A metal self-propagating boronizing method

Abstract

The present invention provides a self-propagating boronization method for metals and its application in metal corrosion inhibition, which has the characteristics of long-term effectiveness and low cost. The metal surface is pre-treated by silanization by utilizing the controllable continuous hydrolysis and polymerization characteristics of silicate in alkaline aqueous solution; then the active silanol groups formed after the hydrolysis of the silane coupling agent react with the silane layer to form corresponding silanol condensates, thereby grafting amino groups on the metal surface. The amino-functionalized metal can be self-propagated boronized at 20-100°C to form a borated corrosion inhibition layer. In addition, when borates are present in a corrosive environment, continuous boronization can promptly repair cracks in the borated corrosion inhibition layer. Therefore, the corrosion inhibition layer formed by the boronization method provided by the present invention has an exogenous self-repairing effect.

Description

Technical Field

[0001] The invention belongs to the technical field of metal surface treatment, and relates to a metal self-propagating boronizing method and its application in metal corrosion inhibition. Background Art

[0002] A large number of corrosive ions exist in highly concentrated circulating water systems. Metals undergo chemical or electrochemical multiphase reactions with corrosive ions, transforming them into oxidized and ionic states, which reduces the strength and thermal conductivity of the metal material. Adding corrosion inhibitors to circulating water systems is an effective way to reduce the corrosion rate. Organic corrosion inhibitors such as morpholine derivatives, imidazole derivatives, or ketoconazoles require a long time to react with metal surface cations to form a corrosion-inhibiting passivation layer. Metal salt corrosion inhibitors such as zinc chromate or strontium chromate are effective, but their toxicity is too great to be accepted by the environment. Polymeric corrosion inhibitors such as polyphosphates or polycarboxylates will slowly leach out, ultimately leading to the complete failure of the anti-corrosion barrier.

[0003] The hysteresis of the corrosion inhibitor's anti-corrosion effect can be overcome by metal surface treatment processes such as chemical heat treatment. When a metal substrate is placed in a specific medium and heated and insulated, the active atoms in the medium can penetrate into the surface of the workpiece, thereby changing the chemical composition and structure of the workpiece surface. Boriding is an effective surface chemical heat treatment process because the boronized layer generally has excellent properties such as relatively high wear resistance, high fatigue strength, good corrosion resistance, red hardness, high-temperature oxidation resistance, and heat resistance. CN 114703447A discloses a boronizing agent with a single-phase Fe2B structure. Its main raw materials are borax and boron carbide. The metal is boronized by keeping the temperature at 900-1050°C for 4-7 hours. CN 114774841B discloses a method for boronizing the surface of a cemented carbide. In order to reduce the temperature of the boronizing treatment, the metal surface is subjected to a series of treatments such as hydroxylation enrichment. The metal surface can be boronized by keeping the temperature at 850-950°C for 4-7 hours. However, high temperature is still a necessary condition for the boronizing process.

[0004] In addition, although boronizing treatment of metal surfaces can show good corrosion inhibition effect, in a corrosive environment, if the micron-scale boronized layer is broken and cannot be repaired immediately, the overall anti-corrosion barrier will face the risk of failure.

[0005] Therefore, effectiveness, long-term effectiveness and low cost of corrosion protection remain the goals of metal surface treatment processes. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention provides a self-propagating boronization method and its application in metal corrosion inhibition. By pre-treating the metal substrate with surface silanization and amination, self-propagating boronization can be achieved at a relatively low temperature, forming a boride layer in a relatively short time, thereby achieving metal corrosion inhibition.

[0007] According to one aspect of the present invention, a metal self-propagating boronization method is provided, which is characterized by comprising performing surface silanization pretreatment on a metal substrate, performing amino-functionalization pretreatment on the silanized metal, and performing self-propagating boronization treatment on the amino-functionalized metal substrate.

[0008] The metal substrate is subjected to surface silanization pretreatment, which includes the following steps: polishing the metal to remove the surface oxide layer, preparing a silicate solution by weighing silicate, ethanol, and water in a volume ratio of 1-5:25-75:1-2; adjusting the solution pH to between 11 and 13, and then purging with nitrogen for 10 minutes to remove dissolved oxygen. The solution is then transferred to a reactor, and the metal substrate is placed in the solution. The reaction is sealed and subjected to static hydrolysis at 20-100°C for 6 hours to obtain a surface-silanized metal substrate.

[0009] The amino-functionalized pretreatment of the silanized metal includes the following steps: preparing a silane coupling agent solution by weighing a silane coupling agent, ethanol, and water in a volume ratio of 1-5:53-93:1-2; adjusting the solution pH to between 2 and 5, and then purging with nitrogen for 10 minutes to remove dissolved oxygen. The solution is then transferred to a reactor, and the silanized metal substrate is placed in the solution. The reactor is sealed and subjected to static condensation at 20-100°C for 6 hours to obtain a surface-amino-functionalized metal substrate.

[0010] The self-propagating boronization treatment of the amino-functionalized metal substrate includes the following steps: preparing a saturated borate solution with deionized water, immersing the carbon steel sample pre-treated with amino-functionalization in the solution and sealing it, and maintaining it at 20-100°C for 1-10 days to achieve the metal self-propagating boronization treatment.

[0011] According to one aspect of the present invention, an application in metal corrosion inhibition is provided, characterized in that metal devices with corrosion risks in a circulating water system are treated with self-propagating boronization, and the boride layer provides an effective corrosion barrier; in addition, borates are added to the circulating water so that the boride layer on the surface of the metal device can achieve a self-repair effect after rupture, thereby achieving long-term corrosion protection.

[0012] The present invention has the following beneficial effects:

[0013] The present invention provides a self-propagating boronization method and its application in metal corrosion inhibition. The controlled continuous hydrolysis and polymerization properties of silicates in alkaline aqueous solutions are utilized to perform a silanization pretreatment on carbon steel. The active silanol groups formed by hydrolysis of a silane coupling agent containing amino groups react with the silicon oxide layer on the metal surface to form corresponding silanol condensates, thereby completing amino-functionalized pretreatment on the metal surface. The amino groups grafted onto the metal substrate surface enhance the non-covalent interaction with the borate. The borate is anchored to the metal substrate surface, and the metal surface is then boronized through an interfacial self-diffusion process, thereby coupling the boron element with the outer electrons of the metal element to prevent the metal from becoming ionic and oxidized. In the present invention, amino-functionalization of the carbon steel surface is achieved through a simple silanol condensation reaction. The pretreated carbon steel then enriches the borate through hydrogen bonding and chemical adsorption, allowing the metal surface to be boronized at temperatures between 20°C and 100°C. The self-propagating boronization corrosion inhibition mode is particularly suitable for borate-rich circulating water systems. During the operation of the system, continuous boronizing can repair the cracks in the corrosion inhibition layer in time, so that the borided layer exhibits an exogenous self-repairing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The electrochemical impedance spectra of the carbon steel samples in Example 1, Example 2 and Example 3 are shown;

[0015] Figure 2 The potentiodynamic polarization curves of the carbon steel samples in Example 1, Example 2 and Example 3 are shown;

[0016] Figure 3 The corrosion rates and corrosion protection rates of the carbon steel samples in Example 1, Example 2, and Example 3 are shown. DETAILED DESCRIPTION

[0017] The following are some exemplary embodiments, which describe the materials and application environments described in the present invention in detail so that technicians can understand them more clearly. However, the following examples and descriptions are not limiting conditions of the present invention. Within the technical background described in the present invention, different environmental scenarios, different improved solutions or other equivalent replacements can be implemented, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be based on the appended claims.

[0018] Example 1

[0019] Self-propagating boronizing method using boric acid to provide active boron:

[0020] A Q235 carbon steel sheet measuring 30 mm long, 20 mm wide, and 2 mm thick was selected as the experimental sample. The carbon steel was polished with 600-, 1200-, and 2000-grit sandpaper to remove the surface oxide layer. 5 mL of tetraethyl orthosilicate and 75 mL of ethanol were mixed thoroughly. The pH of the solution was adjusted to 13 with aqueous ammonia. 1 mL of deionized water was added, and the mixture was purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor, and the carbon steel sample was completely immersed in the solution. The reactor was sealed and statically hydrolyzed at 60°C for 6 hours. The silanized carbon steel was then cleaned and dried. 5 mL of 3-aminopropyltriethoxysilane and 93 mL of ethanol were mixed thoroughly, and the pH of the solution was adjusted to 3 with acetic acid. 1 mL of deionized water was added, and the mixture was purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor. A silanized carbon steel sample was then completely immersed in the solution, sealed, and subjected to static hydrolysis at 60°C for 6 hours. The amino-functionalized carbon steel was then cleaned and dried to obtain the amino-functionalized carbon steel. A saturated boric acid solution was prepared, and the amino-functionalized carbon steel sample was immersed in the solution, sealed, and maintained at 60°C for 3 days to complete the self-propagating boronization treatment. A control sample was polished and left untreated.

[0021] Electrochemical corrosion performance test:

[0022] The carbon steel sample to be measured was used as the working electrode, and a Pt electrode with the same surface area was selected as the counter electrode, and a saturated calomel electrode was used as the reference electrode. Electrochemical tests were performed using a Multi Autolab electrochemical workstation (Metrohm, Switzerland) and a three-electrode system. The electrolyte was 60 mM sodium chloride solution. Electrochemical impedance spectroscopy and potentiodynamic polarization curve tests were performed in this system. The potentiodynamic polarization curve was measured at a scan rate of 0.005 V / s in the potential range of -1.0 V to +0.9 V for OCP. Equivalent circuit fitting and parameter calculations (such as corrosion rate, etc.) were performed by Nova 2.1 software.

[0023] Simulated circulating water system corrosion inhibition performance test:

[0024] A simulated circulating water system was designed with a water storage capacity of 5 L and a circulation rate of 6 L / h. The heat exchange tubes were 150 mm long, 4 mm inner diameter, and 1 mm thick. The surfaces contacting the hot fluid were chrome-plated. The cold fluid flowed through the tube side, with circulating water as the cold medium and an inlet / outlet temperature difference of 8-12°C. The hot fluid flowed through the shell side, with deionized water as the hot medium and an inlet / outlet temperature of 80±2°C. The system operated for a 7-day period, during which 4 mM sodium chloride and 18 mM boric acid solutions were used as makeup water. The corrosion rate of the heat exchange tubes was determined by weight loss, and the average corrosion rate during system operation was calculated. The control group did not contain borate.

[0025] Test results:

[0026] 1. Electrochemical corrosion test results:

[0027] Table 1-1 Electrochemical corrosion test results of the control group

[0028]

[0029] Table 1-2 Electrochemical corrosion test results of the test group described in Example 1

[0030]

[0031] The results show that compared with the control group, the self-corrosion potential and self-corrosion current of carbon steel after self-propagating boronization are closer to 0, indicating that the boronization treatment makes carbon steel less susceptible to corrosion; the electrochemical impedance increases by 3.62 times, and the corrosion protection rate reaches 75.7%.

[0032] 2. Test results of corrosion inhibition performance of simulated circulating water system:

[0033] The initial mass of the heat exchange tube in the control group was 25.71g, and the mass was reduced to 25.25g after 7 days of operation in the simulated circulating water system; the initial mass of the heat exchange tube treated with self-propagating boronization was 25.97g, and the mass was reduced to 25.87g after 7 days of operation in the simulated circulating water system. Compared with the control group, the anti-corrosion efficiency reached 78.3%.

[0034] Example 2

[0035] Sodium tetraborate provides active boron in self-propagating boronization method:

[0036] The pretreatment method of the test sample is the same as that of Example 1. 5 mL of tetrabutyl orthosilicate and 75 mL of ethanol were mixed thoroughly. The pH of the solution was adjusted to 13 with aqueous ammonia. 1 mL of deionized water was added and then purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor, and the carbon steel sample was completely immersed in the solution. After sealing, the solution was statically hydrolyzed at 90°C for 3 hours. After washing and drying, the silanized carbon steel was obtained. 5 mL of 3-aminopropyltrimethoxysilane and 93 mL of ethanol were mixed thoroughly. The pH of the solution was adjusted to 4 with acetic acid. 1 mL of deionized water was added and then purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor, and the silanized carbon steel sample was completely immersed in the solution. After sealing, the solution was statically hydrolyzed at 90°C for 3 hours. After washing and drying, the amino-functionalized carbon steel was obtained. A saturated sodium tetraborate solution was prepared, and the amino-functionalized carbon steel sample was immersed in the solution and sealed, and maintained at 90°C for 3 days to complete the metal self-propagating boronizing treatment.

[0037] Electrochemical corrosion performance test:

[0038] The testing method is the same as that in Example 1.

[0039] Simulated circulating water system corrosion inhibition performance test:

[0040] During the operation, 4 mM sodium chloride and 4.5 mM sodium tetraborate solution were used as supplementary water, and the remaining steps were the same as those in Example 1.

[0041] Test results:

[0042] 1. Electrochemical corrosion test results:

[0043] The results of the control group were the same as those in Example 1.

[0044] Table 2-1 Electrochemical corrosion test results of the test group described in Example 2

[0045]

[0046] The results showed that the electrochemical impedance of carbon steel increased by 12.68 times and the corrosion protection rate reached 93.6% when sodium tetraborate was used as the boronizing agent.

[0047] 2. Test results of corrosion inhibition performance of simulated circulating water system:

[0048] The results of the control group were the same as those of Example 1. The initial mass of the heat exchange tube treated with self-propagating boronization was 25.93 g. After 7 days of operation in the simulated circulating water system, the mass was reduced to 25.90 g, and the anti-corrosion efficiency reached 93.5% compared with the control group.

[0049] Example 3

[0050] Sodium pentaborate provides active boron in self-propagating boronization method:

[0051] The pretreatment of the test samples was the same as in Example 1. 10 mL of tetrabutyl orthosilicate and 75 mL of ethanol were mixed thoroughly. The pH of the solution was adjusted to 11 with aqueous ammonia. 1 mL of deionized water was added, and the mixture was purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor, and the carbon steel sample was completely immersed in the solution. The mixture was sealed with a lid and subjected to static hydrolysis at 100°C for 1 hour. The silanized carbon steel was then washed and dried to obtain the silanized carbon steel. 10 mL of 3-aminopropyltriethoxysilane and 93 mL of ethanol were mixed thoroughly. The pH of the solution was adjusted to 3 with acetic acid. 1 mL of deionized water was added, and the mixture was purged with argon for 10 minutes to remove dissolved oxygen. The solution was transferred to a polytetrafluoroethylene-lined reactor, and the silanized carbon steel sample was completely immersed in the solution. The mixture was sealed with a lid and subjected to static hydrolysis at 100°C for 1 hour. The amino-functionalized carbon steel was then washed and dried to obtain the amino-functionalized carbon steel. A saturated pentaborate solution was prepared, and the amino-functionalized carbon steel sample was immersed in the solution and sealed, and maintained at 100°C for 3 days to complete the metal self-propagating boronizing treatment.

[0052] Electrochemical corrosion performance test:

[0053] The testing method is the same as that in Example 1.

[0054] Simulated circulating water system corrosion inhibition performance test:

[0055] During the operation, 4 mM sodium chloride and 3.6 mM sodium pentaborate solution were used as supplementary water, and the remaining steps were the same as those in Example 1.

[0056] Test results:

[0057] 1. Electrochemical corrosion test results:

[0058] The results of the control group were the same as those in Example 1.

[0059] Table 3-1 Electrochemical corrosion test results of the test group described in Example 3

[0060]

[0061] The results showed that using sodium pentaborate as the boronizing agent, the electrochemical impedance of carbon steel increased by 17.11 times and the corrosion protection rate reached 93.9%.

[0062] 2. Test results of corrosion inhibition performance of simulated circulating water system:

[0063] The results of the control group were the same as those of Example 1. The initial mass of the heat exchange tube treated with self-propagating boronization was 25.89 g, and after 7 days of operation in the simulated circulating water system, the mass was reduced to 25.85 g, and the anti-corrosion efficiency reached 91.3% compared with the control group.

[0064] The above are only some embodiments of the present invention, but the scope of protection of the present invention is not limited to the above cases. Formula improvements or equivalent replacements under the background of this technology should fall within the scope of the present invention.

Claims

1. A self-propagating boronizing method, characterized in that: The method includes: The metal substrate is subjected to surface silanization pretreatment, whereby silicate undergoes hydrolysis and condensation reaction on the surface of the metal substrate to form a silane layer on the metal surface; The silanized metal is pre-treated with amino functionalization, whereby the amino-containing silane coupling agent undergoes a hydrolysis-condensation reaction on the surface of the silane layer, grafting amino groups on the metal surface to form an amino-functionalized metal substrate; The amino-functionalized metal substrate is subjected to self-propagating boronization treatment, wherein the amino-functionalized metal substrate is immersed in a saturated borate solution, sealed in a nitrogen atmosphere at a temperature of 20-100° C. for 1-10 days, and self-propagating boronization is performed on the metal surface to form a boronized layer.

2. The self-propagating boronizing method according to claim 1, characterized in that: When the silicate undergoes hydrolysis and condensation reaction on the surface of the metal substrate, the pH value of the system is between 11 and 13.

3. The self-propagating boronizing method according to claim 1, characterized in that: When the silane coupling agent undergoes a hydrolysis condensation reaction on the surface of the silane layer, the pH value of the system is between 2 and 5.

4. The self-propagating boronizing method according to claim 1, characterized in that: When the metal substrate is immersed in the saturated borate solution, the pH value of the system is between 6 and 8.

5. The self-propagating boronizing method according to claim 1, characterized in that: The silicate comprises at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.

6. The self-propagating boronizing method according to claim 1, characterized in that: The amino-containing silane coupling agent includes at least one of γ-aminopropyltriethoxysilane and γ-aminopropyltrimethoxysilane.

7. The self-propagating boronizing method according to claim 1, characterized in that: The borate includes at least one of sodium tetraborate, potassium tetraborate, sodium pentaborate and potassium pentaborate.

8. The self-propagating boronizing method according to claim 1, characterized in that: The silicate undergoes hydrolysis and condensation reaction in a nitrogen atmosphere at a temperature of 30-60°C.

9. The self-propagating boronizing method according to claim 1, characterized in that: The amino-containing silane coupling agent undergoes a hydrolysis-condensation reaction at a temperature of 30-60° C. under a nitrogen atmosphere.

10. Application of the self-propagating boronizing method according to claim 1 in metal corrosion inhibition in a circulating water system.

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