A slag-free impregnation phosphating method using electrochemical method and its application

Abstract

The present invention relates to the field of phosphating technology, and specifically to a slag-free immersion phosphating method and its application using an electrochemical method. In view of the hazards of phosphating slag produced by traditional immersion phosphating and the shortcomings of existing slag-free or low-slag phosphating research, this process places the raw material wire as the cathode and the inert electrode as the anode in a phosphating tank, and starts a DC power supply when the ferrous ion concentration of the phosphating solution reaches the standard. Through the electrochemical method, the ferrous ions are reduced to elemental iron at the cathode and taken out, thereby reducing the generation of phosphating slag. At the same time, a phosphating solution formula is provided, including multiple components such as phosphoric acid, zinc oxide, nitrate, and the like, and a preparation method thereof. This patent realizes the long-term utilization of the traditional phosphating process, reduces costs, improves economy and environmental protection, and does not affect the quality of the phosphating film and the back-end application. It is easy to operate and applicable.

Description

Technical Field

[0001] The invention relates to the technical field of phosphating, and in particular to a slag-free impregnation phosphating method coordinated by an electrochemical method and an application thereof. Background Art

[0002] As a product of phosphating treatment, phosphating slag has complex and diverse components. It usually contains a large amount of phosphates, volatile organic compounds and heavy metals. Among them, heavy metals such as lead, zinc, and cadmium are difficult to degrade. Once they enter the water and soil environment, they will exist for a long time and cause serious pollution. Phosphates have high solubility and are easily dissolved in water, leading to eutrophication of water bodies, which in turn causes algal blooms, red tides and other phenomena, causing great damage to the aquatic ecosystem. Volatile organic compounds may be harmful to human health and may cause respiratory irritation, asthma and other diseases after inhalation. Based on these hazardous characteristics, phosphating slag is classified as HW17 surface treatment waste in the "National List of Hazardous Wastes". It is toxic and corrosive, its resource utilization process is complex, and the cost of harmless disposal is high.

[0003] The cleaning and slag removal process of traditional immersion phosphating generally adopts a method of precipitation outside the tank, and the specific operation is to establish a phosphating solution precipitation tank outside the tank. During the production process, the phosphating solution in the tank needs to be discharged into the precipitation tank regularly. After a period of precipitation, the upper clear phosphating solution is re-injected into the phosphating tank for recycling, and the phosphating waste residue at the bottom of the precipitation tank is bagged and transported and treated in accordance with the relevant regulations on hazardous waste. Although this treatment method can clean the phosphating slag in the phosphating tank more thoroughly, it has obvious defects. First, the entire process needs to suspend production, which will lead to a decrease in production efficiency and increase production costs. Secondly, the process requires manual operation. The operator may be damaged by harmful substances during contact with the phosphating slag and phosphating solution, which is potentially harmful to human health. In addition, during the treatment process, the phosphating slag still contains a lot of phosphating solution, which cannot be effectively separated from the phosphating slag, which not only causes a waste of resources, but also further increases the treatment cost of the phosphating waste residue.

[0004] In addition, the electrolytic phosphating method is a phosphating method different from the traditional immersion phosphating method. It adopts a unique film-forming principle and can achieve slag-free phosphating. However, this process also faces many problems in practical application. First, the production efficiency of the electrolytic phosphating method is relatively low and cannot meet the needs of large-scale production. Secondly, its production cost is high, including high equipment investment, electrolyte cost, and operation and maintenance cost. Furthermore, the electrolyte is prone to instability, which will affect the quality and stability of the phosphating film. Finally, the phosphating film layer produced by the electrolytic phosphating method is different from the film layer produced by the traditional immersion phosphating method in structure and performance. Its application effect is not good and cannot reach the level of the traditional immersion phosphating method. This also limits the large-scale application of the electrolytic phosphating method, making it unable to effectively impact the market share of traditional immersion phosphating. Summary of the invention

[0005] The present application provides a slag-free immersion phosphating method and its application, which uses an electrochemical method to reduce ferrous ions to elemental iron at the cathode and carry them out, thereby reducing the generation of phosphating slag.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] Provided is a slag-free immersion phosphating method using an electrochemical method, comprising:

[0008] When the concentration of ferrous ions in the phosphating solution reaches a preset threshold, an electrochemical method is used to assist in phosphating;

[0009] Among them, each liter of phosphating solution includes the following raw materials:

[0010] Phosphoric acid 130-150g, zinc oxide 75-90g, nitrate 80-120g, film-forming aid 12-20g, N-octyl pyrrolidone 0.3-0.5g, dodecylphenol polyoxyethylene ether 0.3-0.5g, propylene glycol monomethyl ether 0.1-0.3g;

[0011] During the electrochemical assistance, the cathode current density is set to 5-15·A / dm 2 , power-on time 20-100min.

[0012] Further, the electrochemical assisting method comprises:

[0013] S1. Real-time monitoring of ferrous ion concentration in the phosphating solution during the traditional immersion phosphating production operation;

[0014] S2. When the detected ferrous ion concentration in the phosphating solution reaches a preset threshold, the circuit is connected, the negative electrode of the power supply is connected to the raw material wire coil as the cathode, and the positive electrode of the power supply is connected to the inert plate as the anode;

[0015] S3. Turn on the stirring blade at the bottom of the tank and set the stirring speed;

[0016] S4. Turn on the DC power supply and immerse the raw material coil into the phosphating solution of the phosphating tank;

[0017] S5. After the electrochemical reaction is completed, the raw material coil is lifted and transferred to the pickling tank;

[0018] S6. Repeat step S1.

[0019] Further, in step S3, the stirring speed of the stirring blades at the bottom of the tank is maintained at 100-200 r / min.

[0020] Further, in step S4, the cathode current density is set at 10A / dm 2 , power-on time 60min.

[0021] Furthermore, the nitrate is one or more of calcium nitrate, manganese nitrate and nickel nitrate.

[0022] Furthermore, the film-forming aid is 3-5 g of glycerophosphate, 3-5 g of succinic acid, 3-5 g of citric acid, and 3-5 g of gluconic acid.

[0023] Furthermore, the glycerophosphate is one or more of glycerophosphate, sodium glycerophosphate, magnesium glycerophosphate and other glycerophosphate salts.

[0024] Furthermore, the gluconic acid is one or more of gluconic acid, nickel gluconate, sodium gluconate and other gluconates.

[0025] Further, the preparation method of the phosphating solution is:

[0026] W1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0027] W2. Add zinc oxide, phosphoric acid and nitrate to deionized water and stir until the zinc oxide reaction is complete;

[0028] W3. Lower the temperature to 35-45 ° C, add glycerol phosphate, N-octyl pyrrolidone, and dodecylphenol polyoxyethylene ether, and stir until all the added raw materials are dissolved;

[0029] W4. Add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain electrolytic phosphating solution.

[0030] An application of a slag-free immersion phosphating method using an electrochemical method, using the above-mentioned slag-free immersion phosphating method using an electrochemical method to phosphate a material to form a phosphating film on the surface of the material.

[0031] The beneficial effects of the present invention are:

[0032] 1. With the help of the synergistic effect of the electrochemical method, the amount of iron phosphate phosphating slag generated can be significantly reduced, thus realizing the long-term application of the traditional phosphating method. In this process, there is almost no need to clean the tank and remove the slag, which greatly reduces the treatment cost of the phosphating slag, effectively reduces the environmental burden, and also improves the economy and environmental protection of the traditional phosphating method.

[0033] 2. This method can ensure that the application effect of the phosphating film produced by the traditional phosphating method is not affected on the basis of effectively reducing the generation of phosphating slag, and will not reduce the performance of traditional immersion phosphating products in back-end applications.

[0034] 3. The electrochemical synergistic method is easy to operate and can be easily integrated with the traditional immersion phosphating method. Compared with the electrolytic phosphating method, it does not require large-scale transformation of the existing production line, so it has good applicability and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0036] Figure 1 is a metallographic schematic diagram of Example 1 of the present invention;

[0037] Figure 2 is a metallographic schematic diagram of Example 2 of the present invention;

[0038] Figure 3 is a metallographic schematic diagram of Example 3 of the present invention;

[0039] Figure 4 is a SEM schematic diagram of Example 3 of the present invention;

[0040] Figure 5 Schematic diagram of the metallographic structure of Comparative Example 1 of the present invention;

[0041] Figure 6 is a SEM schematic diagram of Comparative Example 1 of the present invention;

[0042] Figure 7 Schematic diagram of the metallographic structure of Comparative Example 2 of the present invention;

[0043] Figure 8 It is a metallographic schematic diagram of comparative example 3 of the present invention. DETAILED DESCRIPTION

[0044] As used herein, "and / or" includes the term of any and all combinations of one or more associated listed items. The terms used herein are only used to describe specific embodiments and are not intended to limit the present invention. As used herein, the singular forms "a", "an", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It is further understood that "including", when used in this specification, specifies the stated features, integers, steps, operations, elements and / or compositions, but does not exclude the existence or addition of one or more other features, integers, steps, operations, elements, compositions and / or combinations thereof.

[0045] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It is further understood that terms, such as defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant art and are not in an idealized or overly formal sense unless explicitly so defined herein.

[0046] The exemplary invention described herein may appropriately lack any one or more element limitations that are not specifically disclosed herein. Therefore, the terms "comprise", "include", "contain", etc. should be understood broadly and non-restrictively. In addition, the terminology used herein is used as a description, not a limitation, and it is unintentional to use these terminology expressions that do not include any equivalent characteristics, but only describe some of their characteristics, but various modifications are possible within the scope of the present invention according to the rights. Therefore, although the present invention has been specifically disclosed by preferred embodiments and optional features, the modifications disclosed herein to embody the changes of the present invention may be recorded by those skilled in the art, and such modifications and changes will be considered to be within the scope of the present invention.

[0047] The raw materials or reagents used in the embodiments of the present invention and the comparative examples are all purchased from mainstream manufacturers in the market. The manufacturer or concentration is not specified, and they are all analytically pure raw materials or reagents that can be routinely obtained. As long as the expected effect can be achieved, there is no particular restriction. The reaction, stirring and other instruments and equipment used in the present embodiment are all purchased from major manufacturers in the market. As long as the expected effect can be achieved, there is no particular restriction. In the present embodiment, if specific techniques or conditions are not specified, the techniques or conditions described in the literature in this area or according to the product specification are carried out.

[0048] A slag-free impregnation phosphating method using an electrochemical method, comprising:

[0049] S1. Real-time monitoring of ferrous ion concentration in the phosphating solution during the traditional immersion phosphating production operation;

[0050] S2. When the detected ferrous ion concentration in the phosphating solution reaches a preset threshold, the circuit is connected, the negative electrode of the power supply is connected to the raw material wire coil as the cathode, and the positive electrode of the power supply is connected to the inert plate as the anode;

[0051] S3. Turn on the stirring blade at the bottom of the tank and set the stirring speed;

[0052] S4. Turn on the DC power supply and immerse the raw material coil into the phosphating solution of the phosphating tank;

[0053] S5. After the electrochemical reaction is completed, the raw material coil is lifted and transferred to the pickling tank;

[0054] S6. Repeat step S1;

[0055] Wherein, through steps S1-S5, when the ferrous ion concentration of the phosphating solution reaches a preset threshold value, the negative electrode of the power supply is connected to the raw material wire coil (cathode), the positive electrode of the power supply is connected to the inert electrode plate (anode), the DC power supply is started, and the bottom stirring of the tank is turned on to eliminate concentration polarization. The set threshold value of the ferrous ion concentration is set to 0.5 mol / L.

[0056] In the phosphating tank, an electrochemical reaction occurs on the surface of the raw wire coil immersed in the phosphating solution. The ferrous ions gain electrons and turn into iron, which is deposited on the surface of the coil. The hydrogen ions gain electrons and are reduced to hydrogen, which is desorbed on the surface of the cathode wire. On the surface of the inert plate immersed in the phosphating solution, water molecules lose electrons, forming oxygen that desorbs from the surface of the inert plate. The released hydrogen ions return to the phosphating solution to replenish the free acid consumed in the normal phosphating process.

[0057] After the deposition is completed, turn off the power supply, disconnect the cathode and anode from the power supply, return the deposited raw wire coil to the pickling tank, and carry out normal production according to the traditional immersion phosphating process. The elemental iron deposited on the wire is removed during pickling, which does not affect the subsequent phosphating process. The phosphating film layer at this time is no different from the phosphating film layer during normal production.

[0058] Finally, step S1 is repeated to continue monitoring the change in the concentration of ferrous ions in the phosphating solution.

[0059] In addition, it should be noted that each liter of phosphating solution includes the following raw materials:

[0060] Phosphoric acid 130-150g, zinc oxide 75-90g, nitrate 80-120g, film-forming aid 12-20g, N-octyl pyrrolidone 0.3-0.5g, dodecylphenol polyoxyethylene ether 0.3-0.5g, propylene glycol monomethyl ether 0.1-0.3g.

[0061] Among them, the film-forming agent is: 3-5g of glycerophosphate, 3-5g of succinic acid, 3-5g of citric acid, and 3-5g of gluconic acid.

[0062] in,

[0063] Phosphoric acid (CAS#: 7664-38-2); Zinc oxide (CAS#: 1314-13-2); N-octyl pyrrolidone (CAS#: 2687-94-7); Dodecylphenol polyoxyethylene ether (CAS#: 9041-29-6); Propylene glycol monomethyl ether (CAS#: 1320-67-8); Calcium nitrate (CAS#: 35054-52-5); Manganese nitrate (CAS#: 17141-63-8); Nickel nitrate (CAS#: 14216-75- 2); succinic acid (CAS#: 110-15-6), citric acid (CAS#: 5949-29-1); glycerophosphate (CAS#: 57-03-4); sodium glycerophosphate (CAS#: 89923-83-1); magnesium glycerophosphate (CAS#: 927-20-8); gluconic acid (CAS#: 526-95-4); nickel gluconate (CAS#: 71957-07-8); sodium gluconate (CAS#: 41859-67-0).

[0064] Glycerol phosphate is hydrophilic, can increase the viscosity and surface activity of the solution, can form complexes with metal ions, help form a uniform phosphating film, and improve the corrosion resistance of the film. In addition, when used in conjunction with the electrochemical method, glycerol phosphate can affect the adsorption and diffusion process of metal ions on the electrode surface, change the charge state and reaction kinetics of the electrode surface, and promote the reduction deposition of iron ions on the wire.

[0065] Citric acid can complex the metal cations in the phosphating solution and exist in the phosphating solution in a dissolved state, thereby preventing the effective components from being precipitated.

[0066] Succinic acid can enhance the binding force of the phosphating film. The carboxyl functional groups in succinic acid can form stable chemical bonds with active sites on the surface of the metal substrate (such as oxides, hydroxyls, etc.). These chemical bonds can enhance the interfacial adhesion between the phosphating film and the substrate, and improve the adhesion and corrosion resistance of the phosphating film. In addition, when used in conjunction with the electrochemical method, the carboxyl functional groups in succinic acid can increase surface activity and reduce surface tension, thereby improving the wettability of the phosphating solution to the workpiece surface and facilitating the uniform reduction and deposition of iron ions on the workpiece surface.

[0067] At the same time, the combination of succinic acid and citric acid can have a good buffering effect on the free acid of the phosphating solution and can be used to adjust the acidity of the phosphating solution. The control of acidity is crucial to the uniformity and quality of the film. The combination of succinic acid and citric acid can help improve the microstructure of the phosphating film, reduce pores and cracks, and thus improve the appearance quality.

[0068] Gluconic acid can promote the formation of phosphating film and improve the corrosion resistance of the film. Gluconate ions can form stable complexes with metal ions. This complexation helps metal ions to exist stably in the solution and be evenly distributed on the metal surface, which is conducive to the formation of phosphating film. Gluconic acid can also promote the adsorption of phosphate on the metal surface, which is conducive to the formation of a uniform and dense phosphating film.

[0069] N-octyl pyrrolidone, as a surfactant, is used in combination with the non-ionic surfactant dodecylphenol polyoxyethylene ether to reduce surface tension, promote the adsorption of phosphate on the metal surface, and is conducive to the formation of a uniform and dense phosphating film layer.

[0070] In the present application, propylene glycol monomethyl ether is used as a solubilizer to reduce the aggregation and precipitation of organic matter in the solution, thereby maintaining the uniformity and stability of the solution. It helps to disperse and dissolve organic matter in water, improve the solubility of organic matter in the formula, and stabilize the phosphating solution system.

[0071] The preparation method of the phosphating solution comprises the following steps:

[0072] W1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0073] W2. Add zinc oxide, phosphoric acid and nitrate to deionized water and stir until the zinc oxide reaction is complete;

[0074] W3. Lower the temperature to 35-45 ° C, add glycerol phosphate, N-octyl pyrrolidone, and dodecylphenol polyoxyethylene ether, and stir until all the added raw materials are dissolved;

[0075] W4. Add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain electrolytic phosphating solution.

[0076] Preferably, in step W2, the temperature is maintained at 80-90°C.

[0077] Preferably, in step W3, the temperature is maintained at 45°C.

[0078] Preferably, in step W2, the stirring speed during the stirring and dissolving process is maintained at 100-200 r / min.

[0079] Preferably, in step W3, the stirring speed during the stirring and dissolving process is maintained at 80-160 r / min.

[0080] The phosphating solution does not contain traditional oxidants, and the divalent iron ions are regulated by electrochemical methods. The cathode is connected to the raw material wire, the anode is connected to the inert plate, and is placed in the phosphating tank. When the concentration of divalent iron ions in the phosphating solution is too high, the electrochemical reaction reduces the divalent iron ions to elemental iron on the cathode and deposits on the wire, and the anode produces oxygen and releases hydrogen ions to maintain the free acidity of the phosphating solution. The phosphating solution formula is optimized to adapt to the electrochemical treatment and ensure the quality of the phosphating film. The wire with elemental iron deposited returns to the previous pickling tank, removes iron in the pickling step, avoids the formation of phosphating slag, and maintains the composition balance of the phosphating solution. The configuration system of the present invention is simple, and the electrochemical treatment is started only when needed. It is usually consistent with the traditional immersion phosphating process, and no complicated changes are required. It not only avoids the steps of frequent tank cleaning and slag removal required for traditional immersion phosphating, reduces the generation of phosphating slag, but also improves the quality of the phosphating film, and improves the environmental protection and economic benefits of the traditional immersion phosphating process.

[0081] According to the above-mentioned slag-free immersion phosphating method using electrochemical method, phosphating solution, and preparation method of phosphating solution, the following embodiments are provided:

[0082] Example 1

[0083] A slag-free impregnation phosphating method using an electrochemical method, wherein the current density is set to 15A / dm 2 , the power-on time is set to 100 minutes, the phosphating temperature is 50°C, and the phosphating time is 15 minutes.

[0084] Each liter of the above phosphating solution includes the following raw materials:

[0085] Phosphoric acid 150g, zinc oxide 90g, calcium nitrate 120g, sodium glycerophosphate 5g, succinic acid 5g, citric acid 5g, sodium gluconate 5g, methacrylate 5g, N-octyl pyrrolidone 0.5g, dodecylphenol polyoxyethylene ether 0.5g, propylene glycol monomethyl ether 0.3g, and deionized water as the balance.

[0086] The preparation method of the above-mentioned phosphating solution comprises the following steps:

[0087] S1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0088] S2. Add zinc oxide, phosphoric acid and nitrate to deionized water, raise the temperature to 80°C, stir thoroughly until the zinc oxide reaction is complete, and maintain the stirring speed at 200r / min during the stirring and dissolving process;

[0089] S3. Lower the temperature to 45 ° C, add glycerol phosphate, N-octyl pyrrolidone, dodecylphenol polyoxyethylene ether, stir until the added raw materials are completely dissolved, and maintain the stirring speed at 160r / min during the stirring and dissolving process;

[0090] S4. Then add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain an electrolytic phosphating solution.

[0091] Example 2

[0092] A slag-free impregnation phosphating method using an electrochemical method, wherein the current density is set to 5A / dm 2 , the power-on time is set to 20 minutes, the phosphating temperature is 35°C, and the phosphating time is 7 minutes.

[0093] Each liter of the above phosphating solution includes the following raw materials:

[0094] Phosphoric acid 130g, zinc oxide 75g, nitrate (calcium nitrate 70g, nickel nitrate 10g) 80g, glycerophosphate 3g, succinic acid 3g, citric acid 3g, gluconic acid 3g, N-octyl pyrrolidone 0.3g, dodecylphenol polyoxyethylene ether 0.3g, propylene glycol monomethyl ether 0.2g, and deionized water as the balance.

[0095] The preparation method of the above-mentioned phosphating solution comprises the following steps:

[0096] S1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0097] S2. Add zinc oxide, phosphoric acid and nitrate to deionized water, raise the temperature to 90°C, stir thoroughly until the zinc oxide reaction is complete, and maintain the stirring speed at 100 r / min during the stirring and dissolving process;

[0098] S3. Lower the temperature to 35 ° C, add glycerol phosphate, N-octyl pyrrolidone, dodecylphenol polyoxyethylene ether, stir until all the added raw materials are dissolved, and maintain the stirring speed at 80r / min during the stirring and dissolving process;

[0099] S4. Then add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain an electrolytic phosphating solution.

[0100] Example 3

[0101] A slag-free impregnation phosphating method using an electrochemical method, wherein the current density is set to 15A / dm 2 , the power-on time is set to 100 minutes, the phosphating temperature is 50°C, and the phosphating time is 15 minutes.

[0102] Each liter of the above phosphating solution includes the following raw materials:

[0103] Phosphoric acid 130g, zinc oxide 75g, nitrate (calcium nitrate 70g, nickel nitrate 10g) 80g, glycerophosphate 3g, succinic acid 3g, citric acid 3g, gluconic acid 3g, N-octyl pyrrolidone 0.3g, dodecylphenol polyoxyethylene ether 0.3g, propylene glycol monomethyl ether 0.2g, and deionized water as the balance.

[0104] The preparation method of the above-mentioned phosphating solution comprises the following steps:

[0105] S1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0106] S2. Add zinc oxide, phosphoric acid and nitrate to deionized water, raise the temperature to 90°C, stir thoroughly until the zinc oxide reaction is complete, and maintain the stirring speed at 100 r / min during the stirring and dissolving process;

[0107] S3. Lower the temperature to 35 ° C, add glycerol phosphate, N-octyl pyrrolidone, dodecylphenol polyoxyethylene ether, stir until all the added raw materials are dissolved, and maintain the stirring speed at 80r / min during the stirring and dissolving process;

[0108] S4. Then add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain an electrolytic phosphating solution.

[0109] Example 4

[0110] A slag-free impregnation phosphating method using an electrochemical method, wherein the current density is set to 5A / dm 2 , the power-on time is set to 20 minutes, the phosphating temperature is 35°C, and the phosphating time is 7 minutes.

[0111] Each liter of the above phosphating solution includes the following raw materials:

[0112] Phosphoric acid 150g, zinc oxide 90g, calcium nitrate 120g, sodium glycerophosphate 5g, succinic acid 5g, citric acid 5g, sodium gluconate 5g, methacrylate 5g, N-octyl pyrrolidone 0.5g, dodecylphenol polyoxyethylene ether 0.5g, propylene glycol monomethyl ether 0.3g, and deionized water as the balance.

[0113] The preparation method of the above-mentioned phosphating solution comprises the following steps:

[0114] S1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0115] S2. Add zinc oxide, phosphoric acid and nitrate to deionized water, raise the temperature to 80°C, stir thoroughly until the zinc oxide reaction is complete, and maintain the stirring speed at 200r / min during the stirring and dissolving process;

[0116] S3. Lower the temperature to 45 ° C, add glycerol phosphate, N-octyl pyrrolidone, dodecylphenol polyoxyethylene ether, stir until the added raw materials are completely dissolved, and maintain the stirring speed at 160r / min during the stirring and dissolving process;

[0117] S4. Then add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain an electrolytic phosphating solution.

[0118] Example 5

[0119] A slag-free impregnation phosphating method using an electrochemical method, wherein the current density is set to 10A / dm 2 , the power-on time is set to 60 minutes, the phosphating temperature is 40°C, and the phosphating time is 8 minutes.

[0120] Each liter of the above phosphating solution includes the following raw materials:

[0121] Phosphoric acid 140g, zinc oxide 80g, nitrate (calcium nitrate 80g, nickel nitrate 20g) 100g, glycerophosphate 4g, succinic acid 4g, citric acid 4g, gluconic acid 4g, N-octyl pyrrolidone 0.4g, dodecylphenol polyoxyethylene ether 0.4g, propylene glycol monomethyl ether 0.2g, and deionized water as the balance.

[0122] The preparation method of the above-mentioned phosphating solution comprises the following steps:

[0123] S1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution;

[0124] S2. Add zinc oxide, phosphoric acid and nitrate to deionized water, raise the temperature to 85°C, stir thoroughly until the zinc oxide reaction is complete, and maintain the stirring speed at 150r / min during the stirring and dissolving process;

[0125] S3. Lower the temperature to 40 ° C, add glycerol phosphate, N-octyl pyrrolidone, dodecylphenol polyoxyethylene ether, stir until all the added raw materials are dissolved, and maintain the stirring speed at 120r / min during the stirring and dissolving process;

[0126] S4. Then add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain an electrolytic phosphating solution.

[0127] Comparative Example 1

[0128] A phosphating solution, without adding glycerophosphate, succinic acid, citric acid, and gluconic acid, and other conditions are consistent with those in Example 3.

[0129] Comparative Example 2

[0130] A phosphating solution, when used in conjunction with the electrochemical method, the current density is set to 30A / dm 2 , the power-on time is set to 200 min, and the other conditions are consistent with Example 3.

[0131] Comparative Example 3

[0132] A phosphating solution, when used in conjunction with the electrochemical method, the current density is set to 0.3A / dm 2 , the power-on time is set to 1 min, and the other conditions are consistent with Example 3.

[0133] The phosphating solutions prepared in the above Examples 1-5 and Comparative Example 1 are applied to the phosphating process;

[0134] The specific phosphating process is: pickling → water washing → phosphating → water washing → drying;

[0135] Among them, the experimental material is 130mm*20mm*3mm Q235 steel plate, and the phosphating method is immersion;

[0136] After phosphating 50 pieces of Q235 steel plates, the electrochemical method was started to reduce and deposit the iron ions in the phosphating solution.

[0137] According to the requirements of each embodiment and comparative example, an electrochemical method is used for immersion phosphating. After phosphating 50 Q235 steel sheets, iron reduction deposition is performed in the phosphating tank. A total of 200 Q235 steel sheets are continuously phosphated, and the corresponding current density is applied for the corresponding time.

[0138] ICP was used to monitor the iron ion concentration in the phosphating solution before each reduction deposition, and the dry weight of the sediment produced during the phosphating process was monitored (phosphating slag dry weight: after the phosphating solution was fully stirred, it was filtered, and the filter residue was taken and dried at 110°C for 5 hours and then weighed). The data are summarized in Table 1.

[0139] Table 1. Phosphating slag weight of implementation examples 1-5 and comparative examples 1-3

[0140]

[0141]

[0142] It can be seen from the above results that after phosphating 50 Q235 steel plates in the embodiment, the increase of iron in the phosphating solution is significantly lower than that in comparative examples 1 and 2, and the amount of phosphating slag generated is also significantly lower than that in the three comparative examples.

[0143] Compared with Example 3, no film-forming aids such as glycerophosphate, succinic acid, citric acid, and gluconic acid were added to the phosphating solution formula of Comparative Example 1. From the results, it can be seen that the dry weight of the phosphating slag in Comparative Example 1 after phosphating 200 Q235 steel plates reached 4.55 g, which is much higher than the level of the embodiment. This shows that the addition of film-forming aids such as glycerophosphate, succinic acid, citric acid, and gluconic acid can significantly reduce the generation of phosphating slag, and these film-forming aids can promote the reduction and deposition of iron ions at the cathode, reduce its concentration in the phosphating solution, and thus reduce the generation of phosphating slag.

[0144] Compared with Example 3, the current density of Comparative Example 2 is 30A / dm 2 , the power-on time is 200min, which is much higher than 15A / dm in Example 3 2 and 100min. The dry weight of the phosphating slag of Comparative Example 2 is 4.15g, which is higher than that of Example 3, indicating that this higher current density and extended power-on time, although helpful to the reduction of iron ions to a certain extent, bring about adverse effects. Excessive current density and power-on time can cause the chemical reaction in the phosphating solution to change. When the iron ions are fully reduced, continuing to energize will cause the hydrogen ions in the cathode region to be reduced to generate hydrogen. This process consumes hydrogen ions, so that the concentration of hydrogen ions near the cathode is reduced, and then promotes the ionization of dihydrogen phosphate ions, releasing hydrogen ions and phosphate ions. In this process, the concentration of zinc ions and phosphate ions in the phosphating solution gradually increases until the saturation point is reached. At this time, zinc ions and phosphate ions combine to form zinc phosphate precipitation, and these precipitates are another type of phosphating slag except iron phosphate, which eventually settles to the bottom of the phosphating tank. This not only does not improve the phosphating efficiency, but also causes a waste of the phosphating solution, and the formation of precipitation means that the effective ingredients in the phosphating solution are consumed.

[0145] Compared with Example 3, the current density of Comparative Example 3 is 0.3A / dm 2 The power-on time is 1 min, which is much lower than 15A / dm in Example 3. 2 and 100min. When the current density is low and the power-on time is short, the efficiency of the electrochemical reaction is not enough to fully reduce the iron ions, resulting in a continuous increase in the iron ion concentration in the phosphating solution and the inability to inhibit the formation of phosphating slag.

[0146] The technical indicators of the phosphated film layer of the 200th Q235 steel plate phosphated in Examples 1-5, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were tested, and the test results are shown in Table 2;

[0147] The specific detection methods or detection conditions are:

[0148] ① Adhesion, according to GB / T 1720-2020 paint film circle test

[0149] ②Corrosion resistance, copper sulfate pitting test, drop the pitting solution on the sample and observe the time when the red corrosion spot appears. The pitting solution is: 41g copper sulfate pentahydrate, 35g sodium chloride, 13mL 0.1mol / L hydrochloric acid, and dilute to 1L with distilled water.

[0150] ③ Soak in sodium chloride solution: immerse the phosphating sample (at room temperature) in a 3% sodium chloride aqueous solution, keep it at room temperature for a specified time, and visually inspect whether there is any rust on the phosphating surface.

[0151] ④ For indoor rust prevention, the dried test pieces should be stored at room temperature with a relative humidity not exceeding 70% and no corrosive gases, and the storage time should be recorded.

[0152] Table 2. Technical indicators of phosphating films of implementation examples 1-5 and comparative examples 1-3

[0153]

[0154]

[0155] As can be seen from Table 2, when the 200th Q235 steel plate was phosphated, the phosphating film layer of Examples 1-5 had good performance, the film layer was uniform and dense, and was superior to the phosphating film layer of Comparative Examples 1-3 in terms of thickness, adhesion, corrosion resistance, etc. This shows that the phosphating film layer of Examples 1-5 had good quality and could meet the requirements of the phosphating process. In Comparative Examples 1-3, due to the unreasonable setting of the phosphating solution formula and process parameters, when the 200th Q235 steel plate was phosphated, the formula and process of the comparative example had affected the uniformity and density of the phosphating film layer, thereby reducing the adhesion and corrosion resistance of the phosphating film layer. The above results show that the slag-free immersion phosphating method coordinated with the electrochemical method in the embodiment can effectively improve the overall performance of the phosphating film layer, making it have significant advantages in film weight, bonding strength and anti-corrosion protection.

[0156] According to the requirements of each embodiment and comparative example, an electrochemical method coordinated immersion phosphating operation was performed, and the effect of the phosphating film layer of the 200th Q235 steel plate phosphated in embodiments 1-3, comparative example 1, comparative example 2, and comparative example 3 was observed by metallographic microscope, and the effect of the phosphating film layer of the 200th Q235 steel plate phosphated in embodiment 3 and comparative example 1 was observed by SEM. The metallographic photos and SEM photos are shown in Figure 1-8 .

[0157] Reference Figure 1-4The metallographic photographs of Examples 1-3 and the SEM photograph of Example 3 show that the phosphated film layer exhibits a high degree of uniformity and integrity. The film layer has no obvious pores or defects, indicating that the phosphate can be uniformly deposited on the surface of the substrate to form a dense protective film. It effectively covers the entire surface of the substrate, exhibits excellent protective properties, can resist erosion from the external environment, and ensures the long-term durability of the steel plate.

[0158] Reference Figure 5 , 6 The metallographic and SEM photos of Comparative Example 1 show that the quality of the film is relatively poor. Since the iron content in the phosphating bath is not effectively controlled, the surface of the film is rough and there are uneven deposits. These rough areas may become the starting point of corrosion, reducing the overall corrosion resistance. In addition, the coverage of the film is not complete, and insufficient protection may occur in some areas.

[0159] Reference Figure 7 The metallographic photograph of Comparative Example 2 shows that almost no obvious phosphating film layer is observed, and a large amount of substrate is directly exposed. This indicates that the proportion of effective components in the phosphating bath is seriously out of control, resulting in the inability to form an effective phosphating film on the substrate surface.

[0160] Reference Figure 8 The metallographic photograph of Comparative Example 3 shows that although the film layer is formed, the effect is general. In the photo, a large amount of phosphating slag is deposited on the film layer, which not only affects the uniformity of the film layer, but also may block the active sites in the phosphating process and reduce the phosphating efficiency. Excessive presence of phosphating slag may also lead to incomplete coverage of the film layer, increasing the risk of corrosion of the substrate.

[0161] The above description is only a specific embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformation made by the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. A slag-free impregnation phosphating method using an electrochemical method, characterized in that: include: When the concentration of ferrous ions in the phosphating solution reaches a preset threshold, an electrochemical method is used to assist in phosphating; Among them, each liter of phosphating solution includes the following raw materials: Phosphoric acid 130-150g, zinc oxide 75-90g, nitrate 80-120g, film-forming aid 12-20g, N-octyl pyrrolidone 0.3-0.5g, dodecylphenol polyoxyethylene ether 0.3-0.5g, propylene glycol monomethyl ether 0.1-0.3g; During the electrochemical assistance, the cathode current density is set to 5-15·A / dm 2 Power-on time 20-100min.

2. The slag-free impregnation phosphating method using electrochemical method according to claim 1 is characterized in that: The electrochemical assisting method comprises: S1. Real-time monitoring of ferrous ion concentration in the phosphating solution during the traditional immersion phosphating production operation; S2. When the detected ferrous ion concentration in the phosphating solution reaches a preset threshold, the circuit is connected, the negative electrode of the power supply is connected to the raw material wire coil as the cathode, and the positive electrode of the power supply is connected to the inert plate as the anode; S3. Turn on the stirring blade at the bottom of the tank and set the stirring speed; S4. Turn on the DC power supply and immerse the raw material coil into the phosphating solution of the phosphating tank; S5. After the electrochemical reaction is completed, the raw material coil is lifted and transferred to the pickling tank; S6. Repeat step S1.

3. The slag-free impregnation phosphating method using electrochemical method according to claim 2 is characterized in that: In step S3, the stirring speed of the stirring blades at the bottom of the tank is maintained at 100-200 r / min.

4. The slag-free impregnation phosphating method using electrochemical method according to claim 2 is characterized in that: In step S4, the cathode current density is set at 10 A / dm 2 , power-on time 60min.

5. The slag-free impregnation phosphating method using electrochemical method according to claim 1 is characterized in that: The nitrate is one or more of calcium nitrate, manganese nitrate and nickel nitrate.

6. The slag-free immersion phosphating method using electrochemical method according to claim 1 is characterized in that: The film-forming aids are 3-5 g of glycerophosphate, 3-5 g of succinic acid, 3-5 g of citric acid, and 3-5 g of gluconic acid.

7. The slag-free impregnation phosphating method using electrochemical method according to claim 6 is characterized in that: The glycerophosphate is one or more of glycerophosphate, sodium glycerophosphate, magnesium glycerophosphate and other glycerophosphate salts.

8. The slag-free immersion phosphating method using electrochemical method according to claim 6, characterized in that: The gluconic acid is one or more of gluconic acid, nickel gluconate, sodium gluconate and other gluconates.

9. The slag-free immersion phosphating method using electrochemical method according to claim 1, characterized in that: The preparation method of the phosphating solution is: W1. Prepare the materials according to the weight of the corresponding raw materials per liter of phosphating solution; W2. Add zinc oxide, phosphoric acid and nitrate to deionized water and stir until the zinc oxide reaction is complete; W3. Lower the temperature to 35-45 ° C, add glycerol phosphate, N-octyl pyrrolidone, and dodecylphenol polyoxyethylene ether, and stir until all the added raw materials are dissolved; W4. Add succinic acid, citric acid, gluconic acid and propylene glycol monomethyl ether and stir until dissolved, then cool to room temperature to obtain electrolytic phosphating solution.

10. An application of a slag-free impregnation phosphating method using an electrochemical method, characterized in that: The material is phosphated by the slag-free immersion phosphating method coordinated with the electrochemical method according to any one of claims 1 to 9 to form a phosphating film on the surface of the material.

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