Deplating solution and application thereof

Abstract

The invention provides a deplating solution and application thereof, and belongs to the technical field of metal surface treatment. The stripping solution provided by the invention comprises the following components: organic phosphonic acid, fluoride, an organic corrosion inhibitor and water, the molecular structure of the organic phosphonic acid has a plurality of phosphate groups, the organic phosphonic acid, zinc ions and nickel ions can form an extremely stable complex with good water solubility, and plating metal ions are stripped from the surface of a workpiece and stabilized in the solution; fluorine ions have extremely small ion radius and strong coordination capability, and can preferentially adsorb and penetrate through an oxidation film to react with metal oxides in the oxidation film to generate a soluble fluorine-oxygen complex, and a fresh metal layer is exposed to be complexed and dissolved by organic phosphonic acid; the core function of the organic corrosion inhibitor is selective adsorption and protection, and the organic corrosion inhibitor can be preferentially adsorbed on active points of an exposed matrix to form a layer of compact monomolecular protective film, so that the corrosion reaction of the stripping solution to the matrix is inhibited; and meanwhile, the deplating solution is green and environment-friendly.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, specifically relating to a stripping solution and its application. Background Technology

[0002] Electroplated zinc and zinc-nickel alloy coatings are widely used for the protection of steel components. However, during the production process of electroplating zinc and zinc-nickel alloys, it is inevitable that defective coated parts will be produced due to improper control of process parameters, equipment failure, or human error. In order to save costs and recover the base material, it is necessary to remove the defective coatings and re-electroplating. Therefore, efficient and environmentally friendly stripping technology is an indispensable part of the electroplating industry.

[0003] Traditional stripping processes typically use strong acids such as concentrated hydrochloric acid and concentrated nitric acid, or strong alkaline systems combining sodium hydroxide with oxidants (such as sodium nitrate) as stripping solutions. While these solutions offer relatively fast stripping rates, they have several drawbacks: First, strong acids and alkalis are highly corrosive and volatile, causing significant damage to production equipment and posing a threat to the health and safety of operators. Second, the stripping process generates large amounts of toxic and harmful gases such as nitrogen oxides and chlorine, as well as waste liquid with high concentrations of heavy metal ions, resulting in severe environmental pollution and high costs for subsequent waste treatment. Third, traditional strong acid and strong alkali stripping solutions cause severe over-corrosion of the substrate, easily leading to changes in part dimensions, surface over-corrosion, or even scrapping, posing a significant potential risk to ultra-high-strength components used in aerospace applications.

[0004] Therefore, developing a highly efficient and environmentally friendly stripping solution has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a stripping solution and its application. The stripping solution provided by this invention does not contain strong acids, strong alkalis, or heavy metal oxidants. While achieving efficient stripping, it significantly reduces or minimizes corrosion to the substrate and reduces the generation of toxic and harmful substances, making it environmentally friendly.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: The present invention provides a stripping solution comprising the following components: organophosphonic acid, fluoride, organic corrosion inhibitor and water.

[0007] Preferably, the organophosphonic acid includes one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, and ethylenediaminetetramethylenephosphonic acid.

[0008] Preferably, the concentration of organophosphonic acid in the stripping solution is 0.1~0.4 mol / L.

[0009] Preferably, the fluoride includes one or more of sodium fluoride, potassium fluoride, and ammonium bifluoride.

[0010] Preferably, the concentration of fluoride in the stripping solution is 2.5~10 g / L.

[0011] Preferably, the organic corrosion inhibitor includes one or more of thiourea, benzotriazole, and methylbenzotriazole.

[0012] Preferably, the concentration of the organic corrosion inhibitor in the stripping solution is 0.2~1g / L.

[0013] The present invention also provides the application of the stripping solution described above in the removal of zinc and / or zinc-nickel plating.

[0014] Preferably, the workpiece containing zinc plating and / or zinc-nickel plating is immersed in a stripping solution for stripping to obtain the stripped workpiece.

[0015] Preferably, the temperature for stripping is 20~60℃.

[0016] This invention provides a stripping solution comprising the following components: organophosphonic acid, fluoride, organic corrosion inhibitor, and water. The organophosphonic acid in the stripping solution is the core component. Its molecular structure contains multiple phosphate groups, enabling it to form extremely stable, water-soluble complexes with zinc and nickel ions. This strong complexing action effectively strips the plating metal ions from the workpiece surface and stabilizes them in the solution, thereby continuously promoting the plating dissolution reaction. Compared to the severe corrosion method of traditional strong acids relying on high concentrations of hydrogen ions, the effect of organophosphonic acid is gentler, avoiding the release of large amounts of hydrogen gas and hydrogen embrittlement damage to the substrate. The fluoride mainly plays a role in activating the surface and accelerating the initial reaction, especially for zinc-nickel alloy plating. Fluoride ions have extremely small ionic radii and strong coordination capabilities, enabling them to preferentially adsorb and penetrate the oxide film to react with the metal oxides therein, generating soluble fluoride-oxygen complexes. This disrupts the integrity of the passivation film, exposing fresh metal. The metal layer is used for complexation and dissolution by organophosphonic acids. The rapid and uniform removal of zinc and zinc-nickel platings is achieved through the synergistic effect of organophosphonic acids and fluorides. The core function of the organic corrosion inhibitor is selective adsorption and protection. The inhibitor molecules can preferentially adsorb on the active sites of the exposed substrate, forming a dense monomolecular protective film. This effectively blocks the contact between the stripping solution and the substrate, significantly increases the hydrogen evolution overpotential, and thus significantly inhibits the corrosion reaction of the stripping solution on the substrate. However, the adsorption of zinc and zinc-nickel alloy platings by this protective film is weak or unstable. Therefore, the stripping reaction can still proceed smoothly. This selective inhibition mechanism ensures that the substrate is protected with almost "zero damage" while efficiently removing the plating. At the same time, the stripping solution is green and environmentally friendly, with no volatile strong acids, no toxic gases, and no heavy metal oxidants. The production environment is safe and the wastewater treatment is simple. Attached Figure Description

[0017] Figure 1The metallographic structure of the Q235 steel workpiece in Application Example 1 is shown below. Figure 2 The X-ray analysis results of the Q235 steel workpiece with zinc coating in Example 1 are shown. Figure 3 The metallographic structure of the workpiece after plating removal in Application Example 1; Figure 4 The X-ray analysis results of the workpiece after plating removal in Example 1 are used; Figure 5 For comparison, the metallographic structure of the workpiece after plating removal in Application Example 1; Figure 6 To compare the X-ray analysis results of the workpiece after plating removal in Application Example 1; Figure 7 Metallographic structure of the 30CrMnSiA high-strength steel workpiece in Application Example 2; Figure 8 The X-ray analysis results of the 30CrMnSiA high-strength steel workpiece with zinc coating in Example 2 are shown. Figure 9 The metallographic structure of the workpiece after plating removal in Application Example 2; Figure 10 The X-ray analysis results of the workpiece after plating removal in Example 2 are used; Figure 11 To compare the X-ray analysis results of the workpiece in Application Example 2 after stripping at 40°C for 40 minutes; Figure 12 For comparison, the metallographic structure of the workpiece in Application Example 2 after being stripped at 40°C for 40 minutes and then stripped at 60°C for 40 minutes is shown in the image. Figure 13 To compare the X-ray analysis results of the workpiece in Application Example 2 after it was stripped at 40°C for 40 min and then stripped at 60°C for 40 min; Figure 14 The X-ray analysis results of the Q235 steel workpiece with zinc-nickel alloy coating in Example 4 are used. Figure 15 The metallographic structure of the workpiece after plating removal in Example 4; Figure 16 The X-ray analysis results of the workpiece after plating removal in Example 4 are used; Figure 17 For comparison, see the metallographic structure of the workpiece after plating removal in Application Example 3; Figure 18 To compare the X-ray analysis results of the workpiece after plating removal in Application Example 3; Figure 19 To compare the X-ray analysis results of the workpiece after deplating in Application Example 4. Detailed Implementation

[0018] The present invention provides a stripping solution comprising the following components: organophosphonic acid, fluoride, organic corrosion inhibitor and water.

[0019] Unless otherwise specified, the present invention does not have any special limitations on the source of each component, and commercially available products well known to those skilled in the art can be used.

[0020] The stripping solution provided by this invention includes organophosphonic acid.

[0021] In this invention, the organophosphonic acid preferably includes one or more of hydroxyethylidene diphosphonic acid (HEDP), aminotrimethylenephosphonic acid (ATMP), and ethylenediaminetetramethylenephosphonic acid (EDTMP).

[0022] In this invention, the concentration of organophosphonic acid in the stripping solution is preferably 0.1~0.4 mol / L. As one embodiment, the concentration of organophosphonic acid in the stripping solution can specifically be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, or 0.4 mol / L.

[0023] In this invention, the organophosphonic acid is the core component. Its molecular structure contains multiple phosphate groups, enabling it to form extremely stable, water-soluble complexes with zinc and nickel ions. This powerful complexation effectively strips the plating metal ions from the workpiece surface and stabilizes them in the solution, thereby continuously promoting the plating dissolution reaction. Compared to the severe corrosion method of traditional strong acids relying on high concentrations of hydrogen ions, the effect of organophosphonic acid is gentler, avoiding the release of large amounts of hydrogen gas and hydrogen embrittlement damage to the substrate. By controlling the type and concentration of organophosphonic acid within the aforementioned range, this invention further improves the stripping effect.

[0024] The stripping solution provided by this invention also includes fluorides.

[0025] In this invention, the fluoride preferably includes one or more of sodium fluoride, potassium fluoride, and ammonium bifluoride.

[0026] In this invention, the concentration of fluoride in the stripping solution is preferably 2.5~10 g / L. As one embodiment, the concentration of fluoride in the stripping solution can specifically be 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, or 10 g / L.

[0027] In this invention, the fluoride mainly serves to activate the surface and accelerate the initial reaction, especially for zinc-nickel alloy coatings. Fluoride ions have extremely small ionic radii and strong coordination capabilities, enabling them to preferentially adsorb and penetrate the oxide film to react with the metal oxides therein, forming soluble fluoride-oxygen complexes (such as ZnF4). 2- NiF6 4- (etc.), thereby disrupting the integrity of the passivation film and exposing a fresh metal layer for complexation and dissolution by organophosphonic acids. The synergistic effect of organophosphonic acids and fluorides achieves rapid and uniform removal of zinc and zinc-nickel plating. This invention controls the type and concentration of fluorides within the aforementioned range, further improving the stripping effect.

[0028] The stripping solution provided by this invention also includes an organic corrosion inhibitor.

[0029] In this invention, the organic corrosion inhibitor preferably includes one or more of thiourea, benzotriazole and methylbenzotriazole.

[0030] In this invention, the concentration of the organic corrosion inhibitor in the stripping solution is preferably 0.2~1 g / L. As one embodiment, the concentration of the organic corrosion inhibitor in the stripping solution can specifically be 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, or 1 g / L.

[0031] In this invention, the core function of the organic corrosion inhibitor is selective adsorption and protection. The N and S atoms in the inhibitor molecules contain lone pairs of electrons, allowing them to preferentially adsorb onto the active sites of the exposed substrate, forming a dense monomolecular protective film. This effectively blocks contact between the stripping solution and the substrate, significantly increasing the hydrogen evolution overpotential and thus significantly inhibiting the corrosion reaction of the stripping solution on the substrate. However, this protective film has weak or unstable adsorption on zinc and zinc-nickel alloy coatings, so the stripping reaction can still proceed smoothly. This selective inhibition mechanism ensures near-zero damage protection of the substrate while efficiently removing the coating. By controlling the type and concentration of the organic corrosion inhibitor within the aforementioned range, this invention can further reduce or prevent substrate corrosion.

[0032] The stripping solution provided by this invention also includes water.

[0033] In this invention, the water is preferably deionized water. In this invention, the water is used to dissolve other components.

[0034] This invention controls the composition of the stripping solution, utilizing the synergistic effect of organophosphonic acid and fluorides to ensure rapid and thorough removal of pure zinc plating and difficult-to-treat zinc-nickel alloy plating. This solves the problem of the extreme difficulty in stripping zinc-nickel plating. At the same time, the selective adsorption effect of the organic corrosion inhibitor significantly inhibits the over-corrosion of the substrate by the stripping solution. After stripping, the substrate surface is smooth and has high dimensional accuracy, greatly reducing the scrap rate of parts. In addition, the stripping solution is green and environmentally friendly, containing no volatile strong acids, no toxic gases, and no heavy metal oxidants, ensuring a safe production environment and simple wastewater treatment. This invention overcomes the technical defects of existing stripping solutions for zinc and zinc-nickel plating that use hazardous and controlled substances and have unsatisfactory stripping effects.

[0035] In this invention, the method for preparing the stripping solution preferably includes the following steps: (1) Mix some water and organophosphonic acid to obtain an organophosphonic acid solution; (2) Mix some water and fluoride to obtain a fluoride solution; (3) Mix some water and organic corrosion inhibitor to obtain an organic corrosion inhibitor solution; (4) Mix the organophosphonic acid solution obtained in step (1) with the fluoride solution obtained in step (2), then add the organic corrosion inhibitor solution obtained in step (3), and finally add the remaining water to obtain the stripping solution; The steps (1), (2), and (3) are not in any particular order.

[0036] The present invention preferably involves mixing a portion of water with an organophosphonic acid to obtain an organophosphonic acid solution.

[0037] In one implementation, the volume of the water portion is 1 / 3 of the total water volume.

[0038] The present invention does not have any special limitations on the mixing operation of the water and organophosphonic acid; the two can be mixed evenly by means of mixing techniques known to those skilled in the art.

[0039] In this invention, a portion of water and fluoride are mixed to obtain a fluoride solution.

[0040] In one implementation, the volume of the water portion is 1 / 3 of the total water volume.

[0041] The present invention does not have any special limitations on the operation of mixing the water and fluoride; the two can be mixed evenly using mixing techniques well known to those skilled in the art.

[0042] The present invention preferably involves mixing a portion of water with an organic corrosion inhibitor to obtain an organic corrosion inhibitor solution.

[0043] In one implementation, the volume of the water portion is 1 / 4 of the total water volume.

[0044] The present invention does not have any special limitations on the mixing operation of the water and the organic corrosion inhibitor. The two can be mixed evenly by means of mixing techniques known to those skilled in the art.

[0045] After obtaining the organophosphonic acid solution, fluoride solution, and organic corrosion inhibitor solution, the present invention preferably mixes the organophosphonic acid solution and the fluoride solution, then adds the organic corrosion inhibitor solution, and finally adds the remaining water, and matures the mixture to obtain the stripping solution.

[0046] The present invention does not have any special limitations on the operation of mixing the organophosphonic acid solution and the fluoride solution, then adding the organic corrosion inhibitor solution, and finally adding the remaining water. Any technical solution known to those skilled in the art can be used to mix the components evenly.

[0047] In this invention, the curing temperature is preferably 20~30℃; the curing time is preferably 22~25h; and the curing is preferably carried out under static conditions.

[0048] The present invention also provides the application of the stripping solution described above in the removal of zinc and / or zinc-nickel plating.

[0049] In this invention, the preferred application is to immerse a workpiece containing a zinc plating layer and / or a zinc-nickel plating layer in a stripping solution to strip the plating, thereby obtaining a stripped workpiece.

[0050] In this invention, the stripping temperature is preferably 20~60℃. This invention does not have a specific limitation on the stripping time; it can be selected based on the coating thickness.

[0051] When using the stripping solution of the present invention for stripping, the stripping operation is simple and safe, the stripping efficiency is high, and it causes no or only slight corrosion to the substrate.

[0052] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0053] Example 1 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid), fluoride (sodium fluoride), organic corrosion inhibitor (thiourea), and deionized water, wherein the concentration of organophosphonic acid is 0.15 mol / L, the concentration of fluoride is 7.5 g / L, and the concentration of organic corrosion inhibitor is 0.7 g / L. The preparation method of the stripping solution is as follows: (1) Mix 1 / 3 of the total water volume of deionized water with organophosphonic acid and stir until dissolved to obtain an organophosphonic acid solution; (2) Mix 1 / 3 of the total water volume of deionized water with fluoride to obtain a fluoride solution; (3) Mix 1 / 4 of the total water volume of deionized water with the organic corrosion inhibitor to obtain an organic corrosion inhibitor solution; (4) Add fluoride solution to organophosphonic acid solution, then add organic corrosion inhibitor solution, then add the remaining water, and let stand at 25°C for 24 hours to obtain stripping solution.

[0054] Application Example 1 The Q235 steel workpiece with zinc coating was immersed in the stripping solution of Example 1, stripped at 25°C for 50 minutes, washed with deionized water and dried to obtain the stripped workpiece.

[0055] The metallographic structure of the Q235 steel workpiece substrate without the zinc coating in Application Example 1 is shown below. Figure 1 As shown, the X-ray analysis results of the Q235 steel workpiece with a galvanized coating are as follows: Figure 2 As shown.

[0056] The metallographic structure of the workpiece after plating removal in Application Example 1 is shown below. Figure 3 As shown, the X-ray analysis results of the workpiece after plating removal are as follows: Figure 4 As shown.

[0057] from Figures 1-4 As can be seen, before stripping, the thickness of the zinc coating on the surface of the Q235 steel workpiece was 12.3~13.5μm as measured by X-ray coating analyzer. After stripping, the coating thickness was 0~1μm as measured by X-ray coating analyzer, which is basically within the test error range. The zinc coating has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. This proves that the stripping solution in Example 1 has a good stripping effect on the zinc coating on the surface of Q235 steel.

[0058] Comparative Example 1 A stripping solution is composed of the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid), fluoride (sodium fluoride) and deionized water, wherein the concentration of organophosphonic acid is 0.15 mol / L and the concentration of fluoride is 7.5 g / L; The preparation method of the stripping solution is as follows: (1) Mix 1 / 3 of the total water volume of deionized water with organophosphonic acid and stir until dissolved to obtain an organophosphonic acid solution; (2) Mix 1 / 3 of the total water volume of deionized water with fluoride to obtain a fluoride solution; (3) Add fluoride solution to organophosphonic acid solution, then add the remaining water, and let stand at 25°C for 24 hours to obtain stripping solution.

[0059] Comparative Application Example 1 A Q235 steel workpiece with zinc coating (the substrate is the same as in Application Example 1) was immersed in the stripping solution of Comparative Example 1 and stripped at 25°C for 50 minutes. After being washed with deionized water and dried, the workpiece after stripping was obtained.

[0060] Compare the metallographic structure of the workpiece after plating removal in Example 1 as follows: Figure 5 As shown, the X-ray analysis results of the workpiece after plating removal are as follows: Figure 6 As shown.

[0061] from Figures 5-6 As can be seen, before stripping, the thickness of the zinc coating on the surface of the Q235 steel workpiece was 12.5~13.8μm as measured by X-ray coating analyzer. After stripping, the coating thickness was 0~1μm as measured by X-ray coating analyzer, which is basically within the testing error, and the zinc coating has been almost completely removed. However, observation by optical microscope showed that due to the absence of organic corrosion inhibitors in the stripping solution, there were obvious corrosion pits on the surface of the workpiece after stripping, and the substrate showed signs of over-corrosion. Comparing Example 1, Application Example 1, Comparative Example 1 and Comparative Application Example 1, it is demonstrated that the organic corrosion inhibitor thiourea in the stripping solution can significantly inhibit the corrosion reaction of the stripping solution on the substrate through adsorption.

[0062] Example 2 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid and ethylenediaminetetramethylenephosphonic acid), fluoride (ammonium bifluoride), organic corrosion inhibitor (thiourea and benzotriazole), and deionized water, wherein the concentration of organophosphonic acid is 0.2 mol / L (the concentration of hydroxyethylidene diphosphonic acid is 0.1 mol / L, and the concentration of ethylenediaminetetramethylenephosphonic acid is 0.1 mol / L), the concentration of fluoride is 5 g / L, and the concentration of organic corrosion inhibitor is 1 g / L (the concentration of thiourea is 0.2 g / L, and the concentration of benzotriazole is 0.8 g / L). The preparation method of the stripping solution is the same as in Example 1.

[0063] Application Example 2 The 30CrMnSiA high-strength steel workpiece with zinc coating was immersed in the stripping solution of Example 2, stripped at 40°C for 40 minutes, washed with deionized water and dried to obtain the stripped workpiece.

[0064] The metallographic structure of the 30CrMnSiA high-strength steel workpiece matrix without the zinc coating in Application Example 2 is shown below. Figure 7 As shown, the X-ray analysis results of the 30CrMnSiA high-strength steel workpiece with zinc coating are as follows: Figure 8 As shown.

[0065] The metallographic structure of the workpiece after plating removal in Application Example 2 is shown below. Figure 9 As shown, the X-ray analysis results of the workpiece after plating removal are as follows: Figure 10 As shown.

[0066] from Figures 7-10 As can be seen, before stripping, the thickness of the zinc coating on the surface of the 30CrMnSiA high-strength steel workpiece was 15.7~16.8μm as measured by X-ray coating analyzer. After stripping, the coating thickness was 0~1μm as measured by X-ray coating analyzer, which is basically within the test error range. The zinc coating has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. This proves that the stripping solution in Example 2 has a good stripping effect on the zinc coating on the surface of 30CrMnSiA high-strength steel.

[0067] Comparative Example 2 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid and ethylenediaminetetramethylenephosphonic acid), organic corrosion inhibitor (thiourea and benzotriazole), and deionized water, wherein the concentration of organophosphonic acid is 0.2 mol / L (the concentration of hydroxyethylidene diphosphonic acid is 0.1 mol / L, and the concentration of ethylenediaminetetramethylenephosphonic acid is 0.1 mol / L), and the concentration of organic corrosion inhibitor is 1 g / L (the concentration of thiourea is 0.2 g / L, and the concentration of benzotriazole is 0.8 g / L). The preparation method of the stripping solution is as follows: (1) Mix 1 / 3 of the total water volume of deionized water with organophosphonic acid and stir until dissolved to obtain an organophosphonic acid solution; (2) Mix 1 / 4 of the total water volume of deionized water with the organic corrosion inhibitor to obtain an organic corrosion inhibitor solution; (3) Add organic corrosion inhibitor solution to organic phosphonic acid solution, then add the remaining water, and let stand at 25°C for 24 hours to obtain stripping solution.

[0068] Comparative Application Example 2 A 30CrMnSiA high-strength steel workpiece with a zinc coating (the substrate is the same as in Application Example 2) was immersed in the stripping solution of Comparative Example 2.

[0069] Compare the X-ray analysis results of the workpiece in Application Example 2 after stripping at 40°C for 40 minutes as follows: Figure 11 As shown.

[0070] Comparing the metallographic structures of the workpiece in Application Example 2 after stripping at 40°C for 40 minutes and then at 60°C for 40 minutes, the results are as follows: Figure 12 As shown, the X-ray analysis results are as follows: Figure 13 As shown.

[0071] from Figures 11-13 As can be seen, before stripping, the thickness of the zinc coating on the surface of the 30CrMnSiA high-strength steel workpiece was 14.5~15.8μm as measured by an X-ray coating analyzer. When the 30CrMnSiA high-strength steel workpiece with zinc coating was immersed in the stripping solution of Comparative Example 2, after stripping at 40℃ for 40 minutes, the X-ray coating analyzer showed that the coating thickness was still 6~7μm, and the coating was not completely removed. The temperature of the stripping solution was increased to 60℃, and stripping was continued for 40 minutes. After washing with deionized water and drying, the stripped workpiece was obtained. X-ray coating analysis showed that the coating thickness was 0~1μm, which is basically within the testing error range. The zinc coating has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. Comparison with Example 2, Application Example 2, Comparative Example 2, and Comparative Application Example 2 proved that fluoride in the stripping solution can activate the surface and accelerate the initial reaction. When the stripping solution does not contain fluoride, the stripping speed is slow, and it is necessary to increase the stripping temperature and extend the stripping time to achieve a good stripping effect.

[0072] Example 3 A stripping solution comprises the following components: an organophosphonic acid (aminotrimethylenephosphonic acid), a fluoride (potassium fluoride), an organic corrosion inhibitor (benzotriazole and methylbenzotriazole), and deionized water, wherein the concentration of the organophosphonic acid is 0.15 mol / L, the concentration of the fluoride is 7.5 g / L, and the concentration of the organic corrosion inhibitor is 1 g / L (the concentrations of benzotriazole and methylbenzotriazole are 0.5 g / L). The preparation method of the stripping solution is the same as in Example 1.

[0073] Application Example 3 The T2 copper workpiece with zinc plating was immersed in the stripping solution of Example 3, stripped at 60°C for 30 minutes, washed with deionized water and dried to obtain the stripped workpiece.

[0074] Before stripping, the thickness of the zinc plating layer on the surface of the T2 copper workpiece was measured to be 12.5~14.0μm using an X-ray coating analyzer. After stripping, the thickness of the plating layer was measured to be 0~1μm using an X-ray coating analyzer, which is basically within the test error range. The zinc plating layer has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. This proves that the stripping solution in Example 3 has a good stripping effect on the zinc plating layer on the surface of T2 copper.

[0075] Example 4 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid and aminotrimethylene phosphonic acid), fluoride (ammonium bifluoride), organic corrosion inhibitor (benzotriazole), and deionized water, wherein the concentration of organophosphonic acid is 0.3 mol / L (the concentration of hydroxyethylidene diphosphonic acid is 0.15 mol / L, and the concentration of aminotrimethylene phosphonic acid is 0.15 mol / L), the concentration of fluoride is 7.5 g / L, and the concentration of organic corrosion inhibitor is 0.8 g / L; The preparation method of the stripping solution is the same as in Example 1.

[0076] Application Example 4 The Q235 steel workpiece with zinc-nickel alloy plating was immersed in the stripping solution of Example 4, stripped at 60°C for 30 minutes, washed with deionized water and dried to obtain the stripped workpiece.

[0077] The X-ray analysis results of the Q235 steel workpiece with zinc-nickel alloy coating in Application Example 4 are as follows: Figure 14 As shown.

[0078] The metallographic structure of the workpiece after plating removal in Example 4 is shown below. Figure 15 As shown, the X-ray analysis results of the workpiece after plating removal are as follows: Figure 16 As shown.

[0079] from Figures 14-16 As can be seen, before stripping, the thickness of the zinc-nickel alloy layer on the surface of the Q235 steel workpiece was measured to be 10.3~12.7μm by X-ray coating analyzer. After stripping, the coating thickness was measured to be 0~1μm by X-ray coating analyzer, which is basically within the test error. The zinc-nickel alloy layer has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. This proves that the stripping solution in Example 4 has a good stripping effect on the zinc-nickel alloy layer on the surface of Q235 steel.

[0080] Comparative Example 3 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid and aminotrimethylene phosphonic acid), fluoride (ammonium bifluoride) and deionized water, wherein the concentration of organophosphonic acid is 0.3 mol / L (the concentration of hydroxyethylidene diphosphonic acid is 0.15 mol / L, the concentration of aminotrimethylene phosphonic acid is 0.15 mol / L), and the concentration of fluoride is 7.5 g / L; The preparation method of the stripping solution is the same as that of Comparative Example 1.

[0081] Comparative Application Example 3 A Q235 steel workpiece with a zinc-nickel alloy coating (the substrate is the same as in Application Example 4) was immersed in the stripping solution of Comparative Example 3 and stripped at 60°C for 30 minutes. After being washed with deionized water and dried, the stripped workpiece was obtained.

[0082] Compare the metallographic structure of the workpiece after plating removal in Application Example 3 as follows: Figure 17 As shown, the X-ray analysis results of the workpiece after plating removal are as follows: Figure 18 As shown.

[0083] from Figures 17-18 As can be seen, before stripping, the thickness of the zinc-nickel alloy layer on the surface of the Q235 steel workpiece was 11.3~12.5μm as measured by X-ray coating analyzer. After stripping, the coating thickness was 0~1μm as measured by X-ray coating analyzer, which is basically within the testing error range, indicating that the zinc-nickel alloy layer has been almost completely removed. However, observation under an optical microscope revealed obvious corrosion pits on the surface of the workpiece after stripping, indicating over-corrosion of the substrate, due to the absence of organic corrosion inhibitors in the stripping solution. Comparison of Example 4, Application Example 4, Comparative Example 3, and Comparative Application Example 3 demonstrates that the organic corrosion inhibitor benzotriazole in the stripping solution significantly inhibits the corrosion reaction of the stripping solution on the substrate through adsorption.

[0084] Comparative Example 4 A stripping solution comprises the following components: fluoride (ammonium bifluoride), organic corrosion inhibitor (benzotriazole), and deionized water, wherein the concentration of fluoride is 7.5 g / L and the concentration of organic corrosion inhibitor is 0.8 g / L. The preparation method of the stripping solution is as follows: (1) Mix 1 / 3 of the total water volume of deionized water with fluoride to obtain a fluoride solution; (2) Mix 1 / 4 of the total water volume of deionized water with the organic corrosion inhibitor to obtain an organic corrosion inhibitor solution; (3) Add an organic corrosion inhibitor solution to the fluoride solution, then add the remaining water, and let it stand at 25°C for 24 hours to obtain the stripping solution.

[0085] Comparative Application Example 4 A Q235 steel workpiece with a zinc-nickel alloy coating (the substrate is the same as in Application Example 4) was immersed in the stripping solution of Comparative Example 4 and stripped at 60°C for 120 minutes. After being washed with deionized water and dried, the stripped workpiece was obtained.

[0086] Compare the X-ray analysis results of the workpiece after plating removal in Application Example 4 as follows: Figure 19 As shown.

[0087] from Figure 19As can be seen, before stripping, the thickness of the zinc-nickel alloy layer on the surface of the Q235 steel workpiece was 11.5~12.8μm as measured by X-ray coating analyzer. After stripping, the coating thickness was still as high as 9~10μm as measured by X-ray coating analyzer. The diffraction peaks of Zn and Ni were still present and had high intensity. The removal rate of the zinc-nickel coating on the surface was very slow, and it was basically not removed. Comparing Example 4, Application Example 4, Comparative Example 4 and Comparative Application Example 4, it is proved that organophosphonic acid in the stripping solution is the core component of the stripping solution, which can react with zinc (Zn) 2+ ) and nickel (Ni 2+ The ions form a strong complexation reaction, which continuously promotes the coating dissolution reaction. If there is no organophosphonic acid in the stripping solution, the stripping will be very slow or even impossible.

[0088] Example 5 A stripping solution comprises the following components: organophosphonic acid (hydroxyethylidene diphosphonic acid and ethylenediaminetetramethylenephosphonic acid), fluoride (ammonium bifluoride), organic corrosion inhibitor (thiourea and methylbenzotriazole), and deionized water, wherein the concentration of organophosphonic acid is 0.25 mol / L (the concentration of hydroxyethylidene diphosphonic acid is 0.15 mol / L, and the concentration of ethylenediaminetetramethylenephosphonic acid is 0.1 mol / L), the concentration of fluoride is 10 g / L, and the concentration of organic corrosion inhibitor is 1 g / L (the concentration of thiourea is 0.5 g / L, and the concentration of methylbenzotriazole is 0.5 g / L). The preparation method of the stripping solution is the same as in Example 1.

[0089] Application Example 5 The 30CrMnSiA high-strength steel workpiece with zinc-nickel alloy plating was immersed in the stripping solution of Example 5. The workpiece was stripped at 40°C for 30 minutes and then at 60°C for 40 minutes. After being washed with deionized water and dried, the stripped workpiece was obtained.

[0090] Before stripping, the thickness of the zinc-nickel alloy layer on the surface of the 30CrMnSiA high-strength steel workpiece was measured to be 18~20μm using an X-ray coating analyzer. After stripping, the coating thickness was measured to be 0~1μm using an X-ray coating analyzer, which is basically within the testing error range. The zinc-nickel alloy layer has been almost completely removed. Observation under an optical microscope showed that the surface of the workpiece after stripping was smooth, without obvious corrosion pits or residual corrosion products, and the substrate had not experienced any corrosion. This proves that the stripping solution in Example 5 has a good stripping effect on the zinc-nickel alloy layer on the surface of the 30CrMnSiA high-strength steel.

[0091] In summary, the stripping solution provided by this invention has a good stripping effect and will not cause over-corrosion to the substrate, while also being green and environmentally friendly.

[0092] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A stripping solution comprising the following components: organophosphonic acid, fluoride, organic corrosion inhibitor and water.

2. The stripping solution according to claim 1, characterized in that, The organophosphonic acid includes one or more of hydroxyethylidene diphosphonic acid, aminotrimethylenephosphonic acid, and ethylenediaminetetramethylenephosphonic acid.

3. The stripping solution according to claim 1 or 2, characterized in that, The concentration of organophosphonic acid in the stripping solution is 0.1~0.4 mol / L.

4. The stripping solution according to claim 1, characterized in that, The fluoride includes one or more of sodium fluoride, potassium fluoride, and ammonium bifluoride.

5. The stripping solution according to claim 1 or 4, characterized in that, The concentration of fluoride in the stripping solution is 2.5~10 g / L.

6. The stripping solution according to claim 1, characterized in that, The organic corrosion inhibitor includes one or more of thiourea, benzotriazole, and methylbenzotriazole.

7. The stripping solution according to claim 1 or 6, characterized in that, The concentration of the organic corrosion inhibitor in the stripping solution is 0.2~1g / L.

8. The use of the stripping solution according to any one of claims 1 to 7 in the removal of zinc and / or zinc-nickel plating.

9. The application according to claim 8, characterized in that, The workpiece containing zinc plating and / or zinc-nickel plating is immersed in a stripping solution to remove the plating, resulting in a stripped workpiece.

10. The application according to claim 9, characterized in that, The temperature for stripping is 20~60℃.

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