Energy-saving environment-friendly zinc steel guardrail surface electrostatic spraying pretreatment process and device

Abstract

The invention discloses an energy-saving and environment-friendly zinc steel guardrail surface electrostatic spraying pretreatment process and device, and relates to the technical field of guardrail machining processes. The surface electrostatic spraying pretreatment process for the energy-saving and environment-friendly zinc steel guardrail comprises the following steps that S1, a zinc steel guardrail workpiece is sequentially subjected to degreasing treatment and surface conversion film treatment; s2, the workpiece subjected to surface conversion film treatment is subjected to multi-stage countercurrent spraying washing; s3, the cleanliness parameter of washing water in the last-stage spraying washing unit is monitored in real time; and S4, based on the monitored cleanliness parameters, dynamically controlling pollution discharge and water supplement operation of the last-stage spraying and washing unit. According to the surface electrostatic spraying pretreatment process for the energy-saving and environment-friendly zinc steel guardrail, the cleanliness parameter of washing water in the last-stage spraying washing unit is monitored in real time, pollution discharge and water replenishing operation is dynamically controlled based on the parameter, and accurate and intelligent management of the washing process is achieved.

Description

Technical Field

[0001] This invention relates to the field of guardrail processing technology, specifically to an energy-saving and environmentally friendly electrostatic spraying pretreatment process and apparatus for zinc-steel guardrails. Background Technology

[0002] After key pretreatment processes such as degreasing and surface conversion coating (e.g., phosphating or ceramic coating) are completed, various chemical working liquids will remain on the surface of zinc steel guardrails. In order to ensure the adhesion and quality of the electrostatic spray coating, these residues must be thoroughly removed by water washing. At present, the most common technology used in the industry is multi-stage countercurrent rinsing technology, which sets up multiple water washing tanks in series so that the direction of the workpiece's movement is opposite to the direction of water supply. Fresh pure water is usually added only to the last water washing tank, and the cleaner water flow is used to clean the workpiece with a lower degree of contamination, thereby achieving the purpose of saving water.

[0003] While this water-washing method can save water to some extent, it is essentially still a crude method that maintains the balance of the washing tank solution at the cost of continuously consuming fresh water and continuously discharging wastewater; its main problem is:

[0004] First, water waste remains serious. Continuous overflows result in a large amount of water that is only slightly polluted being discharged into the sewage treatment system, causing ineffective loss of water resources.

[0005] Secondly, the large volume of wastewater generated places a greater burden on the company's wastewater treatment facilities and increases operating costs.

[0006] Third, due to the lack of perception of the cleanliness of the washing water, the washing effect is subject to fluctuations. The workpiece may not be cleaned properly due to the instantaneous deterioration of the water quality, which in turn affects the quality of the coating applied in subsequent spraying. In order to address the shortcomings of the existing technology, this invention provides an energy-saving and environmentally friendly electrostatic spraying pretreatment process and device for zinc steel guardrails to solve the above problems. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an energy-saving and environmentally friendly electrostatic spraying pretreatment process and device for zinc-steel guardrails. By real-time monitoring of the cleanliness parameters of the washing water in the final spray washing unit and dynamically controlling the sewage discharge and water replenishment operations based on these parameters, precise and intelligent management of the washing process is achieved. Compared with the fixed mode of continuous overflow in existing technologies, this method only initiates updates when the water quality does not meet the standards, completely avoiding ineffective water waste and improving the water-saving rate. At the same time, it reduces wastewater discharge from the source, effectively solving the technical problems of high water consumption and high wastewater discharge mentioned in the background technology.

[0008] To achieve the above objectives, the present invention provides the following technical solution: an energy-saving and environmentally friendly electrostatic spraying pretreatment process for zinc-steel guardrails, the process comprising the following steps:

[0009] Step S1: The zinc-steel guardrail workpiece is subjected to degreasing and surface conversion coating treatment in sequence;

[0010] Step S2: Perform multi-stage countercurrent spray water washing on the workpiece treated with the surface conversion film;

[0011] Step S3: Monitor the cleanliness parameters of the wash water in the last-stage spray washing unit in real time;

[0012] Step S4: Based on the monitored cleanliness parameters, dynamically control the sewage discharge and water replenishment operations of the last-stage spray washing unit; when the cleanliness parameters are lower than the preset threshold, start the sewage discharge valve to discharge some dirty water, and simultaneously start the water replenishment valve to replenish fresh pure water; when the cleanliness parameters are higher than or equal to the preset threshold, maintain the washing water in the system for recycling.

[0013] Preferably, in step S2, the multi-stage countercurrent spray washing adopts a three-stage washing unit, the water flow direction is opposite to the workpiece travel direction, and fresh pure water is only replenished to the last stage washing unit.

[0014] Preferably, in step S3, the cleanliness parameters include conductivity and turbidity values; the preset thresholds include conductivity thresholds and turbidity thresholds; and the monitoring process is achieved through online conductivity sensors and online turbidity sensors installed in the circulation pipeline of the last-stage spray washing unit.

[0015] Preferably, the specific process of dynamic control in step S4 is as follows:

[0016] When the detected conductivity value exceeds the first set value or the turbidity value exceeds the second set value, it is determined that the cleanliness parameter is lower than the preset threshold. The PLC controller issues a command to open the drain valve and simultaneously open the water supply valve.

[0017] The total amount of sewage discharge and water replenishment is 5% to 15% of the total volume of the final stage spray washing unit;

[0018] When the monitored conductivity and turbidity values ​​both fall below 80% of their respective set values, the PLC controller shuts off the drain valve and the water supply valve.

[0019] Preferably, the dirty water discharged from the last stage spray washing unit is directed to the second stage washing unit as makeup water for the second stage washing unit; the wastewater overflowing from the second stage washing unit is directed to the first stage washing unit as makeup water for the first stage washing unit.

[0020] Preferably, the wastewater discharged from the first-stage washing unit first passes through a precision filtration system to remove solid impurities before being directed to the degreasing treatment process as replenishment water for the degreasing tank.

[0021] Preferably, in step S2, each stage of the washing unit is equipped with an independent water pump and circulation pipeline. The washing water is atomized and sprayed through nozzles, and a bag filter is installed on the circulation pipeline.

[0022] Preferably, the surface conversion film treatment is a phosphorus-free nano-ceramic conversion film treatment, and the treatment bath is carried out at room temperature without heating.

[0023] Preferably, before step S1, a pre-washing step is included, and the wastewater generated from the pre-washing is directly sent to the sewage treatment system.

[0024] A second aspect of this invention discloses an apparatus for implementing the electrostatic spraying pretreatment process for the surface of the energy-saving and environmentally friendly zinc-steel guardrail, the apparatus comprising:

[0025] The degreasing tank, the conversion membrane treatment tank, and the multi-stage countercurrent spray washing system are arranged in sequence.

[0026] The last stage of the multi-stage counter-current spray washing system is connected to an intelligent washing control module.

[0027] The intelligent water washing control module includes a water quality monitoring unit, a control unit, and an execution unit;

[0028] The water quality monitoring unit includes an online conductivity sensor and an online turbidity sensor installed on the circulation pipeline of the last-stage water washing unit;

[0029] The control unit is a programmable logic controller, and its signal input terminal is connected to the online conductivity sensor and the online turbidity sensor.

[0030] The execution unit includes a drain valve and a water supply valve controlled by the programmable logic controller. The drain valve is installed on the drain pipe of the last-stage water washing unit, and the water supply valve is installed on the fresh pure water pipe leading to the last-stage water washing unit.

[0031] The technical effects and advantages of this invention are as follows:

[0032] 1. This energy-saving and environmentally friendly electrostatic spraying pretreatment process for zinc-steel guardrails achieves precise and intelligent management of the washing process by real-time monitoring of the cleanliness parameters of the washing water in the final spray washing unit and dynamically controlling the sewage discharge and water replenishment operations based on these parameters. Compared with the fixed mode of continuous overflow in the existing technology, this method only starts the update when the water quality does not meet the standards, completely avoiding ineffective water waste, improving the water saving rate, and reducing wastewater discharge from the source. It effectively solves the technical problems of high water consumption and high wastewater discharge mentioned in the background technology.

[0033] 2. This energy-saving and environmentally friendly electrostatic spraying pretreatment process for zinc-steel guardrails combines a three-stage counter-current spray washing structure with an intelligent washing control module, and constructs a tiered water supply chain from the last stage to the first stage. This invention achieves multi-stage reuse and maximum efficiency enhancement of water resources. This design maximizes the washing efficiency of a unit volume of fresh pure water, further reducing dependence on fresh water while ensuring the final washing quality, strengthening the overall system's water-saving capability, and overcoming the drawbacks of simply increasing the number of washing stages, such as bulky equipment and increased costs.

[0034] 3. The electrostatic spraying pretreatment process for the surface of this energy-saving and environmentally friendly zinc-steel guardrail allows the wastewater discharged from the first-stage water washing unit to be reused in the degreasing tank after precision filtration, forming a cross-process wastewater reuse. This process not only further reduces the total wastewater discharge and fresh water replenishment of the entire pretreatment system, but also reuses the residual chemicals in the wastewater, reducing the replenishment cost of the degreasing agent. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a flowchart of the process method of the present invention;

[0037] Figure 2 This is a diagram of the multi-stage countercurrent spray washing and intelligent control architecture of the present invention;

[0038] Figure 3 This is the logic diagram for the intelligent water washing dynamic control of the present invention. Detailed Implementation

[0039] 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 embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This embodiment discloses an energy-saving and environmentally friendly pretreatment process for electrostatic spraying of zinc-steel guardrails, according to the attached... Figure 1 To be continued Figure 3 As shown, the process includes the following steps:

[0041] Step S1: The zinc-steel guardrail workpiece is subjected to degreasing and surface conversion coating treatment in sequence;

[0042] Step S2: Perform multi-stage countercurrent spray water washing on the workpiece treated with the surface conversion film;

[0043] Step S3: Monitor the cleanliness parameters of the wash water in the last-stage spray washing unit in real time;

[0044] Step S4: Based on the monitored cleanliness parameters, dynamically control the sewage discharge and water replenishment operations of the last-stage spray washing unit; when the cleanliness parameters are lower than the preset threshold, start the sewage discharge valve to discharge some dirty water, and simultaneously start the water replenishment valve to replenish fresh pure water; when the cleanliness parameters are higher than or equal to the preset threshold, maintain the water washing water in the system for recycling.

[0045] This invention comprises a complete pretreatment production line, the core of which lies in the improvement of the traditional water washing process. An apparatus for realizing an energy-saving and environmentally friendly electrostatic spraying pretreatment process for zinc-steel guardrail surfaces is sequentially configured with a degreasing tank, a conversion film treatment tank, and a multi-stage counter-current spray water washing system. The final stage of the multi-stage counter-current spray water washing system integrates a key intelligent water washing control module, which consists of a water quality monitoring unit, a control unit, and an execution unit.

[0046] According to the appendix Figure 2 As shown, the multi-stage counter-current spray washing system employs a three-stage washing unit: a first-stage washing unit, a second-stage washing unit, and a final-stage washing unit. The water flow direction is strictly opposite to the workpiece's travel direction, following a counter-current principle to conserve water: fresh pure water is only supplied to the final-stage washing unit, which has the highest cleanliness requirements. Its overflow then serves as replenishment water for the second-stage washing unit, and the overflow water from the second-stage washing unit is used to replenish the first-stage washing unit. Each washing unit is equipped with an independent water pump and circulation pipeline, and bag filters are installed on the pipelines to filter particulate impurities in the washing water, preventing nozzle clogging and ensuring effective spraying. The washing water is atomized through the nozzles, covering the workpiece and ensuring uniform and thorough cleaning.

[0047] According to the appendix Figure 1 and attached Figure 3 As shown, the working principle of the intelligent water washing control module is as follows: The water quality monitoring unit includes an online conductivity sensor and an online turbidity sensor installed in the circulation pipeline of the last-stage water washing unit, used to monitor the cleanliness parameters of the washing water in real time and continuously. The sensor signals are transmitted to the control unit, i.e., a programmable logic controller (PLC). The PLC has preset conductivity and turbidity thresholds, with the conductivity threshold being the first set value and the turbidity threshold being the second set value. When either the detected conductivity or turbidity value exceeds its set threshold, the PLC determines that the cleanliness of the washing water does not meet the standard and immediately sends a command to the execution unit. The execution unit includes a controlled drain valve and a water supply valve. The PLC command will simultaneously open these two valves, draining approximately 5% to 15% of the total volume of the last-stage water washing unit of dirty water and replenishing an equal amount of fresh pure water. This process continues until the cleanliness parameters drop below 80% of the set value, at which point the valves close and the system resumes its circulation state. This closed-loop control logic realizes a fundamental shift from "continuous consumption" to "on-demand replacement."

[0048] According to the appendix Figure 1 To be continued Figure 3 As shown, the surface conversion film treatment is preferably phosphorus-free nano-ceramic conversion film treatment. The treatment bath is carried out at room temperature without heating, eliminating the heating energy consumption and emissions of phosphorus-containing and heavy metal pollutants of traditional phosphating processes from the source. Together with the intelligent water washing system, it constitutes an energy-saving and environmentally friendly solution for the entire process.

[0049] According to the appendix Figure 2 To be continued Figure 3 As shown, to achieve the ultimate utilization of water resources, this invention constructs a multi-stage water circulation chain: the wastewater with the highest pollutant concentration discharged from the first-stage washing unit first passes through a precision filtration system to remove solid impurities. This precision filtration system can use filter cartridges with a precision of 5-10 μm. The wastewater is then directed to the degreasing process as makeup water for the degreasing tank. Since the degreasing agent itself needs to be periodically discharged and replaced, using this wastewater for replenishment achieves the reuse of organic matter in the wastewater and further reduces the overall wastewater discharge and fresh water consumption of the system.

[0050] According to the appendix Figure 1 To be continued Figure 3 As shown, it is particularly important to emphasize that the total amount of wastewater discharge and replenishment is precisely controlled within 5% to 15% of the total unit volume. This range is the optimal range verified through extensive practical experience: if the proportion is too low, the replacement effect is not significant and cannot effectively reduce the cleanliness parameters; if the proportion is too high, it is close to continuous overflow, which defeats the purpose of intelligent control and results in water waste. This precise control is the key to ensuring that the system achieves a dynamic balance between water conservation and water quality stability.

[0051] According to the appendix Figure 1 To be continued Figure 3 As shown, it is particularly important to emphasize that a pre-washing station can be set up before the workpiece enters the degreasing process. This station is mainly used to rinse off macroscopic dust and particles from the workpiece surface. The wastewater generated has a high solids content and complex composition. It goes directly into the sewage treatment system and does not participate in the subsequent water circulation, so as to avoid coarse impurities entering the precision circulation system of this invention and causing filter blockage or sensor contamination.

[0052] Example 1: This example uses a standard specification zinc-steel fence as an example. The standard specification zinc-steel fence has a cross-sectional dimension of 50mm × 50mm and a length of 6m. (See attached...) Figure 1 To be continued Figure 3 Detailed workflow description:

[0053] Pre-washing: The zinc steel guardrail workpiece is sent into the pre-washing unit, and large impurities such as floating dust and oil stains are removed by high-pressure spraying at 0.2-0.3MPa. The spraying time is 3-5 minutes, and the wastewater generated is directly introduced into the sewage treatment system.

[0054] Degreasing treatment: The pre-washed workpiece is sent into the degreasing tank and treated with an alkaline degreasing agent at a concentration of 5%-8% at room temperature for 10-15 minutes. During the treatment, the degreasing effect is enhanced by the aeration device in the tank to remove residual oil stains on the surface of the workpiece.

[0055] Surface conversion film treatment: After degreasing, the workpiece is transferred into a phosphorus-free nano-ceramic conversion film treatment tank and treated at room temperature for 5-8 minutes. The thickness of the conversion film is controlled at 0.5-1μm, forming a uniform and dense ceramic conversion film on the surface of the workpiece, which enhances the adhesion of subsequent spraying.

[0056] Multi-stage countercurrent spray washing: The workpiece passes through the washing unit in the order of "first stage → second stage → last stage". The water flow direction is opposite to the workpiece's direction of travel. Fresh pure water is introduced into the third stage washing unit and sprayed onto the workpiece through atomizing nozzles. The spray particle size is 20-50μm. The washing water is recycled after being filtered through circulation pipelines and bag filters. The filtration accuracy is 10μm. The second stage washing unit is replenished with the dirty water discharged from the third stage, and the first stage washing unit is replenished with the wastewater overflowing from the second stage. The residence time for each stage of washing is 2-3 minutes.

[0057] Water quality monitoring: Online conductivity sensor (set to the first set value of 50μS / cm) and online turbidity sensor (set to the second set value of 10NTU) installed on the circulation pipeline of the third-stage water washing unit monitor the parameters of the water washing in real time. The data acquisition frequency is 5 seconds / time, and the data is transmitted to the PLC controller.

[0058] Dynamic sewage discharge and water replenishment: When the conductivity value exceeds 50μS / cm or the turbidity value exceeds 10NTU, the PLC controller starts the sewage discharge valve and water replenishment valve to discharge and replenish 10% of the total volume of the third-stage water washing unit; when the conductivity value drops to below 40μS / cm and the turbidity value drops to below 8NTU, the PLC controller closes the valve to maintain the circulation of the washing water.

[0059] Wastewater recycling: The wastewater discharged from the first-stage washing unit is filtered through a precision filtration system to remove solid impurities with a filtration accuracy of 5μm. It is then pumped into the degreasing tank as makeup water to replenish the liquid level lost in the degreasing tank due to evaporation and workpiece carry-out. The concentration of the degreasing tank liquid is checked every 8 hours, and degreasing agent is added as needed.

[0060] Example 2: This example uses a large-size heavy-duty zinc-steel guardrail as an example. The large-size heavy-duty zinc-steel guardrail has a cross-sectional dimension of 100mm × 100mm and a length of 8m. (In conjunction with the attached...) Figure 1 To be continued Figure 3 Detailed workflow description:

[0061] Pre-washing: Segmented high-pressure spraying is adopted, with 3 independent spraying zones. The spraying pressure is increased to 0.3-0.4MPa, and the spraying time for each zone is 2-3 minutes to ensure that there are no impurities left on the surface of large workpieces. Wastewater is directly sent to the sewage treatment system.

[0062] Degreasing treatment: The workpiece is sent into a large degreasing tank and soaked in a low-temperature, high-efficiency alkaline degreasing agent (concentration 8%-10%) at room temperature for 20-25 minutes. During this period, the degreasing effect is enhanced by the stirring device in the tank (speed 30-50r / min) to avoid oil residue on the surface of heavy workpieces.

[0063] Surface conversion film treatment: Transfer to a phosphorus-free nano-ceramic conversion film treatment tank and treat at room temperature for 8-12 minutes. The thickness of the conversion film is controlled at 1-1.5μm to ensure that the conversion film is evenly covered on the surface of heavy workpieces without any missed areas.

[0064] Multi-stage countercurrent spray washing: The spray pressure of each washing unit is increased to 0.4-0.5MPa, and the residence time of the workpiece in the washing unit is extended to 3-5 minutes per stage. The fresh pure water spray flow rate of the third-stage washing unit is increased to 1.2 times the conventional value. The bag filter of the circulation pipeline is cleaned every 4 hours, with a filtration accuracy of 8μm to ensure the filtration effect.

[0065] Water quality monitoring: The first set value for conductivity is 60 μS / cm, the second set value for turbidity is 15 NTU, the sensor data acquisition frequency is increased to 3 seconds / time, and the parameters of the third-stage wash water are continuously monitored.

[0066] Dynamic sewage discharge and water replenishment: When the monitored parameters exceed the standard, the PLC controller controls the sewage discharge and water replenishment volume to 15% of the total volume of the third-stage water washing unit to accelerate the water quality recovery speed; when the conductivity drops below 48μS / cm and the turbidity drops below 12NTU, the valve is closed;

[0067] Wastewater recycling: The first-stage wastewater is deeply filtered by a precision filtration system with a filtration accuracy of 3μm and used as makeup water for the degreasing tank. At the same time, the concentration and pH value of the degreasing tank solution are tested every 6 hours, and degreasing agent is added as appropriate to maintain the stability of the tank solution.

[0068] Example 3: This example uses the production of zinc-steel guardrails in a high humidity environment (relative humidity ≥ 85%) as an example. (In conjunction with the attached...) Figure 1 To be continued Figure 3 Detailed workflow description:

[0069] Pre-washing: Increase the pre-washing spray temperature to 30-35℃, spray pressure to 0.25-0.35MPa, and spray time to 4-6 minutes to improve the efficiency of impurity dissolution and removal under high humidity conditions. Wastewater is directly introduced into the sewage treatment system.

[0070] Degreasing treatment: Use a moisture-resistant alkaline degreasing agent with a concentration of 6%-9%, soak at room temperature for 12-18 minutes. The degreasing tank is equipped with a sealed cover to reduce the risk of moisture absorption and deterioration of the tank solution, and remove residual oil stains from the surface of the workpiece.

[0071] Surface conversion coating treatment: Add moisture-resistant stabilizer to the phosphorus-free nano-ceramic conversion coating treatment bath at a concentration of 0.5%-1% of the total bath volume. Treat at room temperature for 6-10 minutes. Control the conversion coating thickness to 0.8-1.2μm to ensure that the conversion coating does not rust or peel off in high humidity environments.

[0072] Multi-stage countercurrent spray water washing: Each stage of the water washing unit is reinforced with sealing protection and dehumidification devices are installed to reduce the humidity inside the unit. The fresh pure water in the third stage water washing unit is pure water that has been dehumidified and has a water content of ≤0.5%. After spraying, it is quickly returned through the circulation pipeline at a return speed of 1.5m / s to reduce water evaporation.

[0073] Water quality monitoring: Due to the slow evaporation of water in a high humidity environment, the first set value for conductivity is 45μS / cm, and the second set value for turbidity is 8NTU. The sensor is encrypted to monitor the frequency, and data is collected once every 2 seconds.

[0074] Dynamic sewage discharge and water replenishment: When parameters exceed the standard, the sewage discharge and water replenishment volume is 5% of the total volume of the third-stage water washing unit to avoid excessive water replenishment leading to excessively high system liquid level; when the conductivity drops below 36μS / cm and the turbidity drops below 6.4NTU, the valve is closed;

[0075] Wastewater recycling: After the first-stage wastewater is precision filtered, it is dehydrated before being pumped into the degreasing tank. The water content is reduced to below 1% to remove excess water and maintain a stable concentration of the degreasing tank solution. At the same time, the water content and degreasing effect of the degreasing tank solution are tested every 4 hours to ensure the quality of treatment.

[0076] The beneficial effects of this energy-saving and environmentally friendly electrostatic spraying pretreatment process and equipment for zinc-steel guardrails are as follows:

[0077] This process achieves precise and intelligent management of the washing process by real-time monitoring of the cleanliness parameters of the washing water in the last-stage spray washing unit and dynamically controlling the sewage discharge and water replenishment operations based on these parameters. Compared with the fixed mode of continuous overflow in the prior art, this method only starts updating when the water quality does not meet the standards, completely avoiding ineffective water waste and improving the water saving rate. At the same time, it reduces the amount of wastewater discharge from the source, effectively solving the technical problems of high water consumption and large wastewater discharge mentioned in the background technology. In addition, by adopting a three-stage countercurrent spray washing structure combined with an intelligent washing control module and constructing a tiered water use chain from the last stage to the first stage, this invention realizes multi-stage reuse and maximum efficiency enhancement of water resources.

[0078] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pretreatment process for electrostatic spraying of zinc-steel guardrail surfaces, characterized in that, The process includes the following steps: Step S1: The zinc-steel guardrail workpiece is subjected to degreasing and surface conversion coating treatment in sequence; Step S2: Perform multi-stage countercurrent spray water washing on the workpiece treated with the surface conversion film; Step S3: Monitor the cleanliness parameters of the wash water in the last-stage spray washing unit in real time; Step S4: Based on the monitored cleanliness parameters, dynamically control the sewage discharge and water replenishment operations of the last-stage spray washing unit; when the cleanliness parameters are lower than the preset threshold, start the sewage discharge valve to discharge some dirty water, and simultaneously start the water replenishment valve to replenish fresh pure water; when the cleanliness parameters are higher than or equal to the preset threshold, maintain the washing water in the system for recycling.

2. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 1, characterized in that, In step S2, the multi-stage countercurrent spray washing adopts a three-stage washing unit, with the water flow direction opposite to the workpiece travel direction, and fresh pure water is only replenished to the last stage washing unit.

3. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 2, characterized in that, In step S3, the cleanliness parameters include conductivity and turbidity values; the preset thresholds include conductivity thresholds and turbidity thresholds; the monitoring process is achieved through online conductivity sensors and online turbidity sensors installed in the circulation pipeline of the last-stage spray washing unit.

4. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 3, characterized in that, The specific process of dynamic control described in step S4 is as follows: When the detected conductivity value exceeds the first set value or the turbidity value exceeds the second set value, it is determined that the cleanliness parameter is lower than the preset threshold. The PLC controller issues a command to open the drain valve and simultaneously open the water supply valve. The total amount of sewage discharge and water replenishment is 5% to 15% of the total volume of the final stage spray washing unit; When the monitored conductivity and turbidity values ​​both fall below 80% of their respective set values, the PLC controller shuts off the drain valve and the water supply valve.

5. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 4, characterized in that, The dirty water discharged from the last stage spray washing unit is directed to the second stage washing unit as makeup water for the second stage washing unit; the wastewater overflowing from the second stage washing unit is directed to the first stage washing unit as makeup water for the first stage washing unit.

6. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 5, characterized in that, Wastewater discharged from the first-stage washing unit first passes through a precision filtration system to remove solid impurities, and is then directed to the degreasing treatment process as replenishment water for the degreasing tank.

7. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 1, characterized in that, In step S2, each stage of the washing unit is equipped with an independent water pump and circulation pipeline. The washing water is atomized and sprayed through nozzles, and a bag filter is installed on the circulation pipeline.

8. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 1, characterized in that, The surface conversion film treatment is a phosphorus-free nano-ceramic conversion film treatment, and the treatment bath is carried out at room temperature without heating.

9. The pretreatment process for electrostatic spraying of zinc-steel guardrail surface according to claim 1, characterized in that, Before step S1, a pre-washing step is also included, and the wastewater generated from the pre-washing is directly sent to the sewage treatment system.

10. An apparatus for implementing the electrostatic spraying pretreatment process for the energy-saving and environmentally friendly zinc-steel guardrail as described in any one of claims 1 to 9, characterized in that, The device includes: The degreasing tank, the conversion membrane treatment tank, and the multi-stage countercurrent spray washing system are arranged in sequence. The last stage of the multi-stage counter-current spray washing system is connected to an intelligent washing control module. The intelligent water washing control module includes a water quality monitoring unit, a control unit, and an execution unit; The water quality monitoring unit includes an online conductivity sensor and an online turbidity sensor installed on the circulation pipeline of the last-stage water washing unit; The control unit is a programmable logic controller, and its signal input terminal is connected to the online conductivity sensor and the online turbidity sensor. The execution unit includes a drain valve and a water supply valve controlled by the programmable logic controller. The drain valve is installed on the drain pipe of the last-stage water washing unit, and the water supply valve is installed on the fresh pure water pipe leading to the last-stage water washing unit.

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