounded by the polymer's high-valence anions, the increased surface negative charge leads to increased intermolecular repulsion, inhibiting scaling. Simultaneously, the hydrolyzed polymaleic anhydride structure contains multiple carbonyl O atoms and Ca atoms on the crystal plane. 2+ Adsorption effectively prevents the continued growth of fouling crystals. Furthermore, hydrolyzed polymaleic anhydride molecules distort the fouling lattice, forming soft scale that is easily washed away by water, thus achieving a scale inhibition effect. This invention, through the combination of a quaternary ammonium salt composite bactericide and hydrolyzed polymaleic anhydride, forms a corrosion-inhibiting passivation film on the stainless steel surface, altering the surface's hydrophobicity, reducing its roughness, and significantly slowing down biofilm deposition and scale buildup.

[0026] This invention provides the application of the composite corrosion inhibitor described above in inhibiting the corrosion of stainless steel, wherein the stainless steel is used in industrial circulating cooling water. The composite corrosion inhibitor provided by this invention does not require the addition of external alkalis or complexing agents when inhibiting the corrosion of stainless steel in circulating cooling water, making operation simple and avoiding secondary pollution. Results from the embodiments show that the composite corrosion inhibitor provided by this invention achieves a corrosion inhibition rate of 70-80% for stainless steel in circulating water, a sterilization rate ≥90%, and a scale inhibition rate ≥95%. Detailed Implementation

[0027] This invention provides a composite corrosion inhibitor comprising a bis-quaternary ammonium salt and hydrolyzed polymaleic anhydride; wherein the mass ratio of the bis-quaternary ammonium salt to the hydrolyzed polymaleic anhydride is (2.0-2.7):1;

[0028] The structural formula of the bisquaternary ammonium salt is shown in Formula 1:

[0029]

[0030] In Equation 1: R is C m H 2m+1 C m H 2m+1 CH2CO2 or C m H 2m+1 COOCH2CH2, 8≤m≤13; Y is CH2, NCH3, S or O;

[0031] The structural formula of the hydrolyzed polymaleic anhydride is shown in Formula 2:

[0032]

[0033] In Equation 2: 8≤m≤13, 8≤n≤13.

[0034] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0035] The composite corrosion inhibitor provided by this invention comprises a bis-quaternary ammonium salt. The structural formula of the bis-quaternary ammonium salt is shown in Formula 1:

[0036]

[0037] In Equation 1: R is C m H 2m+1 C m H 2m+1 CH2CO2 or C m H 2m+1 COOCH2CH2, 8≤m≤13; Y is CH2, NCH3, S or O, and m is an integer.

[0038] In this invention, the quaternary ammonium salt is preferably used in the form of a quaternary ammonium salt liquid bactericide, which includes a quaternary ammonium salt and a solvent.

[0039] The bisquaternary ammonium salt provided by this invention is a cationic surfactant with higher surface activity, better solubility, low Krafft point, good solubilizing ability, high wettability and good synergistic effect.

[0040] The composite corrosion inhibitor provided by this invention includes hydrolyzed polymaleic anhydride (HPMA).

[0041] In this invention, the structural formula of the hydrolyzed polymaleic anhydride is shown in Formula 2:

[0042]

[0043] In Equation 2: 8≤m≤13, 8≤n≤13.

[0044] In this invention, the molecular formula of the hydrolyzed polymaleic anhydride is C0. 4m+4n H 4m+2n O 4m+3n , where 8≤m≤13, 8≤n≤13, and m and n are both integers.

[0045] In this invention, HPMA molecules contain multiple carboxyl oxygen atoms, which readily become adsorption sites for the interaction between scale inhibitors and crystal faces, thereby effectively preventing the continued growth of these crystal faces. In addition, HPMA molecules cause the crystal lattice to be distorted, forming soft scale that is easily washed away by water flow, thus achieving the scale inhibition effect.

[0046] In this invention, the mass ratio of the bisquaternary ammonium salt composite bactericide to hydrolyzed polymaleic anhydride is preferably (2.0-2.7):1, more preferably (2.1-2.6):1.

[0047] The composite corrosion inhibitor provided by this invention preferably further includes water. In this invention, the water is used as a diluent.

[0048] In this invention, the mass concentration of the bisquaternary ammonium salt in the composite corrosion inhibitor is preferably 3.0-4.0 g / L, and the mass concentration of the hydrolyzed polymaleic anhydride is preferably 1.5 g / L.

[0049] The present invention does not have special requirements for the preparation method of the composite corrosion inhibitor; it is sufficient to mix the bisquaternary ammonium salt composite bactericide and the hydrolyzed polymaleic anhydride evenly. In the present invention, when the composite corrosion inhibitor further includes water, it is preferable to mix the bisquaternary ammonium salt composite bactericide, the hydrolyzed polymaleic anhydride, and the water evenly.

[0050] This invention provides the application of the composite corrosion inhibitor described in the above technical solution in inhibiting the corrosion of stainless steel, wherein the service environment of the stainless steel includes industrial circulating cooling water.

[0051] In this invention, the composite corrosion inhibitor preferably comprises the bisquaternary ammonium salt composite bactericide, the hydrolyzed polymaleic anhydride, and water; in the composite corrosion inhibitor, the mass concentration of the bisquaternary ammonium salt is preferably 3.0-4.0 g / L, and the mass concentration of the hydrolyzed polymaleic anhydride is preferably 1.5 g / L.

[0052] In this invention, the industrial circulating cooling water is preferably reclaimed water, and the water quality indicators of the reclaimed water preferably include: a pH value of 7.55±0.12; and a conductivity of 885±12.65 μS·cm. -1 The total hardness is 244.5 ± 3.25 mg·L. -1 Cl - The content was 108.12 ± 2.76 mg·L. -1 SO4 2- The content was 177.0 ± 3.08 mg·L. -1 NO3 - The content was 98.55 ± 2.24 mg·L. -1 ;PO4 3- The content was 1.24 ± 0.08 mg·L. -1 NH4 + The content was 4.55 ± 0.22 mg·L. -1 COD Cr It was 55.7 ± 1.32 mg·L. -1 The BOD5 content was 45.3 ± 1.85 mg·L. -1 Turbidity was 1.62 ± 0.11 NTU; K + The content was 29.55 ± 0.83 mg·L. -1 Na + The content was 87.37 ± 2.33 mg·L. -1 ;Ca 2+ The content was 180.94 ± 2.63 mg·L. -1 ;Mg 2+ The content was 63.42 ± 1.62 mg·L. -1 Fe 3+ The content is 0.23±0.02 mg·L. -1 Al 3+ The content was 0.76 ± 0.17 mg·L. -1 ;Si 2+ 27.12±0.73 mg·L -1 Mn 2+ The content is 0.20±0.04 mg·L. -1 Zn 2+ The content was 2.84 ± 0.23 mg·L. -1 The total bacterial count was 3.43 × 10⁻⁶. 7 ±5.82×10 5 L -1 .

[0053] This invention does not have specific requirements regarding the source of the reclaimed water. In a specific embodiment of this invention, the reclaimed water is obtained from a municipal wastewater treatment plant after secondary treatment.

[0054] In this invention, the stainless steel material includes SS304, SS316L and SS317L.

[0055] In this invention, the volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is preferably 1:(50-100), more preferably 1:(60-95), and specifically preferably 1:95, 1:90, 1:85, 1:80, 1:75, 1:70, 1:65 or 1:60.

[0056] In this invention, when the volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is preferably within the above-mentioned range, the composite corrosion inhibitor can effectively delay the corrosion of stainless steel pipes by the circulating water. However, if the volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is not within the above-mentioned range, both excessively large and excessively small ratios will reduce the corrosion inhibition efficiency of stainless steel in the circulating water solution.

[0057] In this invention, the application preferably includes the following steps:

[0058] The composite corrosion inhibitor described in the above technical solution is intermittently added to the industrial circulating cooling water, and the resulting industrial circulating cooling water containing the composite corrosion inhibitor circulates in the stainless steel pipeline for circulating cooling.

[0059] In this invention, the intermittent period of the intermittent addition is preferably 10 to 20 days, more preferably 10 to 15 days.

[0060] In this invention, the concentration ratio of the industrial circulating cooling water is preferably 3 to 5 times, more preferably 3 times, 4 times, or 5 times. In this invention, the concentration ratio of the industrial circulating cooling water refers to the concentration that occurs during the circulating cooling process. When the industrial circulating cooling water reaches the specified concentration ratio during use, it needs to be replaced.

[0061] The composite corrosion inhibitor provided by this invention can effectively delay the corrosion of stainless steel pipes by circulating water, achieving a corrosion inhibition rate of 70-80%, a sterilization rate of ≥90%, and a scale inhibition rate of ≥95% for stainless steel in the circulating water. When the circulating water concentration ratio is 3-5 times, it ensures that the service life of the stainless steel pipe is ≥10 years, preferably 10-20 years.

[0062] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0063] Example 1

[0064] A composite corrosion inhibitor was obtained by mixing a quaternary ammonium salt composite bactericide, hydrolyzed polymaleic anhydride, and water. The mass concentration of the quaternary ammonium salt in the composite corrosion inhibitor was 3.0 g / L, and the mass concentration of the hydrolyzed polymaleic anhydride was 1.5 g / L.

[0065] Example 2

[0066] A composite corrosion inhibitor was obtained by mixing a quaternary ammonium salt composite bactericide, hydrolyzed polymaleic anhydride, and water. The mass concentration of the quaternary ammonium salt in the composite corrosion inhibitor was 4.0 g / L, and the mass concentration of the hydrolyzed polymaleic anhydride was 1.5 g / L.

[0067] Test Example 1

[0068] I. Reaction: Municipal reclaimed water, concentrated three times, was added to the reactor as circulating water. The composite corrosion inhibitor provided in Example 1 was added, with a ratio of composite corrosion inhibitor to circulating water solution of 1:100. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grits of 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. The pieces were then soaked in acetone for 10 minutes to remove grease, and then soaked in anhydrous ethanol for 10 minutes to remove moisture before being placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating plate method, and the reaction was carried out at 200 rpm for 24 hours at a temperature of 20–25°C.

[0069] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve testing; the corrosion inhibition efficiency of the composite agent on stainless steel was determined by Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0070] In Example 1 of this invention, the composite corrosion inhibitor and municipal reclaimed water (concentrated three times) were used as circulating water at a volume ratio of 1:100. After 24 hours of experimentation, the corrosion inhibition efficiency for stainless steel pipes was 65%, the scale inhibition efficiency was 90%, and the microbial sterilization rate was 83%. The circulating water treated with the agent effectively delayed the corrosion of stainless steel pipes. This test example illustrates that a volume ratio of 1:100 represents a relatively small dosage, leading to slightly lower test results.

[0071] Test Example 2

[0072] I. Reaction: Municipal reclaimed water, concentrated three times, was added to the reactor as circulating water. The composite corrosion inhibitor provided in Example 1 was added, with a ratio of composite corrosion inhibitor to circulating water solution of 1:60. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grits of 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. The pieces were then soaked in acetone for 10 minutes to remove grease, and then soaked in anhydrous ethanol for 10 minutes to remove moisture before being placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating plate method, and the reaction was carried out at 200 rpm for 24 hours at a temperature of 20–25°C.

[0073] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve testing; the corrosion inhibition efficiency of the composite agent on stainless steel was determined by Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0074] The volume ratio of the composite corrosion inhibitor provided in Example 1 of this invention to municipal reclaimed water concentrated three times was 1:60. After 24 hours of experiment, the corrosion inhibition efficiency for stainless steel pipes was 76%, the scale inhibition efficiency was 98%, and the microbial sterilization rate was 93%. The circulating water treated with the added agent effectively delayed the corrosion of stainless steel pipes.

[0075] Test Example 3

[0076] I. Reaction: Municipal reclaimed water, concentrated three times, was added to the reactor as circulating water. The composite corrosion inhibitor provided in Example 1 was added, with a ratio of composite corrosion inhibitor to circulating water solution of 1:60. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grits of 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. The pieces were then soaked in acetone for 10 minutes to remove grease, followed by soaking in anhydrous ethanol for 10 minutes to remove moisture, and then placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating plate method, and the reaction was carried out at 200 rpm for 3 days at a temperature of 20–25°C.

[0077] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve analysis. The Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0078] The volume ratio of the composite corrosion inhibitor provided in Example 1 of this invention to municipal reclaimed water concentrated three times was 1:60. After 3 days of experimentation, the corrosion inhibition efficiency for stainless steel pipes was 80%, the scale inhibition efficiency was 99%, and the microbial sterilization rate was 95%. The circulating water treated with the added agent effectively delayed the corrosion of stainless steel pipes.

[0079] Test Example 4

[0080] I. Reaction: Four times concentrated municipal reclaimed water was added to the reactor as circulating water, along with the composite corrosion inhibitor provided in Example 1, wherein the ratio of the composite corrosion inhibitor to the circulating water solution was 1:60. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grits of 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. They were then soaked in acetone for 10 minutes to remove grease, and then soaked in anhydrous ethanol for 10 minutes to remove moisture before being placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating plate method, and the reaction was carried out at 200 rpm for 3 days at a temperature of 20–25°C.

[0081] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve analysis. The Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0082] The composite corrosion inhibitor provided in Example 1 of this invention has a volume ratio of 1:60 with municipal reclaimed water that is 4 times concentrated as circulating water. After 3 days of experimentation, the corrosion inhibition efficiency for stainless steel pipes was 72%, the scale inhibition efficiency was 95%, and the microbial sterilization rate was 90%. The circulating water treated with the added agent effectively delayed the corrosion of stainless steel pipes.

[0083] Test Example 5

[0084] I. Reaction: Municipal reclaimed water, concentrated five times, was added to the reactor as circulating water. The composite corrosion inhibitor provided in Example 1 was added, with a ratio of composite corrosion inhibitor to circulating water solution of 1:60. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grades 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. The pieces were then soaked in acetone for 10 minutes to remove grease, and then soaked in anhydrous ethanol for 10 minutes to remove moisture before being placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating hanging method, and the reaction was carried out at a temperature of 20–25°C and a stirring speed of 200 rpm for 3 days.

[0085] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve analysis. The Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0086] The volume ratio of the composite corrosion inhibitor provided in Example 1 of this invention to municipal reclaimed water concentrated 5 times as circulating water is 1:60. After 3 days of experiment, the corrosion inhibition efficiency of stainless steel pipes is 70%, the scale inhibition efficiency is 95%, and the microbial sterilization rate is 90%. The circulating water treated with the added agent effectively delays the corrosion of stainless steel pipes.

[0087] Test Example 6

[0088] I. Reaction: Municipal reclaimed water, concentrated three times, was added to the reactor as circulating water. The composite corrosion inhibitor provided in Example 1 was added, with a ratio of composite corrosion inhibitor to circulating water solution of 1:60. Stainless steel test pieces were progressively sanded with water-resistant sandpaper at grades 800#, 1200#, and 2000#, followed by polishing with 0.5μm diamond abrasive paste. They were then soaked in acetone for 10 minutes to remove grease, and then soaked in anhydrous ethanol for 10 minutes to remove moisture before being placed in a desiccator. Before use, the stainless steel test pieces were irradiated under a UV lamp for 30 minutes. The dried and sterilized stainless steel test pieces and electrodes were immersed in the circulating water mixture using a rotating plate method, and the reaction was carried out at a temperature of 20–25°C and a stirring speed of 200 rpm for 20 days.

[0089] II. Testing and Analysis: The immersed stainless steel test pieces and electrodes were removed at the aforementioned time intervals. The corrosion inhibition efficiency of the composite agent on stainless steel was determined by weight loss method, electrochemical impedance spectroscopy, and polarization curve analysis. The Ca... 2+ Mg 2+ Alkalinity, Cl - The scale inhibition rate was tested by concentration; the bactericidal rate of the composite agent on the circulating water was obtained by ultraviolet fluorescence and spectrophotometry; the corrosion and scaling tendency of the stainless steel sample surface was determined by XPS, contact angle, AFM, SEM and other methods, so as to obtain whether the composite agent adsorbs and forms a film on the stainless steel sample surface, the film thickness, corrosion morphology and surface chemical composition, etc.

[0090] The composite corrosion inhibitor provided in Example 1 of this invention, mixed with municipal reclaimed water concentrated three times, was used as circulating water at a volume ratio of 1:60. After 20 days of experimentation, the corrosion inhibition efficiency for stainless steel pipes was found to be 82%. Since the effective scale inhibition time and effective bactericidal time of the bactericide in the circulating water are at most one week, the scale inhibition rate and bactericidal rate were not tested in this experiment. The circulating water treated with the added agent effectively delayed the corrosion of stainless steel pipes.

[0091] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. Use of a complex corrosion inhibitor for inhibiting corrosion of stainless steel, characterized in that, The composite corrosion inhibitor is a double quaternary ammonium salt, a hydrolyzed polymaleic anhydride and water; the mass concentration of the double quaternary ammonium salt is 3.0-4.0 g / L, the mass concentration of the hydrolyzed polymaleic anhydride is 1.5 g / L, and the mass ratio of the double quaternary ammonium salt to the hydrolyzed polymaleic anhydride is (2.0-2.7):1; The double quaternary ammonium salt has a structural formula as shown in formula 1: R is C in formula 1 m H 2m+1 , C m H 2m+1 CH2CO2or C m H 2m+1 COOCH2CH2, 8 < m < 13; Y is CH2, NCH3, S or O; The hydrolyzed polymaleic anhydride has a structural formula as shown in formula 2: In formula 2, 8≤m≤13, and 8≤n≤13; The service environment of the stainless steel includes industrial circulating cooling water; The volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is 1:(50-100); The application includes the following steps: The composite corrosion inhibitor is intermittently added into the industrial circulating cooling water, the obtained industrial circulating cooling water containing the composite corrosion inhibitor is circulated in a stainless steel pipeline to perform circulating cooling, and the concentration ratio of the industrial circulating cooling water is 3-5 times.

2. Use according to claim 1, characterized in that, The volume ratio of the composite corrosion inhibitor to the industrial circulating cooling water is 1:(60-95).

3. Use according to claim 1 or 2, characterized in that, The industrial circulating cooling water is reclaimed water, and the water quality indexes of the reclaimed water include: the pH value is 7.55±0.12; the conductivity is 885±12.65 mu s*cm -1 ; the total hardness is 244.5±3.25 mg*L -1 ; the Cl - content is 108.12±2.76 mg*L -1 ; the SO4 2- content is 177.0±3.08 mg*L -1 ; the NO3 - content is 98.55±2.24 mg*L -1 ; the PO4 3- content is 1.24±0.08 mg*L -1 ; the NH4 + content is 4.55±0.22 mg*L -1 ; the COD Cr is 55.7±1.32 mg*L -1 ; the BOD5 content is 45.3±1.85 mg*L -1 ; the turbidity is 1.62±0.11 NTU; the K + content is 29.55±0.83 mg*L -1 ; the Na + content is 87.37±2.33 mg*L -1 ; the Ca 2+ content is 180.94±2.63 mg*L -1 ; the Mg 2+ content is 63.42±1.62 mg*L -1 ; the Fe 3+ content is 0.23±0.02 mg*L -1 ; the Al 3+ content is 0.76±0.17 mg*L -1 ; the Si 2+ is 27.12±0.73 mg*L -1 ; the Mn 2+ content is 0.20±0.04 mg*L -1 ; the Zn 2+ content is 2.84±0.23 mg*L -1 ; the total number of bacteria is 3.43*10 7 ±5.82*10 5 / L -1 .

4. Use according to claim 1, characterized in that, The material of the stainless steel includes SS304, SS316L or SS317L.

5. The use according to claim 1, characterized in that, The intermittent period of the intermittent addition is 10-20 days.

Images