Hot galvanizing auxiliary agent and use method thereof

Abstract

The invention belongs to the technical field of chemical assistants, and relates to a hot galvanizing assistant agent which comprises the following components according to the total mass concentration of a solution: 240-250g / L of ammonium chloride, 140-150g / L of zinc chloride, 50-80g / L of potassium chloride, 0.5-1.2 g / L of a nonionic surfactant, 15-25g / L of an organic complexing agent and 1.5-3g / L of a corrosion inhibitor. The invention further relates to an application method of the hot galvanizing auxiliary agent. The application method comprises the following steps: pretreatment; a plating assistant is prepared, specifically, all components of the plating assistant are dissolved in proportion, ammonia water is added, and the pH is adjusted to 4-5; a workpiece to be galvanized is soaked in a plating assistant agent, the temperature ranges from 40 DEG C to 50 DEG C, the time ranges from 6 min to 10 min, and the workpiece lifting speed ranges from 0.5 m / min; gradient drying is conducted, specifically, the workpiece subjected to plating assisting enters a drying kang to be subjected to gradient drying; and hot galvanizing: the temperature of the zinc liquid is 445 + / -5 DEG C, and the zinc dipping time is 30-60 seconds. According to the hot galvanizing auxiliary agent and the using method thereof, the current wide concentration range is designed into the accurate concentration range, the leap-over development of the galvanizing process from extensive regulation and control to precise control is achieved, the galvanizing requirement is met, and the product quality of galvanized workpieces is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical additives, and relates to a plating additive machine and a use method thereof, in particular to a hot-dip galvanizing plating additive and a use method thereof. Background Art

[0002] With the transformation and upgrading of the manufacturing industry and increasingly stringent environmental protection requirements, traditional galvanizing processes face significant challenges. As a core component of the galvanizing process, optimizing the composition and performance of fluxes is crucial for reducing costs and minimizing environmental pollution. Research into flux composition optimization and process upgrades can effectively address current technical bottlenecks in the galvanizing process and drive the industry towards a more efficient, green, and intelligent future.

[0003] Galvanizing is widely used in areas such as steel pipes, steel structures, and automotive parts. As a key auxiliary material in the galvanizing process, the composition and properties of the plating flux directly affect the adhesion of the zinc coating. The main activating components in the plating flux are ammonium chloride and zinc chloride. If the ammonium chloride content is too low, plating leakage is likely to occur. However, if the ammonium chloride content is too high, the ammonia and hydrogen chloride gases produced by the decomposition of ammonium chloride cannot be discharged in a timely manner at the current temperature (60-80°C, to ensure the activation capacity of ammonium chloride and zinc chloride). This not only pollutes the environment but also re-reacts to form black ammonium chloride deposits on the workpiece surface, affecting the appearance quality of the zinc coating. Furthermore, excessive ammonium chloride content can cause crystallization, resulting in ammonium chloride waste. Excessive ammonium chloride content also produces a large amount of smoke during the plating process, affecting the workshop environment.

[0004] Zinc chloride absorbs moisture, maintaining the zinc soil's humidity and facilitating galvanizing. However, if the zinc soil is too moist, the pipe will not dry out, leading to plating leaks and zinc explosions. If the zinc chloride content is too low, the resulting zinc layer will be less dense, resulting in poor bonding between zinc and iron, making the zinc layer prone to detachment and corrosion.

[0005] An inappropriate ratio of zinc chloride and ammonium chloride can also lead to abnormal reactions during the drying process, affecting the uniformity of the galvanized layer.

[0006] At the same time, impurity ions such as Fe2+, SO4 2- After accumulation, the solution needs to be replaced frequently, which is costly.

[0007] In traditional processes, the concentration ranges of ammonium chloride and zinc chloride are too wide: 220-300g / L for ammonium chloride and 130-180g / L for zinc chloride. However, when the ammonium chloride concentration exceeds 250g / L, ammonia volatilization increases dramatically. When the zinc chloride concentration is less than 140g / L, the coating porosity exceeds 15%. Concentration fluctuations increase the frequency of solution changes by more than 30%. Therefore, it is crucial to design the concentrations of ammonium chloride and zinc chloride to improve coating quality. Summary of the Invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a hot-dip galvanizing flux and its use method which are scientifically and rationally designed, improve flux quality, are safe and environmentally friendly, reduce flux costs, and are easy to implement.

[0009] The present invention solves the technical problem by adopting the following technical solutions:

[0010] A hot-dip galvanizing flux, characterized in that it is prepared from ammonium chloride, zinc chloride, potassium chloride, a nonionic surfactant, an organic complexing agent, a corrosion inhibitor and water as components, wherein the flux comprises, by total mass concentration of the solution, 240-250 g / L of ammonium chloride, 140-150 g / L of zinc chloride, 50-80 g / L of potassium chloride, 0.5-1.2 g / L of nonionic surfactant, 15-25 g / L of organic complexing agent and 1.5-3 g / L of corrosion inhibitor.

[0011] Furthermore, the nonionic surfactant is polyoxyethylene ether.

[0012] Furthermore, the organic complexing agent is sodium citrate.

[0013] Furthermore, the corrosion inhibitor is benzotriazole.

[0014] Furthermore, the use temperature of the plating flux is controlled at 40-50°C.

[0015] Furthermore, it also includes 0.8-1.2 wt% of hydroxyethyl cellulose and 0.05-0.1 wt% of nano silicon dioxide.

[0016] A method for using a hot-dip galvanizing flux, characterized in that it comprises the following steps:

[0017] Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing.

[0018] Preparation of plating flux: Dissolve the components of the plating flux in proportion, add ammonia water, and adjust the pH to 4-5;

[0019] Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 40-50°C for 6-10 minutes, and the workpiece lifting speed is 0.5m / min;

[0020] Gradient drying: The workpiece after plating is put into the drying oven for gradient drying;

[0021] Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

[0022] Furthermore, the concentration of the plating flux is monitored in real time using a conductivity sensor with a measuring range of 0-500 mS / cm.

[0023] Furthermore, when Fe2 + When the concentration is greater than 50 ppm, sodium citrate is added to the flux.

[0024] Furthermore, the gradient drying is specifically as follows:

[0025] Phase 1: Dehumidification, hot air circulation at 85℃±2℃, humidity 30%RH, time 6min;

[0026] The second stage: infrared radiation at a temperature of 115℃±3℃ for 7 minutes.

[0027] The advantages and positive effects of the present invention are:

[0028] This hot-dip galvanizing flux and its use method, by designing the current wide concentration range into a more precise concentration range, achieves a leap-forward development of the galvanizing process from "extensive regulation" to "precise control", meets the galvanizing requirements, and improves the product quality of galvanized workpieces. The invention forms a low-melting eutectic system by potassium chloride and ammonium chloride to reduce the volatilization of ammonia; reduces the surface tension by surfactant to avoid plating leakage; and complexes Fe2 + , extending the solution life by over 50%; benzotriazole forms a film under acidic conditions, inhibiting corrosion of workpieces during pretreatment. Adding 0.8-1.2% hydroxyethyl cellulose (HEC) and 0.05-0.1% nano-silica forms a low-temperature, highly active gel network, addressing the issue of insufficient ion mobility at high concentrations and low temperatures. DETAILED DESCRIPTION

[0029] The embodiments of the present invention are further described below:

[0030] A hot-dip galvanizing flux, the innovation of which lies in: ammonium chloride, zinc chloride, potassium chloride, polyoxyethylene ether, sodium citrate, benzotriazole, and water are used as the components to prepare the flux. The total mass concentration of the solution includes: 240-250g / L of ammonium chloride, 140-150g / L of zinc chloride, 50-80g / L of potassium chloride, 0.5-1.2g / L of polyoxyethylene ether, 15-25g / L of sodium citrate, 1.5-3g / L of benzotriazole. Hydroxyethyl cellulose and nano-silicon dioxide are also present in the flux.

[0031] Ammonium chloride, zinc chloride, and potassium chloride form a ternary phase equilibrium. When ammonium chloride is controlled at 240-250g / L, the thermal decomposition rate is ≤0.8g / (L·h) (compared to greater than 1.5g / (L·h) in conventional processes). Zinc chloride at 140-150g / L stabilizes the moisture content of zinc ash at 6-8%. When the molar ratio of KCl to NH4Cl is 1:3, the boiling point of the solution rises to 82°C. The operating temperature of the plating flux is controlled at 40-50°C. The addition of 0.8-1.2% hydroxyethyl cellulose (HEC) and 0.05-0.1% nano-silica forms a gel network with high low-temperature activity, addressing the issue of insufficient ion mobility at high concentrations and low temperatures.

[0032] A method for using a hot-dip galvanizing flux, the innovation of which lies in: comprising the following steps:

[0033] Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing.

[0034] Preparation of the plating flux: Dissolve the components of the plating flux in the correct proportions and add ammonia water to adjust the pH to 4-5. Monitor the concentration of the plating flux in real time using a conductivity sensor with a range of 0-500mS / cm. When the Fe2 concentration is greater than 50ppm, add sodium citrate to the plating flux.

[0035] Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 40-50°C for 1-3 minutes, and the workpiece lifting speed is 0.5m / min;

[0036] Gradient drying: Place the workpiece after assisted plating into the drying kang for gradient drying: the first stage: dehumidification, hot air circulation at a temperature of 85℃±2℃, humidity of 30%RH, time for 6 minutes; the second stage: infrared radiation at a temperature of 115℃±3℃, time for 7 minutes;

[0037] Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

[0038] Example 1:

[0039] A method for using a hot-dip galvanizing flux, the innovation of which lies in: comprising the following steps:

[0040] Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing.

[0041] Preparation of the flux: Dissolve the flux components in the appropriate proportions: 245g / L ammonium chloride, 145g / L zinc chloride, 65g / L potassium chloride, 0.8g / L polyoxyethylene ether, 20g / L sodium citrate, and 2g / L benzotriazole. Add ammonia and adjust the pH to 4. Then, add 1% hydroxyethyl cellulose and 0.08% nano-silica. The hydroxyethyl cellulose forms a three-dimensional gel network, slowing the decomposition of ammonium chloride and enhancing the Fe₂+ encapsulation capacity. The nano-silica improves the solution's thermal conductivity and promotes uniform ion diffusion at low temperatures.

[0042] Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 45°C for 8 minutes. In the first 4 minutes, the hydroxyethyl cellulose gel network absorbs impurities; in the last 4 minutes, nano-silica promotes the directional deposition of zinc ions. The workpiece is lifted at a speed of 0.5m / min.

[0043] Gradient drying: Place the workpiece after assisted plating into the drying kang for gradient drying: the first stage: dehumidification, hot air circulation at a temperature of 85℃±2℃, humidity of 30%RH, time for 6 minutes; the second stage: infrared radiation at a temperature of 115℃±3℃, time for 7 minutes;

[0044] Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

[0045] Dynamic immersion flow rate 0.4m / s, conductivity maintained at 380±10mS / cm, Fe2 + The concentration is stable at 32-48ppm (without adding sodium citrate, Fe2 + The coating survived salt spray tests for over 3,000 hours with no red rust (conventional processes require ≤ 2,000 hours). The low-temperature process reduces ammonia volatilization, and combined with the physical adsorption of hydroxyethyl cellulose gel on the gas, waste gas treatment efficiency is increased by 50%. Nano-silica is recycled, and the magnetic separation recovery rate reaches 92%, avoiding the sludge contamination associated with traditional silicate additives.

[0046] Comparative design

[0047]

[0048] As can be seen from Comparative Example 2 in the above table, simply lowering the temperature will result in the high-concentration salt solution being unable to effectively activate the matrix; as can be seen from Comparative Example 3, additives alone cannot make up for insufficient concentration, and the three elements of "high concentration + low temperature + gel network" must be met simultaneously to achieve the purpose of the invention.

[0049] Comparison of experimental data

[0050] index The present invention Comparative Example 1 Comparative Example 2 Coating coverage 99.5％ 98.2％ 84.7％ Coating hardness (HV) 85±3 112±5 70±4 <![CDATA[Ammonia emissions (mg / m 3 )]]> 8.3 25.6 9.1 (but the coating is unqualified) Zinc consumption (kg / ton steel) 19.5 22.8 26.3

[0051] Traditional theory holds that the concentration must be reduced at low temperatures to avoid the problem of insufficient activation. However, the present invention increases the viscoelasticity of the liquid phase through hydroxyethyl cellulose gel, which increases the ion mobility of high-concentration ammonium chloride and zinc chloride by 2.1 times at 45°C, making "high concentration and low temperature" feasible.

[0052] Despite the increased ammonium chloride concentration, the low-temperature hydroxyethyl cellulose gel reduced ammonia emissions by 67% (compared to the traditional 70°C process), and the coating hardness was closer to pure zinc (85HV vs pure zinc 70-90HV), avoiding the brittleness problem of traditional high-hardness coatings.

[0053] Example 2:

[0054] A method for using a hot-dip galvanizing flux, the innovation of which lies in: comprising the following steps:

[0055] Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing.

[0056] Preparation of plating flux: Dissolve the components of the plating flux in proportion: 248g / L ammonium chloride, 142g / L zinc chloride, 65g / L potassium chloride, 0.8g / L polyoxyethylene ether, 20g / L sodium citrate, 2g / L benzotriazole, and add ammonia water to adjust the pH to 4.

[0057] Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 48°C for 6 minutes and a workpiece lifting speed of 0.5 m / min.

[0058] Gradient drying: Place the workpiece after assisted plating into the drying kang for gradient drying: the first stage: dehumidification, hot air circulation at a temperature of 85℃±2℃, humidity of 30%RH, time for 6 minutes; the second stage: infrared radiation at a temperature of 115℃±3℃, time for 7 minutes;

[0059] Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

[0060] Test results: The amount of zinc slag produced is 1.2kg / ton (3.5kg / ton for traditional process), and the energy consumption of the drying process is reduced by 22% (infrared radiation time is shortened to 5 minutes).

[0061] Example 3:

[0062] A method for using a hot-dip galvanizing flux, the innovation of which lies in: comprising the following steps:

[0063] Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing.

[0064] Preparation of the plating flux: Dissolve the components of the plating flux in proportion: 242g / L ammonium chloride, 148g / L zinc chloride, 65g / L potassium chloride, 0.8g / L polyoxyethylene ether, 20g / L sodium citrate, and 2g / L benzotriazole. Add ammonia water and adjust the pH to 4. Monitor the concentration of the plating flux in real time using a conductivity sensor with a range of 0-500mS / cm, and replenish any components that exceed the concentration range.

[0065] Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 42°C for 10 minutes and a workpiece lifting speed of 0.5 m / min.

[0066] Gradient drying: Place the workpiece after assisted plating into the drying kang for gradient drying: the first stage: dehumidification, hot air circulation at a temperature of 85℃±2℃, humidity of 30%RH, time for 6 minutes; the second stage: infrared radiation at a temperature of 115℃±3℃, time for 7 minutes;

[0067] Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

[0068] The solution can be used continuously for 150 hours and still meet the process requirements (traditionally, it needs to be adjusted every 50 hours), and the workpiece leakage rate is less than 0.03% (the industry average level is 0.15%).

[0069] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A hot-dip galvanizing flux, characterized in that: The plating flux is prepared with ammonium chloride, zinc chloride, potassium chloride, a nonionic surfactant, an organic complexing agent, a corrosion inhibitor and water as components. The total mass concentration of the solution includes: 240-250g / L of ammonium chloride, 140-150g / L of zinc chloride, 50-80g / L of potassium chloride, 0.5-1.2g / L of nonionic surfactant, 15-25g / L of organic complexing agent and 1.5-3g / L of corrosion inhibitor.

2. A hot-dip galvanizing flux according to claim 1, characterized in that: The nonionic surfactant is polyoxyethylene ether.

3. A hot-dip galvanizing flux according to claim 1, characterized in that: The organic complexing agent is sodium citrate.

4. A hot-dip galvanizing flux according to claim 1, characterized in that: The corrosion inhibitor is benzotriazole.

5. The hot-dip galvanizing flux according to claim 1, characterized in that: The use temperature of the plating flux is controlled at 40-50°C.

6. A hot dip galvanizing flux according to claim 1, characterized in that: The invention also comprises 0.8-1.2 wt % of hydroxyethyl cellulose and 0.05-0.1 wt % of nano silicon dioxide.

7. A method for using a hot-dip galvanizing flux, characterized in that: The method of use is based on the hot-dip galvanizing flux according to any one of claims 1 to 6, and comprises the following steps: Pretreatment: Pickling in a pickling solution containing 15% hydrochloric acid at a temperature of 40°C for 5 minutes. After pickling, rinse with water and then perform ultrasonic degreasing. Preparation of plating flux: Dissolve the components of the plating flux in proportion, add ammonia water, and adjust the pH to 4-5; Electroplating operation: immerse the workpiece to be galvanized in the electroplating agent at a temperature of 40-50°C for 6-10 minutes, and the workpiece lifting speed is 0.5m / min; Gradient drying: The workpiece after plating is put into the drying oven for gradient drying; Hot dip galvanizing: zinc liquid temperature 445±5℃, zinc dipping time 30-60s.

8. The method for using a hot-dip galvanizing flux according to claim 7, wherein: The concentration of the plating flux is monitored in real time using a conductivity sensor with a measuring range of 0-500mS / cm.

9. The method for using a hot-dip galvanizing flux according to claim 7, wherein: When Fe2 + When the concentration is greater than 50 ppm, sodium citrate is added to the flux.

10. The method for using a hot-dip galvanizing flux according to claim 7, wherein: The gradient drying is specifically as follows: Phase 1: Dehumidification, hot air circulation at 85℃±2℃, humidity 30%RH, time 6min; The second stage: infrared radiation at a temperature of 115℃±3℃ for 7 minutes.

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