A leveling agent for column hot galvanizing and a preparation method thereof

Abstract

This invention discloses a leveling agent for hot-dip galvanizing of columns and its preparation method, belonging to the field of galvanizing technology. The method involves weighing, by weight, a polyamine pyridine quaternary ammonium salt, 1,3-propanediaminetetraacetic acid (PPTA), a leveling agent, isomeric tridecyl alcohol polyoxyethylene ether (ITO), disodium ethylenediaminetetraacetate (EDTA), and deionized water. The deionized water is heated, and ITO and EDTA are added sequentially, stirring to obtain a composite solvent. The polyamine pyridine quaternary ammonium salt is then added, and stirring continues. 1,3-PPTA is added and stirred, and the leveling agent is added in 3-5 portions. After cooling, the leveling agent for hot-dip galvanizing of columns is obtained. The leveling agent prepared by this invention can significantly improve the surface forming quality of the galvanized coating. The surface roughness Ra value of the coating obtained after applying this leveling agent is between 0.15 and 0.18 μm, resulting in a smooth and flat surface, effectively improving the surface quality of hot-dip galvanized columns.

Description

Technical Field

[0001] This invention relates to the field of galvanizing technology, specifically to a leveling agent for hot-dip galvanizing of columns and its preparation method. Background Technology

[0002] Hot-dip galvanizing, as one of the core processes for metal corrosion protection, is widely used in the surface treatment of metal components such as columns. Leveraging the physical shielding and electrochemical sacrificial protection of the zinc layer, it effectively extends the service life of columns in outdoor and industrial corrosive environments, making it a crucial step in the processing of column components in roads, buildings, and power industries. Leveling agents, as important additives in the hot-dip galvanizing process, directly determine the deposition state of the zinc layer on the column substrate surface. They not only affect the surface smoothness, gloss, and other appearance and physical properties of the coating, but are also closely related to the coating density and thickness uniformity.

[0003] Current traditional hot-dip galvanizing processes and conventional leveling agents result in high surface roughness and poor consistency of the coating, which easily leads to problems such as zinc nodules, runs, unevenness, etc. The zinc liquid is deposited and distributed unevenly on the substrate surface, resulting in large dispersion in coating thickness. Locally thin areas are prone to corrosion weak points, while excessively thick areas are prone to brittleness and peeling. The overall density and structural stability of the coating are insufficient.

[0004] In addition, under the corrosive effects of salt spray and complex media, the coating is prone to early pitting, white rust and red rust. The corrosion develops rapidly and spreads over a wide area, resulting in the exposure of the substrate and peeling of the coating in a short period of time. The protection period is short and the durability is insufficient.

[0005] Based on this, the present invention designs a leveling agent for hot-dip galvanizing of columns and its preparation method to solve the above problems. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing a leveling agent for hot-dip galvanizing of columns, comprising the following steps: S1: Weigh out 15-25 parts by weight of polyamine pyridine quaternary ammonium salt, 10-18 parts of 1,3-propanediaminetetraacetic acid, 8-15 parts of plating agent, 5-10 parts of isomeric tridecyl alcohol polyoxyethylene ether, 3-7 parts of disodium ethylenediaminetetraacetate and 35-50 parts of deionized water. The preparation method of the plating agent is as follows: A1. Pump anhydrous ethanol into the reactor, add epichlorohydrin dropwise to the reactor under a nitrogen atmosphere, heat to 45-52℃, then add boron trifluoride diethyl ether complex, and maintain the temperature for reaction; A2. After the reaction is complete, deionized water is pumped in, the pH is adjusted to 7.5-8.2, the mixture is allowed to stand and separate into layers, and the upper organic phase is washed to obtain the precursor. A3. Add 4-aminopyridine and sodium hydroxide to the precursor, and keep the reaction at 65-75℃. After the reaction is completed, cool down to 25-35℃ and dry under vacuum to obtain the intermediate. A4. Add deionized water to the intermediate and stir at 40-50℃ until dissolved. Add ethylenediamine, heat to 75-85℃, maintain the temperature for reaction, cool to room temperature, adjust pH to 6.2-7.8, and vacuum concentrate to obtain the plating agent. S2: Heat deionized water to 52-64℃, add isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt, and continue stirring; S3: Add 1,3-propanediaminetetraacetic acid to S2 and stir. Add the leveling agent in 3-5 portions while stirring. After each addition, raise the temperature. After all the agent has been added, continue stirring and allow it to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0007] Preferably, S2 specifically involves: heating deionized water to 52-64°C, sequentially adding isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate, stirring at 300-500 r / min for 20-30 min to obtain a composite solvent, adding a polyamine pyridine quaternary ammonium salt to the composite solvent, and stirring for 30-40 min.

[0008] Preferably, S3 specifically involves: adding 1,3-propanediaminetetraacetic acid to S2, stirring at 200-300 r / min for 15-20 min, then adding the leveling agent in 3-5 portions while stirring, with an interval of 3-7 min between each addition, raising the temperature by 2-3°C after each addition, and continuing to stir for 25-35 min after all additions are completed, and then naturally cooling to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0009] Preferably, A1 specifically involves: pumping 35-45 parts by weight of anhydrous ethanol into the reactor, adding 18-25 parts of epichlorohydrin dropwise to the reactor under a nitrogen atmosphere, at 25-35°C and 60-100 r / min, raising the temperature to 45-52°C at 2-4°C / min, and then adding 0.05-0.15 parts of boron trifluoride diethyl ether complex and maintaining the temperature for 5-8 hours.

[0010] Preferably, A2 is specifically as follows: after the reaction is completed, 40-50 parts of deionized water are pumped in, and the pH is adjusted to 7.5-8.2 by 0.1M sodium hydroxide aqueous solution. After standing for 30-60 minutes, the phases are separated. The lower aqueous phase is discharged through the bottom discharge port of the reactor, and the upper organic phase is washed with deionized water 2-3 times to obtain the precursor.

[0011] Preferably, A3 specifically comprises: adding 4.5-7.5 parts by weight of 4-aminopyridine and 2.0-3.5 parts by weight of flake sodium hydroxide to the precursor, and reacting at 65-75°C for 8-12 hours. After the reaction is completed, the temperature is lowered to 25-35°C, and the inorganic salt precipitate generated in the reaction is removed by filtering through a bottom filter. The filtrate is returned to the reaction vessel, and ethanol is removed at 55-65°C and a vacuum of -0.08 MPa to obtain the intermediate.

[0012] Preferably, A4 is specifically prepared by: adding deionized water to the intermediate and stirring at 40-50°C until dissolved; adding 3.2-5.6 parts by weight of ethylenediamine; heating to 75-85°C; maintaining the temperature for 6-10 hours; cooling to room temperature; adjusting the pH to 6.2-7.8 with 0.1M hydrochloric acid; and concentrating to 1 / 3 volume at 55-65°C and a vacuum of -0.08MPa to obtain a uniform plating agent.

[0013] Preferably, the polyamine pyridine quaternary ammonium salt is one or more of hexadecylpyridinium chloride and dodecylpyridinium bromide.

[0014] A leveling agent for hot-dip galvanizing of columns prepared according to the method described above.

[0015] Compared with the prior art, the beneficial effects of this invention are as follows: 1. The leveling agent for hot-dip galvanizing columns prepared in this invention can significantly improve the surface forming quality of the galvanized coating. After applying this leveling agent, the surface roughness Ra value of the coating is between 0.15-0.18μm, the surface is smooth and flat, and the surface quality of hot-dip galvanized columns is effectively improved. It can effectively improve the thickness uniformity of the galvanized coating. After application, the standard deviation of the coating thickness sample is only 0.62-0.85μm. The deposition thickness of the coating is uniform in all areas of the substrate surface, which can effectively avoid the occurrence of uneven coating thickness in some areas. This allows the galvanized coating to form a uniform and dense structure, laying a solid foundation for the overall stability of the galvanized column performance, and enabling all parts of the coating to play a stable protective and usable role.

[0016] 2. The leveling agent of this invention has excellent and long-lasting corrosion resistance. After 2000 hours of salt spray corrosion testing, the coating showed no pitting or penetrating corrosion throughout the test, and the coating structure remained intact, with stable corrosion protection. Specifically, there were no visible corrosion changes in the coating after 72 hours, only a small amount of white spots (less than 2%) after 168 hours, and white rust (less than 2%) after 500 hours, with virtually no red rust or coating peeling. The red rust area was less than 4% after 1000 hours and did not exceed 9% after 2000 hours. The corrosion phenomenon appeared late, developed slowly, and was mild, providing long-lasting protection for the substrate and excellent protection effect. This significantly improved the durability of galvanized columns in complex corrosive environments and effectively extended the service life of galvanized columns. Attached Figure Description

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

[0018] Figure 1 This is a graph showing the electrodynamic polarization curves; Figure 2 The infrared spectrum of the uniform plating agent prepared in Example 2 of this invention is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] Example 1: This example provides a method for preparing a leveling agent for hot-dip galvanizing of columns, including the following steps: S1: Weigh out 15 parts by weight of polyamine pyridine quaternary ammonium salt (hexadecylpyridinium chloride), 10 parts of 1,3-propanediaminetetraacetic acid, 8 parts of plating agent, 5 parts of isomeric tridecyl alcohol polyoxyethylene ether, 3 parts of disodium ethylenediaminetetraacetate and 35 parts of deionized water. The preparation method of the plating agent is as follows: A1. By weight, pump 35 parts of anhydrous ethanol into the reactor. Under a nitrogen atmosphere, at 25°C and 60 r / min, add 18 parts of epichlorohydrin dropwise to the reactor (total dropwise addition time 20 min). Increase the temperature to 45°C at 2°C / min, then add 0.05 parts of boron trifluoride diethyl ether complex and maintain the temperature for 5 h (the volatile solvent is recovered through the condenser on the top of the reactor during the reaction). A2. After the reaction is complete, 40 parts of deionized water are pumped in, and the pH is adjusted to 7.5-8.2 with 0.1M sodium hydroxide aqueous solution. After standing for 30 minutes, the phases are separated. The lower aqueous phase is discharged through the bottom discharge port of the reactor, and the upper organic phase is washed twice with deionized water to obtain the precursor. A3. By weight, add 4.5 parts of 4-aminopyridine and 2.0 parts of flake sodium hydroxide to the precursor, keep the reaction at 65°C for 8 hours, cool down to 25°C after the reaction is complete, filter through the bottom filter to remove the inorganic salt precipitate generated in the reaction, return the filtrate to the reaction vessel, remove ethanol at 55°C and vacuum degree -0.08MPa to obtain the intermediate; A4. Add deionized water to the intermediate and stir at 40°C until dissolved. Add 3.2 parts by weight of ethylenediamine, heat to 75°C, keep the reaction at this temperature for 6 hours, cool to room temperature, adjust the pH to 6.2-7.8 with 0.1M hydrochloric acid, and concentrate to 1 / 3 volume at 55°C and a vacuum of -0.08MPa to obtain the plating agent. S2: Heat deionized water to 52°C, add isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir at 300 r / min for 20 min to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt to the composite solvent, and stir for 30 min. S3: Add 1,3-propanediaminetetraacetic acid to S2 and stir at 200 r / min for 15 min. Then add the leveling agent in 3 portions while stirring, with an interval of 3 min between each addition. After each addition, raise the temperature by 2°C. After all the agents have been added, continue stirring for 25 min and allow to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0021] Example 2: This example provides a method for preparing a leveling agent for hot-dip galvanizing of columns, including the following steps: S1: Weigh out 25 parts by weight of polyamine pyridine quaternary ammonium salt (dodecylpyridinium bromide), 18 parts of 1,3-propanediaminetetraacetic acid, 15 parts of plating agent, 10 parts of isomeric tridecyl alcohol polyoxyethylene ether, 7 parts of disodium ethylenediaminetetraacetate and 50 parts of deionized water. The preparation method of the plating agent is as follows: A1. By weight, pump 45 parts of anhydrous ethanol into the reactor, and add 25 parts of epichlorohydrin dropwise to the reactor under a nitrogen atmosphere, at 35°C and 100 r / min (total dropwise addition time 20 min). Increase the temperature to 52°C at 4°C / min, and then add 0.15 parts of boron trifluoride diethyl ether complex. Keep the reaction at this temperature for 8 h (the volatile solvent is recovered through the condenser on the top of the reactor during the reaction). A2. After the reaction is complete, 50 parts of deionized water are pumped in, and the pH is adjusted to 7.5-8.2 with 0.1M sodium hydroxide aqueous solution. After standing for 60 minutes, the phases are separated. The lower aqueous phase is discharged through the bottom discharge port of the reactor, and the upper organic phase is washed three times with deionized water to obtain the precursor. A3. By weight, add 7.5 parts of 4-aminopyridine and 3.5 parts of flake sodium hydroxide to the precursor, keep the reaction at 75°C for 12 hours, cool down to 35°C after the reaction is complete, filter through the bottom filter to remove the inorganic salt precipitate generated in the reaction, return the filtrate to the reaction vessel, remove ethanol at 65°C and vacuum degree -0.08MPa to obtain the intermediate; A4. Add deionized water to the intermediate and stir at 50°C until dissolved. Add 5.6 parts by weight of ethylenediamine, heat to 85°C, keep the reaction at this temperature for 10 hours, cool to room temperature, adjust the pH to 6.2-7.8 with 0.1M hydrochloric acid, and concentrate to 1 / 3 volume at 65°C and a vacuum of -0.08MPa to obtain the uniform plating agent. The prepared uniform plating agent was characterized by infrared spectroscopy, and the results are as follows: Figure 2 As shown, 1590-1620cm -1 The appearance of the C=N stretching vibration peak of the pyridine ring at 1450-1520 cm⁻¹ proves that the pyridine ring functional group of 4-aminopyridine has been successfully introduced into the molecular structure of the plating agent; -1 The appearance of the C=C skeletal vibration peak of the pyridine ring at 750-850 cm⁻¹ further proves that the pyridine ring structure was intact and did not undergo cleavage during the reaction; -1 The appearance of an out-of-plane bending peak of the pyridine ring at 2800-3000 cm⁻¹ is a characteristic fingerprint peak of the pyridine ring, further confirming the stable presence of the pyridine ring in the product. -1 The saturated CH (-CH2-, -CH3) stretching vibration peaks appear at 3200-3400 cm⁻¹, originating from the alkyl chain of epichlorohydrin, the alkyl structure of 4-aminopyridine, and the methylene group of ethylenediamine; -1 The appearance of the NH stretching vibration peak at 1050-1150 cm⁻¹ indicates the presence of the primary amine group of 4-aminopyridine, the amino group of ethylenediamine, and the secondary amine group formed during the reaction, verifying the completion of the grafting of 4-aminopyridine in step A3 and the condensation reaction of ethylenediamine with the intermediate in step A4; -1 The presence of a CN stretching vibration peak (in aliphatic amines and pyridine amines) indicates successful linkage between the nitrogen atom and the carbon chain, forming an amino-carbon chain-pyridine ring framework in the product. (1080-1120 cm⁻¹) -1 The appearance of the COC ether bond stretching vibration peak at 3400 cm⁻¹ is a characteristic product peak of epichlorohydrin under the catalysis of boron trifluoride diethyl ether complex, proving that the epoxy group of epichlorohydrin is completely ring-opened, forming an ether bond structure; -1 The presence of a characteristic peak for hydroxyl (-OH) indicates that the hydroxyl group is a byproduct / terminal hydroxyl group of epichlorohydrin ring opening. The broad peak shape suggests the presence of intermolecular hydrogen bonds in the hydroxyl group, which is consistent with the infrared characteristics of organic oxygen-containing functional groups, further verifying the epoxy ring-opening reaction.

[0022] S2: Heat deionized water to 64°C, add isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir at 500 r / min for 30 min to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt to the composite solvent, and stir for 40 min. S3: Add 1,3-propanediaminetetraacetic acid to S2 and stir at 300 r / min for 20 min. Then add the leveling agent in 5 portions while stirring, with an interval of 7 min between each addition. After each addition, raise the temperature by 3°C. After all the additions are complete, continue stirring for 35 min and allow to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0023] Example 3: This example provides a method for preparing a leveling agent for hot-dip galvanizing of columns, including the following steps: S1: Weigh out 21 parts by weight of polyamine pyridine quaternary ammonium salt (composed of hexadecylpyridinium chloride and dodecylpyridinium bromide in a mass ratio of 1:1), 13 parts of 1,3-propanediaminetetraacetic acid, 12.5 parts of plating agent, 7.5 parts of isomeric tridecyl alcohol polyoxyethylene ether, 5 parts of disodium ethylenediaminetetraacetate and 42 parts of deionized water; The preparation method of the plating agent is as follows: A1. By weight, pump 40 parts of anhydrous ethanol into the reactor. Under a nitrogen atmosphere, at 30°C and 86 r / min, add 22 parts of epichlorohydrin dropwise to the reactor (total dropwise addition time 20 min). Increase the temperature to 48°C at 3°C / min, then add 0.10 parts of boron trifluoride diethyl ether complex and maintain the temperature for 6.5 h (the volatile solvent is recovered through the condenser at the top of the reactor during the reaction). A2. After the reaction is complete, 47 parts of deionized water are pumped in, and the pH is adjusted to 7.5-8.2 with 0.1M sodium hydroxide aqueous solution. After standing for 46 minutes, the phases are separated. The lower aqueous phase is discharged through the bottom discharge port of the reactor, and the upper organic phase is washed twice with deionized water to obtain the precursor. A3. By weight, add 6.2 parts of 4-aminopyridine and 2.8 parts of flake sodium hydroxide to the precursor, keep the reaction at 71°C for 10 h, cool to 28°C after the reaction is complete, filter through the bottom filter to remove the inorganic salt precipitate generated in the reaction, return the filtrate to the reaction vessel, remove ethanol at 62°C and vacuum degree -0.08 MPa to obtain the intermediate; A4. Add deionized water to the intermediate and stir at 46°C until dissolved. Add 4.4 parts by weight of ethylenediamine, heat to 80°C, keep the reaction at this temperature for 8 hours, cool to room temperature, adjust the pH to 6.2-7.8 with 0.1M hydrochloric acid, and concentrate to 1 / 3 volume at 58°C and a vacuum of -0.08MPa to obtain the plating agent. S2: Heat deionized water to 61°C, add isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir at 420 r / min for 22 min to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt to the composite solvent, and stir for 38 min. S3: Add 1,3-propanediaminetetraacetic acid to S2 and stir at 230 r / min for 18 min. Then add the leveling agent in 5 portions while stirring, with an interval of 5 min between each addition. After each addition, raise the temperature by 2°C. After all the additions are complete, continue stirring for 31 min and allow to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0024] Comparative Example 1: The difference between this comparative example and Example 2 is that 4-aminopyridine is not added during the preparation of the plating agent.

[0025] Comparative Example 2: The difference between this comparative example and Example 2 is that the polyamine pyridine quaternary ammonium salt is replaced with an equal mass of dodecyltrimethylammonium chloride.

[0026] Comparative Example 3: The difference between this comparative example and Example 2 is that, in S1, 48 parts by weight of polyamine pyridine quaternary ammonium salt (dodecylpyridinium bromide), 7 parts of 1,3-propanediaminetetraacetic acid, 25 parts of plating agent, 29 parts of isomeric tridecyl alcohol polyoxyethylene ether, 14 parts of disodium ethylenediaminetetraacetate and 5 parts of deionized water were weighed.

[0027] Comparative Example 4: The difference between this comparative example and Example 2 is that, in S3: 1,3-propanediaminetetraacetic acid is added to S2 and stirred at 300 r / min for 20 min. Then, the leveling agent is added all at once, and the temperature is increased by 2°C every 5 min. After 5 temperature increases, the stirring is continued for 35 min. The mixture is then naturally cooled to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

[0028] Preparation example: Preparation of galvanized steel sheet samples; (1) Select Q235B steel plate with specifications of 200×100×4mm; (2) Prepare the main plating solution with the following formula: ZnSO4·7H2O 200g / L, NaH2PO4·2H2O 80g / L, NH4Cl 30g / L, trisodium citrate 15g / L, boric acid 25g / L, and dilute to 1L with deionized water. Adjust the pH of the plating solution to 5.0±0.2 (adjusted with 1mol / L H2SO4 or 1mol / L NaOH solution). Add 0.3% of the leveling agent for hot-dip galvanizing of columns prepared in the embodiments and comparative examples of this invention, stir for 30min, and keep warm in a constant temperature water bath at 25±1℃ for later use. (3) Preparation of pre-zinc plating solution: ZnCl2 220g / L, NH4Cl 80g / L, pH=4.5±0.2; The silane sealing solution was prepared by compounding γ-GPS and KH-560 in a volume ratio of 1:1. (4) Place the Q235B steel plate in the pre-galvanizing solution and use DC electroplating at 25℃ and a current density of 2A / dm³. 2 Electroplating for 10 minutes; after electroplating, rinse the steel plate surface with deionized water for 3 minutes to remove residual pre-plating zinc solution; and dry with hot air at 80°C for 10 minutes. (5) Place the dried Q235B steel plate in the main plating solution and use DC electroplating at 25℃ and a current density of 1.5A / dm³. 2 Electroplating for 30 minutes, with continuous stirring at 200 r / min during the electroplating process. After electroplating is completed, remove the steel plate, rinse with deionized water for 3 minutes, and dry with hot air at 80℃ for 15 minutes. (6) Immerse the Q235B steel plate that has been plated into the silane sealing solution and soak at room temperature for 18 minutes. After sealing, take out the sample and air dry it naturally (room temperature 25℃, relative humidity 60%, drying time 24h) to obtain each galvanized steel plate sample.

[0029] Characterization Example 1: The galvanized steel sheet sample obtained in the above steps was cut into 1×1cm test samples, with a single test surface retained. The other 5 surfaces were uniformly sealed with epoxy resin, and the thickness of the sealing layer was controlled to be 0.5mm to avoid contact between the electrolyte and the non-test surfaces. The sample was left to stand for 24 hours to allow the epoxy resin to fully cure.

[0030] Prepare a 3.5% NaCl electrolyte and select a platinum sheet (1 cm² in area). 2 The sample is used as the counter electrode, and the saturated calomel electrode (SCE) is used as the reference electrode. Together with the prepared sample, they form a three-electrode system. All three electrodes are immersed in 3.5% NaCl electrolyte to ensure that the test surface of the sample is completely submerged. The distance between the three electrodes is 2 cm, with no contact and no air bubbles adhering.

[0031] Set the electrochemical workstation to open-circuit potential test mode, test time 3600s, data acquisition frequency 1Hz, and continuous test at 25℃ until the potential curve tends to stabilize (potential fluctuation range ≤ ±2mV / 300s). Record the stabilized open-circuit potential value as the reference potential for subsequent potentiodynamic polarization curve tests.

[0032] Based on the stable potential obtained from the open-circuit potential test, the test parameters for the potentiodynamic polarization curve were set as follows: the scan rate was 1 mV / s, the scan range was the stable open-circuit potential ±0.5 V, the data acquisition interval was 0.1 mV, and the scan was performed continuously at 25 °C. During the test, the electrolyte was kept undisturbed and there were no temperature fluctuations. After the scan was completed, the complete polarization curve data was exported.

[0033] The Tafel extrapolation method was used to fit and analyze the polarization curve data to determine the self-corrosion potential (Ecorr) and self-corrosion current density (Icorr) of the sample.

[0034] The results are as follows Figure 1 As shown, the potential values ​​corresponding to the extrapolated intersection points of the cathode and anode Tafel segments of the polarization curves can be observed. The self-corrosion potentials of Examples 1, 2, and 3 are significantly higher than those of the comparative examples, and the Ecorr values ​​among the three examples are similar, with the curve positions generally biased towards the positive. Among them, the self-corrosion potential of Comparative Example 1 is the most negative, followed by Comparative Examples 2 and 3. Comparative Example 4 is slightly higher than the previous three but still lower than the examples. This indicates that after treatment with the leveling agent prepared by the optimized formula of the present invention, the thermodynamic corrosion resistance of the zinc plating layer is significantly improved. Operations such as missing key components in the leveling agent, replacing the core leveling active ingredient, deviating from the raw material ratio, and changing the method of adding the leveling agent will all lead to an increase in the initial corrosion tendency of the zinc plating layer. Self-corrosion current density is a dynamic core parameter reflecting the corrosion dissolution rate of a material. The smaller the icorr, the lower the electrochemical dissolution rate of the zinc plating layer in the corrosive medium, and the better the actual corrosion resistance. From the current density coordinates corresponding to the intersection points of the polarization curves, it is clear that the self-corrosion current densities of Examples 1, 2, and 3 are significantly lower than all comparative examples. The curve intersection points are all in a lower current density range, and the icorr values ​​within the example groups are extremely small, indicating that the dissolution rate of their zinc plating layers is at an extremely low level. Among the comparative examples, Comparative Example 1 has the largest icorr, indicating the fastest corrosion dissolution rate, followed by Comparative Examples 2 and 3. Although Comparative Example 4 has a slightly lower icorr, it is still much higher than the example groups. Combining the quantitative law of Tafel extrapolation, icorr is positively correlated with the actual corrosion rate of the coating. The extremely low icorr in the example groups means that the corrosion rate of their zinc plating layers in the 3.5% NaCl medium is significantly reduced. In contrast, the comparative examples, due to deviations in the leveling agent formulation / process from the design of this invention, have increased electrochemical reactivity of the zinc plating layer, resulting in a significantly faster dissolution rate.

[0035] Experimental Example 1: The surface hardness (H) of the coating of each galvanized steel sheet sample was tested according to GB / T 6739-2022 "Determination of Hardness of Paint and Varnish by Pencil Method".

[0036] Experimental Example 2: The surface roughness (Ra) of the coating of each galvanized steel plate sample was tested according to GB / T 1031-2009 "Geometric Specifications for Products (GPS) - Surface Roughness Parameters and Their Values ​​by Surface Structure Profile Method".

[0037] Experimental Example 3: The coating thickness (μm) at any 5 points on each galvanized steel sheet sample was measured according to GB / T 4955-2005 "Metallic Coatings - Coating Thickness Measurement - Anodic Dissolution Coulometric Method". The thicknesses were recorded as follows: , , , , First, calculate the arithmetic mean of the five thickness values, and then calculate the sample standard deviation based on the mean. in, For sample standard deviation, This is the arithmetic mean of the coating thickness at five detection points.

[0038] The results are shown in Table 1; Table 1: As shown in the table above, the leveling agent for hot-dip galvanizing of columns prepared in this invention, when applied to the galvanizing process, results in coatings with excellent performance in terms of surface smoothness and thickness uniformity. The surface roughness Ra values ​​of the coatings in Examples 1-3 are all within the range of 0.15-0.18 μm, and the standard deviation of thickness is within the range of 0.62-0.85 μm. This indicates that the present invention, through specific raw material ratios, a leveling agent preparation process, and a leveling agent synthesis step, can effectively improve the surface smoothness of the galvanized layer and allow the zinc layer to be deposited more uniformly on the substrate surface.

[0039] Comparative Example 1 lacked 4-aminopyridine in the preparation of the leveling agent. Comparative Example 2 replaced the polyamine pyridine quaternary ammonium salt with dodecyltrimethylammonium chloride. The surface roughness and thickness uniformity of both were significantly worse, indicating that 4-aminopyridine is an important component for the leveling agent to achieve the effects of leveling and smoothing. The polyamine pyridine quaternary ammonium salt is the core leveling and leveling active ingredient of the leveling agent. Its structure and performance cannot be replaced by conventional quaternary ammonium salts. Comparative Example 3 deviated from the raw material weight ratio of the present invention. Comparative Example 4 changed the way the leveling agent was added in stages, which also caused a decrease in the smoothness of the coating.

[0040] Experiment Example 4: The corrosion resistance of each galvanized steel plate sample was tested according to GB / T 10125-2021 "Artificial Atmosphere Corrosion Test - Salt Spray Test". The results are shown in Table 2.

[0041] Table 2: As shown in the table above, the galvanized coating prepared by the embodiment of the present invention after treatment with the leveling agent for hot-dip galvanizing of columns exhibits excellent corrosion resistance in the salt spray corrosion test. The corrosion phenomenon appears late, develops slowly, and is mild. In the full-cycle salt spray test of 2000h, the coatings of Examples 1-3 showed no visible corrosion changes at 72h, only <2% of trace white spots appeared at 168h, and the proportion of white rust was still less than 2% at 500h with no red rust or coating peeling. Only a small amount of red rust of <4% appeared at 1000h, and the area of ​​red rust did not exceed 9% at 2000h. There was no pitting corrosion of the substrate or penetrating corrosion throughout the process, and the coating structure remained intact.

[0042] The corrosion resistance of all comparative coatings decreased to varying degrees, and the difference in corrosion between them and the examples continued to widen with the extension of the test period. Comparative Example 4, which only changed the method of adding the leveling agent, had the best corrosion resistance among the comparative examples, with a relatively light degree of corrosion from 72h to 500h. However, the red rust area reached about 10% at 1000h and rose to 20% at 2000h, with a corrosion development rate significantly faster than that of the examples. Comparative Example 3 deviated from the raw material ratio, and the degree of corrosion was further aggravated, with 8% yellow rust appearing at 500h. In Comparative Example 1, after 2000 hours, the red rust area reached 40% and the zinc layer was damaged. In Comparative Example 2, after replacing the polyamine pyridine quaternary ammonium salt, the yellow rust area increased to 12% after 500 hours, and after 2000 hours, the red rust exceeded 50% and the zinc layer was severely damaged in some areas, with a small amount of substrate exposed. Comparative Example 1, due to the lack of 4-aminopyridine in the preparation of the plating agent, became the group with the worst corrosion resistance. White corrosion appeared after 72 hours, yellow rust exceeded 15% after 500 hours and the coating peeled off, and after 2000 hours, the coating completely failed, more than half of the zinc layer was consumed and the substrate showed obvious pitting corrosion.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a leveler for a column hot-dip galvanizing, characterized by, Includes the following steps: S1: Weigh out 15-25 parts by weight of polyamine pyridine quaternary ammonium salt, 10-18 parts of 1,3-propanediaminetetraacetic acid, 8-15 parts of plating agent, 5-10 parts of isomeric tridecyl alcohol polyoxyethylene ether, 3-7 parts of disodium ethylenediaminetetraacetate and 35-50 parts of deionized water. The preparation method of the plating agent is as follows: A1. Pump anhydrous ethanol into the reactor, add epichlorohydrin dropwise to the reactor under a nitrogen atmosphere, heat to 45-52℃, then add boron trifluoride diethyl ether complex, and maintain the temperature for reaction; A2. After the reaction is complete, deionized water is pumped in, the pH is adjusted to 7.5-8.2, the mixture is allowed to stand and separate into layers, and the upper organic phase is washed to obtain the precursor. A3. Add 4-aminopyridine and sodium hydroxide to the precursor, and keep the reaction at 65-75℃. After the reaction is completed, cool down to 25-35℃ and dry under vacuum to obtain the intermediate. A4. Add deionized water to the intermediate and stir at 40-50℃ until dissolved. Add ethylenediamine, heat to 75-85℃, maintain the temperature for reaction, cool to room temperature, adjust pH to 6.2-7.8, and vacuum concentrate to obtain the plating agent. S2: Heat deionized water to 52-64℃, add isotridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt, and continue stirring; S3: Add 1,3-propanediaminetetraacetic acid to S2 and stir. Add the leveling agent in 3-5 portions while stirring. After each addition, raise the temperature. After all the agent has been added, continue stirring and allow it to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

2. The method of preparing a lubricant for column galvanizing according to claim 1, characterized by, S2 is specifically as follows: heat deionized water to 52-64℃, add isomeric tridecyl alcohol polyoxyethylene ether and disodium ethylenediaminetetraacetate in sequence, stir at 300-500 r / min for 20-30 min to obtain a composite solvent, add polyamine pyridine quaternary ammonium salt to the composite solvent, and stir for 30-40 min.

3. The method of preparing a lubricant for column galvanizing according to claim 1, characterized by, S3 is specifically prepared as follows: Add 1,3-propanediaminetetraacetic acid to S2 and stir at 200-300 r / min for 15-20 min. Then add the leveling agent in 3-5 portions while stirring, with an interval of 3-7 min between each addition. After each addition, raise the temperature by 2-3℃. After all the additions are completed, continue stirring for 25-35 min and allow to cool naturally to room temperature to obtain the leveling agent for hot-dip galvanizing of columns.

4. The method for preparing the leveling agent for hot-dip galvanizing of columns according to claim 1, characterized in that, A1 is specifically as follows: by weight, pump 35-45 parts of anhydrous ethanol into the reactor, add 18-25 parts of epichlorohydrin dropwise to the reactor under a nitrogen atmosphere, at 25-35℃ and 60-100 r / min, raise the temperature to 45-52℃ at 2-4℃ / min, then add 0.05-0.15 parts of boron trifluoride diethyl ether complex, and keep the reaction at this temperature for 5-8 hours.

5. The method for preparing the leveling agent for hot-dip galvanizing of columns according to claim 1, characterized in that, A2 is specifically as follows: After the reaction is completed, 40-50 parts of deionized water are pumped in, and the pH is adjusted to 7.5-8.2 with 0.1M sodium hydroxide aqueous solution. After standing for 30-60 minutes, the phases are separated. The lower aqueous phase is discharged through the bottom discharge port of the reactor, and the upper organic phase is washed with deionized water 2-3 times to obtain the precursor.

6. The method for preparing the leveling agent for hot-dip galvanizing of columns according to claim 1, characterized in that, A3 is specifically prepared as follows: by weight, add 4.5-7.5 parts of 4-aminopyridine and 2.0-3.5 parts of flake sodium hydroxide to the precursor, and keep the reaction at 65-75℃ for 8-12 hours. After the reaction is completed, cool down to 25-35℃, filter through the bottom filter to remove the inorganic salt precipitate generated in the reaction, return the filtrate to the reaction vessel, and remove ethanol at 55-65℃ and a vacuum of -0.08MPa to obtain the intermediate.

7. The method for preparing the leveling agent for hot-dip galvanizing of columns according to claim 1, characterized in that, A4 is specifically prepared as follows: Add deionized water to the intermediate and stir at 40-50℃ until dissolved. Add 3.2-5.6 parts by weight of ethylenediamine, heat to 75-85℃, keep the reaction at this temperature for 6-10 hours, cool to room temperature, adjust the pH to 6.2-7.8 with 0.1M hydrochloric acid, and concentrate to 1 / 3 volume at 55-65℃ and a vacuum of -0.08MPa to obtain the uniform plating agent.

8. The method for preparing the leveling agent for hot-dip galvanizing of columns according to claim 1, characterized in that, The polyamine pyridine quaternary ammonium salt is one or more of hexadecylpyridinium chloride and dodecylpyridinium bromide.

9. A leveling agent for hot-dip galvanizing of columns prepared according to any one of claims 1-8.

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