Compounding method and application of borate microbial corrosion inhibitor

Abstract

The invention discloses a compounding method and application of a borate microbial corrosion inhibitor, and belongs to the technical field of metal corrosion protection. The compound borate is used as an environment-friendly microbial corrosion inhibitor and is used for relieving the problem of microbial corrosion in the service process of a metal material. The compound borate is added into an environment capable of causing microbial corrosion, and it is guaranteed that the total mass concentration range of the borate in the environment is larger than or equal to 80 mg / L and smaller than or equal to 140 mg / L. On the premise that the total mass concentration of borate is kept unchanged, compared with other compound types, sodium octaborate (Na2B8O13. 4H2O) and potassium pentaborate (K2B10O16. 8H2O) are compounded according to the ratio of 1: 1-3: 1, growth of an electroactive microorganism Shewanella oneidensis MR-1 can be synchronously and efficiently inhibited, metal corrosion is slowed down, the synergistic effect is highlighted, and the risk of eutrophication is avoided.

Description

Technical Field

[0001] This invention belongs to the field of metal corrosion protection technology, and relates to a compounding method of borate as a microbial corrosion inhibitor and its application. Background Technology

[0002] Microbial corrosion refers to the process by which the surface of materials is corroded and degraded directly or indirectly by the life activities of microorganisms. Statistics show that the economic losses caused by microbial corrosion exceed 2.7 trillion yuan annually. Circulating cooling water systems are widely used in industrial production, heating, and cooling, but due to the recirculation of water, microorganisms easily proliferate, leading to serious problems such as pipeline corrosion and damage to equipment structures. Therefore, inhibiting microbial corrosion of pipelines has become a key aspect of circulating water treatment.

[0003] Currently, microbial corrosion inhibitors have attracted much attention due to their high antibacterial activity, broad-spectrum applicability, and multiple synergistic mechanisms. However, existing inhibitors generally suffer from problems such as easy secondary pollution, insufficient stability, and induction of microbial resistance, making it difficult to achieve green, stable, and efficient control of microbial corrosion in pipes.

[0004] Patent CN 119100500 B describes a microbial corrosion inhibitor containing sodium thiosulfate, surfactants, dimercaptomethane, oxidants, and sodium sulfide, among other ingredients. Patent CN 118177196 A discloses a compound of 2,2-dibromo-3-nitropropamide and rhamnolipid as an environmentally friendly microbial corrosion inhibitor, achieving both antibacterial and corrosion-inhibiting effects, and is environmentally friendly and pollution-free. Patent CN 101244856 B describes a microbial corrosion inhibitor whose active ingredient is a compound of isothiazolinone, tributyltetradecylphosphonium chloride, and octylphenol polyoxyethylene ether, used to control pipeline corrosion caused by drug-resistant bacteria.

[0005] Furthermore, organic microbial corrosion inhibitors still pose the risk of causing eutrophication in water bodies. As an inorganic antibacterial and corrosion inhibitor, borate research has attracted attention. Boric acid is widely used in the medical field as a low-irritant disinfectant, with mild efficacy, suitable for skin and mucous membrane disinfection, wound disinfection, and treatment of infantile eczema. Pentaborate can be used as a corrosion inhibitor, but higher dosages are needed to achieve a certain bactericidal effect. Sodium octaborate tetrahydrate is a commonly used environmentally friendly preservative in wood protection, possessing highly effective antibacterial properties and requiring low dosage, while also being safe, non-toxic, and non-irritating. Although compounding multiple borates may have the potential for synergistic effects and reduced dosage, optimizing the proportions of each component to synergistically inhibit microbial corrosion remains a key issue that urgently needs to be addressed. Summary of the Invention

[0006] Based on the above background, this invention provides a microbial corrosion inhibitor and its formulation method. The inhibitor is based on a borate compound system, which belongs to the inorganic salt class and poses no risk of eutrophication. The application of the compounded borate of this invention as a microbial corrosion inhibitor solves the problem of limited antibacterial and antiseptic effects of single borate preparations, achieving a dual effect of inhibiting microbial proliferation and mitigating corrosion.

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

[0008] The compound borates mentioned involve boric acid (H3BO3) and potassium pentaborate (K2B). 10 O 16 ·8H2O) and sodium octaborate (Na2B8O) 13 One or more of the following: ·4H2O.

[0009] When used, the concentration range of the inhibitor is ≥80 mg / L and ≤140 mg / L.

[0010] The environment that can produce microbial corrosion is preferably the environment in industrial circulating cooling water systems and central air conditioning cooling water systems that cause microbial corrosion of metals.

[0011] The compound borate microbial corrosion inhibitor can inhibit the proliferation of corrosive microorganisms, thereby inhibiting the corrosion of metal material surfaces by microorganisms and reducing the roughness of metal surfaces.

[0012] The metal materials mentioned include, but are not limited to, carbon steel, stainless steel, brass, and titanium alloys.

[0013] A method for detecting the application of compound borate as a microbial corrosion inhibitor includes the following steps:

[0014] Step 1: Preparation of compound borate microbial corrosion inhibitor

[0015] Sodium octaborate and potassium pentaborate were mixed and dissolved to obtain a stock solution of compound borate microbial corrosion inhibitor with a mass concentration of 1.0 g / L. The stock solution was then mixed evenly with sterile LB liquid culture medium at different volume ratios to obtain a diluted solution for later use.

[0016] Step 2: Antibacterial and Corrosion Inhibition

[0017] Electroactive Shewanella was inoculated into a diluted sterile LB medium solution containing compound borate, and a cleaned metal sample was added. The sample was then placed in a constant-temperature suspension shaker for incubation to inhibit the growth of microorganisms and the corrosion of the metal.

[0018] Further, the mass concentration of the diluted compound borate solution mentioned in step 1 is 80-140 mg / L; the compound borate microbial corrosion inhibitor is one of four types: boric acid + potassium pentaborate, boric acid + sodium octaborate, potassium pentaborate + sodium octaborate, and boric acid + potassium pentaborate + sodium octaborate.

[0019] Furthermore, the concentration of the compound borate is preferably 100 mg / L; the compound borate is preferably composed of sodium octaborate and potassium pentaborate as active ingredients, and their mass ratio is between 1:1 and 3:1, including but not limited to ratios of 1:1, 1.5:1, 2:1, 2.5:1 and 3:1.

[0020] Furthermore, the inoculation ratio of electrically active Shewanella to diluted sterile LB medium containing compound borate was 1:100, and the concentration of microbial strains after inoculation was ~10. 5 CFU / mL.

[0021] Furthermore, the cultivation process is carried out at 32–37°C.

[0022] Furthermore, the oscillation frequency of the suspended oscillator is 100–120 rpm.

[0023] Furthermore, the microbial growth inhibition time was 30 hours.

[0024] Furthermore, the metal microbial corrosion time is 7 days.

[0025] In step 2, the blank control group was the control group without the addition of compound borate, and the same metal plates were used. The experimental group was the one with the addition of compound borate solution. After the experimental group and the control group were cultured for 30 hours, the antibacterial rate of the experimental group under the optimal ratio was maintained at 44.7%-52.4% and the corrosion inhibition rate was maintained at 52.4%-57.1% after 7 days of culture.

[0026] Compared with the prior art, the compound borate microbial corrosion inhibitor provided by the present invention has the following beneficial effects:

[0027] A superior synergistic effect was achieved by combining sodium octaborate and potassium pentaborate at a constant total mass concentration. Experiments confirmed that within the optimal ratio range of 1:1 to 3:1, this compound system not only significantly inhibited the proliferation of electroactive Shewanella, increasing the antibacterial rate to over 44.0%, but also effectively mitigated its corrosion of metallic materials, increasing the corrosion inhibition rate to over 52.0%, manifested as a simultaneous decrease in self-corrosion current and surface roughness, demonstrating both antibacterial and anti-corrosion efficacy. Furthermore, this compound agent exhibited stable performance within the optimal ratio range and shows promising application prospects. Attached Figure Description

[0028] Figure 1 The growth inhibition curves of electroactive Shewanella under different compounding processes;

[0029] Figure 2 Dynamic point polarization curves under different compounding processes;

[0030] Figure 3 Atomic force microscopy images of the surface morphology of the corroded pads under different compounding processes;

[0031] Figure 4 The graph shows the antibacterial rate and metal corrosion inhibition rate under different ratios of sodium octaborate and potassium pentaborate. Detailed Implementation

[0032] The following examples utilize various methods to detect the inhibitory effects of compound borate on the growth of electroactive Shewanella and on the corrosion of metallic materials:

[0033] Example 1

[0034] This embodiment investigates the antibacterial properties of different single-component borate dosages on Shewanella.

[0035] The microorganism described in this embodiment is Shewanella oneidensis MR-1: ATCC700550, which was purchased from the China Microbial Culture Collection Center.

[0036] In this embodiment, the culture medium used for microbial culture is Luria-Bertani (LB) liquid medium, with the following components: 10 g / L peptone, 3 g / L beef meal, 5 g / L sodium chloride, pH adjusted to 7.3, and sterilized at 121°C for 15 min before use.

[0037] The purchased Shewanella lyophilized powder was activated for two generations and cultured to the logarithmic growth phase. Then, it was inoculated into sterile LB broth at a 1:100 inoculation ratio, with a controlled gradient of three single-component borate concentrations. The culture was incubated at 37°C for 30 hours. Every 2 hours, 200 μL samples were transferred to 96-well plates and the absorbance (OD) at 600 nm was measured using an Infinite M200, Tecan, Switzerland microplate reader. 600 The corresponding bacterial growth curves were plotted. A control group without added drugs was also set up. Each experiment was repeated three times.

[0038]

[0039] Among them, OD 600 The absorbance value of bacteria after 30 hours of culture without the addition of borate reagent, OD′ 600 The absorbance value is the value after 30 hours of culture with added borate agent.

[0040] Specifically, boric acid was accurately weighed to achieve concentrations of 40, 60, 80, 100, 120, and 140 mg / L in sterile LB liquid medium.

[0041] Specifically, potassium pentaborate was accurately weighed to achieve a concentration of 40, 60, 80, 100, 120, or 140 mg / L in sterile LB liquid medium.

[0042] Specifically, the sodium octaborate was accurately weighed to achieve a concentration of 40, 60, 80, 100, 120, and 140 mg / L in sterile LB liquid medium.

[0043] The experimental results are shown in Table 1. When the boric acid concentration was maintained in the range of 80–140 mg / L, the antibacterial rate remained between 15.8% and 23.4%; when the potassium pentaborate concentration was maintained in the range of 100–140 mg / L, the antibacterial rate remained between 21.4% and 25.0%; and when the sodium octaborate concentration was maintained in the range of 80–140 mg / L, the antibacterial rate remained between 40.4% and 55.1%. Therefore, when borate is present alone, the antibacterial rate can remain stable when the concentration is maintained in the range of 80–100 mg / L.

[0044] Table 1. Antibacterial rate (%) of different concentrations of borate

[0045]

[0046] Example 2

[0047] This embodiment examines the inhibitory effect of borate compound formulations on microbial growth and on metal corrosion.

[0048] The microorganism described in this embodiment is electroactive Shewanella oneidensis MR-1: ATCC700550;

[0049] In this embodiment, the microbial culture was carried out using Luria-Bertani (LB) liquid medium;

[0050] The corrosion material used in this embodiment is a 20# carbon steel sample, and the carbon steel hanging plate has the following dimensions: length 20mm, width 13mm, and thickness 2mm.

[0051] In this embodiment, an enzyme-linked immunosorbent assay (ELISA) reader was used to detect the absorbance value at 600 nm and calculate the antibacterial rate. For specific operation, please refer to Example 1.

[0052] In this embodiment, an electrochemical workstation (Autolab PGSTAT302N, Metrohm, Switzerland) and an atomic force microscope (Bruker Dimension Icon, Germany) were used to characterize the corrosion electrochemical parameters and corrosion morphology of the metal material surface;

[0053] The specific steps are as follows:

[0054] 1. Antibacterial test

[0055] Based on the results of Example 1, under the condition of keeping the total borate concentration (100 mg / L) constant, seven different culture media were prepared by changing the mass ratio of borate components for antibacterial experiments, namely 100% boric acid (100 mg / L), 100% potassium pentaborate (100 mg / L), 100% sodium octaborate (100 mg / L), and boric acid:potassium pentaborate = 1:1 (50 mg / L boric acid:potassium pentaborate = 1:1). Boric acid:sodium pentaborate = 1:1 (50 mg / L boric acid, 50 mg / L sodium pentaborate), boric acid:sodium pentaborate = 1:1 (50 mg / L potassium pentaborate, 50 mg / L sodium pentaborate), boric acid:sodium pentaborate:sodium pentaborate = 1:1:1 (33.3 mg / L boric acid, 33.3 mg / L potassium pentaborate, 33.4 mg / L sodium pentaborate). A control group without added reagents was also set up. Each sample was tested three times.

[0056] Experimental results are as follows Figure 1 As shown in Table 2, the antibacterial effects of the four compound borates differed from those of the single-component borates. The compound borate with potassium pentaborate was more effective than either of the two single components, while the compound borate with sodium octaborate was less effective than the single component sodium octaborate. The compound borate with potassium pentaborate and sodium octaborate, as well as the compound borate with potassium pentaborate and sodium octaborate, were all more effective than the single components.

[0057] Table 2. Antibacterial rate (%) under different compounding processes

[0058]

[0059] 2. Electrochemical Analysis

[0060] After grinding and cleaning, carbon steel plates were placed in a culture medium containing seven different compound borates, inoculated with Shewanella bacteria, and cultured for 7 days. A control group without added chemicals was also included. The plates were then used as electrodes for electrochemical testing using a three-electrode system. The dynamic potential polarization curves of the carbon steel plates in different compound borate systems were measured using an electrochemical workstation to obtain the self-corrosion current density (i...). corr The corrosion inhibition rate (%) was calculated. The experiment was repeated three times for each sample.

[0061]

[0062] Among them, i corr The self-corrosion current density (μA·cm) of carbon steel electrodes without the addition of compound borate. -2 ), i′ corr The self-corrosion current density (μA·cm) of carbon steel electrodes when compound borate is added. -2 );

[0063] Experimental results are as follows Figure 2 As shown in Table 3, the corrosion inhibition rate was calculated based on the self-corrosion current. The inhibition effect of the potassium pentaborate and sodium octaborate compound process on microbial corrosion was significantly better than that of single components and other compound methods.

[0064] Table 3 Self-corrosion current values ​​(μA·cm) under different compounding processes -2 () and corrosion inhibition rate (%)

[0065]

[0066]

[0067] 3. Atomic force microscopy analysis

[0068] The surface morphology and roughness (root mean square deviation of profile, Rq) of the tablets after microbial corrosion in seven compound systems were presented using atomic force microscopy, while a control group without added drugs was set up.

[0069] Experimental results are as follows Figure 3 As shown in Table 4, after 7 days of microbial corrosion, the surface roughness of the control group was 145 nm. Only the boric acid and sodium octaborate compound group and the potassium pentaborate and sodium octaborate compound group had lower surface roughness than the single component and other compound types, indicating that these two compound types are beneficial to inhibiting the microbial corrosion of carbon steel pads.

[0070] Table 4. Surface roughness Rq (nm) of the coated tablets under different compounding processes.

[0071]

[0072] Example 3

[0073] Based on the results of Example 2, this embodiment preferably uses a combination of sodium octaborate and potassium pentaborate to investigate the inhibitory effects of different ratios of the two borates (0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1) on microbial growth and metal corrosion.

[0074] The microorganism described in this embodiment is Shewanella oneidensis MR-1: ATCC700550;

[0075] In this embodiment, the culture medium used for microbial culture is Luria-Bertani (LB) liquid medium;

[0076] The corrosion material used in this embodiment is a 20# carbon steel sample. The dimensions of the carbon steel hanging plate sample are: 20mm in length, 13mm in width, and 2mm in thickness.

[0077] In this embodiment, an enzyme-linked immunosorbent assay (ELISA) reader was used to detect the absorbance value at 600 nm and calculate the antibacterial rate. For specific operation, please refer to Example 1.

[0078] In this embodiment, an electrochemical workstation is used to characterize the corrosion electrochemical parameters and calculate the corrosion inhibition rate. For specific operation, please refer to Example 2.

[0079] The specific procedures for the antibacterial test and the metal corrosion inhibition test are as follows:

[0080] Based on the results of Example 2, under the condition of a fixed total borate concentration (100 mg / L), sterile LB liquid culture media containing different borate ratios were prepared for antibacterial and corrosion inhibition experiments by changing the mass ratio of sodium octaborate to potassium pentaborate. The ratios were: 0.5:1 (33.4 mg / L sodium octaborate, 66.6 mg / L potassium pentaborate), 1:1 (50 mg / L sodium octaborate, 50 mg / L potassium pentaborate), 1.5:1 (60 mg / L sodium octaborate, 40 mg / L potassium pentaborate), 2:1 (66.6 mg / L sodium octaborate, 33.4 mg / L potassium pentaborate), 2.5:1 (71.4 mg / L sodium octaborate, 28.6 mg / L potassium pentaborate), and 3:1 (75 mg / L sodium octaborate, 25 mg / L potassium pentaborate). A control group without added borate was also included. Each sample was tested three times. OD values ​​were measured. 600 The antibacterial rate and corrosion inhibition rate were calculated based on the self-corrosion current.

[0081] Experimental results are as follows Figure 4 As shown, compared with the 0.5:1 ratio, the sodium octaborate / potassium pentaborate compound agents with a ratio of 1:1 to 3:1 showed better performance in both antibacterial rate and corrosion inhibition rate.

Claims

1. Use of a complex borate salt as an environmentally friendly microbial corrosion inhibitor, characterized in that, The inhibitor is compounded from sodium octaborate (Na2B8O 13 ·4H2O) and potassium pentaborate (K2B 10 O 16 ·8H2O) for use in inhibiting microbial proliferation and corrosion of metal materials in environments that can cause microbial corrosion.

2. The use of the complex borate salt according to claim 1 as an environmentally friendly microbial corrosion inhibitor, characterized in that, The effective concentration of the borate in the environment capable of causing microbial corrosion ranges from ≥80 mg / L to ≤140 mg / L.

3. The use of the complex borate salt according to claim 1 as an environmentally friendly microbial corrosion inhibitor, characterized in that, The complex borate microbial corrosion inhibitor has a ratio of sodium octaborate (Na2B8O 13 ·4H2O) to potassium pentaborate (K2B 10 O 16 ·8H2O) in a range of 1:1 to 3:

1.

4. Use of the complex borate salt according to any one of claims 1 to 2 as an environmentally friendly microbial corrosion inhibitor, characterized in that The environment capable of causing microbial corrosion is an industrial circulating cooling water system or a central air conditioning cooling water system.

5. The use of the complex borate salt according to claim 1 as an environmentally friendly microbial corrosion inhibitor, characterized in that, The metal material includes but is not limited to carbon steel, stainless steel, brass or titanium alloy.

6. The use of the complex borate salt according to claim 1 as an environmentally friendly microbial corrosion inhibitor, characterized in that, The complex borate microbial corrosion inhibitor can reduce the metal self-corrosion current in the microbial corrosion environment, inhibit the corrosion of the metal by the microorganism, and reduce the surface roughness of the metal material.

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