Stainless steel electrochemical polishing solution as well as preparation method and application thereof

Abstract

The invention discloses a stainless steel electrochemical polishing solution and a preparation method and application thereof, and belongs to the technical field of electrolytic polishing. The invention provides a stainless steel electrochemical polishing solution which is composed of phosphoric acid, concentrated sulfuric acid, polyacrylamide, organic acid, a nonionic surfactant, a brightener, a corrosion inhibitor and deionized water according to a specific proportion, the leveling property and filling property of the electrochemical polishing solution are controlled by adding the polyacrylamide, so that the electrochemical polishing solution can better cover the surface of a workpiece, and the corrosion resistance of the workpiece is improved. Dirt, scratches and flaws on the surface are more effectively removed, and then the smoothness of the surface of the workpiece is improved. Meanwhile, the stainless steel polishing solution also has the characteristics of reducing the surface roughness of the stainless steel, improving the smoothness, the smoothness and the corrosion resistance, being environment-friendly and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolytic polishing, and in particular relates to a stainless steel electrochemical polishing liquid and a preparation method and application thereof. Background Art

[0002] Electrochemical polishing is an important electrochemical surface treatment technology developed abroad in the 1980s. With the workpiece being polished serving as the anode and an insoluble metal (or inert conductor) serving as the cathode, both electrodes are immersed in a specific electrolyte and a direct current is passed through them, causing selective anodic dissolution, thereby flattening the metal surface and imparting a metallic sheen. Compared to other surface treatment methods (such as mechanical polishing and chemical polishing), electrochemical polishing offers the following significant advantages: higher polishing quality; no mechanical damage; uniform polishing of complex shapes, internal holes, deep grooves, and fine structures that are difficult to reach with traditional tools; and the formation of a dense oxide film during the polishing process, which significantly enhances corrosion resistance.

[0003] Electrochemical polishing of stainless steel is widely used in fields such as biomedicine, medical devices, fine chemicals, and polymerization engineering. Many conventional electrochemical polishing fluids contain chromic anhydride, which produces hexavalent chromium during use. This is seriously harmful to the environment and human health, can be carcinogenic, and is difficult to handle. Current polishing fluids lose their effectiveness after a period of use, producing wastewater with complex composition. Furthermore, they present issues such as unstable polishing results, poor polishing quality, complex process parameter control, and environmental and safety concerns. Therefore, there is an urgent need to develop an electrochemical polishing fluid suitable for fine stainless steel machining that is both energy-efficient and environmentally friendly. Summary of the Invention

[0004] The present invention provides a stainless steel electrochemical polishing liquid, its preparation method, and its application. By adding polyacrylamide to the electrochemical polishing liquid, the liquid's leveling and filling properties are controlled, allowing it to better cover the workpiece surface, more effectively removing surface dirt, scratches, and blemishes, thereby improving the workpiece's surface finish. Furthermore, the present invention reduces stainless steel surface roughness, improves surface finish, flatness, and corrosion resistance, and is environmentally friendly.

[0005] To achieve the above object, the technical solution of the present invention is:

[0006] A stainless steel electrochemical polishing liquid, comprising phosphoric acid, concentrated sulfuric acid, polyacrylamide, organic acid, nonionic surfactant, brightener, corrosion inhibitor and deionized water;

[0007] The volume ratio of the phosphoric acid, concentrated sulfuric acid, corrosion inhibitor and deionized water is: phosphoric acid: concentrated sulfuric acid: corrosion inhibitor: deionized water = (5-6): (2-3): (0.3-0.5): (1-2);

[0008] The mass ratio of the polyacrylamide, organic acid, nonionic surfactant, brightener and deionized water is: polyacrylamide: organic acid: nonionic surfactant: brightener: deionized water = (0.1-0.2): (1-3): (0.5-1): (1-2): (100-200);

[0009] The mass fraction of the phosphoric acid is 70% to 85%, and the mass fraction of the concentrated sulfuric acid is 92% to 98%.

[0010] The organic acid is selected from at least one of malic acid, citric acid, and succinic acid;

[0011] The nonionic surfactant is selected from at least one of lauryl alcohol polyoxyethylene ether, Span 20, Span 40, Tween 80, and lauroyl diethanolamide.

[0012] The brightening agent is selected from at least one of saccharin, sulfosalicylic acid and benzotriazole.

[0013] The corrosion inhibitor is selected from at least one of ethanol, ethylene glycol and glycerol.

[0014] The preparation of the stainless steel electrochemical polishing liquid comprises the following steps:

[0015] Adding polyacrylamide, organic acid, nonionic surfactant, brightener, corrosion inhibitor, phosphoric acid, and concentrated sulfuric acid to deionized water in sequence; wherein, each reagent is added in sequence, stirred evenly before adding the next one, and after all reagents are added and stirred evenly, the stainless steel electrochemical polishing solution is obtained;

[0016] The application of the stainless steel electrochemical polishing liquid comprises the following steps:

[0017] Pretreatment: grinding and cleaning of stainless steel;

[0018] Polishing treatment: The pre-treated stainless steel is connected to the positive electrode of the power supply and immersed in the stainless steel electrochemical polishing liquid for electrochemical polishing.

[0019] Preferably, at least one of (1) to (4) is satisfied:

[0020] (1) The current density of electrochemical polishing is: 10A / dm 2 ~25A / dm 2 , the temperature of the electrochemical polishing solution is 50℃~70℃, and the polishing time is 1min~5min;

[0021] (2) The area ratio of cathode to anode is (2-1):1;

[0022] (3) Stirring the electrochemical polishing solution during the polishing process to promote uniform distribution of the solution;

[0023] (4) A cleaning step is also included after the electrochemical polishing treatment.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The stainless steel electrochemical polishing liquid provided by the present invention controls the leveling and filling properties of the electrochemical polishing liquid by adding polyacrylamide, so that the electrochemical polishing liquid can better cover the surface of the workpiece, more effectively remove dirt, scratches and blemishes on the surface, and thus improve the surface finish of the workpiece. The present invention is not only suitable for the precision polishing of stainless steel, reducing surface roughness, and improving the cleanliness and brightness of the stainless steel surface, but also can form a corrosion-resistant oxide film on the surface of the stainless steel, thereby improving the corrosion resistance of the stainless steel. Since the components of the stainless steel electrochemical polishing liquid of the present invention are not easy to volatilize, atmospheric pollution is effectively reduced, and it does not contain chromium elements and is environmentally friendly. In addition, the stainless steel electrochemical polishing liquid of the present invention can be used multiple times after supplementing a certain amount of phosphoric acid and sulfuric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Surface metallographic images of samples obtained from different embodiments and comparative examples of the present invention; wherein (a) is the comparative example, (b) is Example 1, (c) is Example 2, and (d) is Example 3;

[0027] Figure 2 Surface roughness test results of samples obtained from different embodiments and comparative examples of the present invention are shown in FIG.

[0028] Figure 3 The potentiodynamic polarization curves of the samples obtained in different embodiments and comparative examples of the present invention are shown;

[0029] Figure 4 The electrochemical impedance spectra of samples obtained from different embodiments and comparative examples of the present invention are shown. DETAILED DESCRIPTION

[0030] The present invention provides a stainless steel electrochemical polishing solution, which is composed of phosphoric acid, concentrated sulfuric acid, polyacrylamide, organic acid, nonionic surfactant, brightener, corrosion inhibitor, and deionized water. The volume ratio of phosphoric acid, concentrated sulfuric acid, corrosion inhibitor, and deionized water is: phosphoric acid: concentrated sulfuric acid: corrosion inhibitor: deionized water = (5-6): (2-3): (0.3-0.5): (1-2). The mass ratio of polyacrylamide, organic acid, nonionic surfactant, brightener, and deionized water is: polyacrylamide: organic acid: nonionic surfactant: brightener: deionized water = (0.1-0.2): (1-3): (0.5-1): (1-2): (100-200).

[0031] The mass fraction of phosphoric acid in the present invention is 70% to 85%, and the mass fraction of concentrated sulfuric acid is 92% to 98%.

[0032] In the present invention, the organic acid is selected from at least one of malic acid, citric acid, and succinic acid; the nonionic surfactant is selected from at least one of lauryl alcohol polyoxyethylene ether, Span 20, Span 40, Tween 80, and lauroyl diethanolamine; the brightener is selected from at least one of saccharin, sulfosalicylic acid, and benzotriazole; and the corrosion inhibitor is selected from at least one of ethanol, ethylene glycol, and glycerol.

[0033] The present invention also provides a method for preparing the stainless steel electrochemical polishing liquid, comprising the following steps: adding polyacrylamide, an organic acid, a nonionic surfactant, a brightener, a corrosion inhibitor, phosphoric acid, and concentrated sulfuric acid to deionized water in sequence; wherein, each reagent is added in sequence, stirred evenly, and then the next one is added. After all reagents are added and stirred evenly, the stainless steel electrochemical polishing liquid is obtained.

[0034] The application of the stainless steel electrochemical polishing liquid provided by the present invention comprises the following steps:

[0035] Pretreatment: grinding and cleaning of stainless steel;

[0036] Polishing treatment: The pre-treated stainless steel is connected to the positive electrode of the power supply and immersed in the stainless steel electrochemical polishing liquid for electrochemical polishing.

[0037] The present invention provides an application of a stainless steel electrochemical polishing liquid, which further satisfies at least one of (1) to (4):

[0038] (1) The current density of electrochemical polishing is: 10A / dm 2 ~25A / dm 2 , the temperature of the electrochemical polishing solution is 50℃~70℃, and the polishing time is 1min~5min;

[0039] (2) The area ratio of cathode to anode is (2-1):1;

[0040] (3) Stirring the electrochemical polishing solution during the polishing process to promote uniform distribution of the solution;

[0041] (4) A cleaning step is also included after the electrochemical polishing treatment.

[0042] The present invention will now be described in further detail. The embodiments described below are exemplary and are intended to describe the present invention in more detail and specific manner, but should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work shall fall within the scope of protection of the present invention.

[0043] Example 1:

[0044] The stainless steel electrochemical polishing liquid provided in this embodiment is prepared from the following raw materials: 550 mL of 85 wt % phosphoric acid, 220 mL of 98 wt % concentrated sulfuric acid, 0.1 g of polyacrylamide, 2 g of malic acid, 0.7 g of lauryl alcohol polyoxyethylene ether, 1.5 g of saccharin, 40 mL of glycerol, and 150 mL of deionized water, and prepared according to the following steps:

[0045] According to the above proportions, polyacrylamide, malic acid, lauryl polyoxyethylene ether, saccharin, glycerol, phosphoric acid, and concentrated sulfuric acid are added to deionized water in sequence. Each reagent is added in sequence, stirred evenly, and then the next one is added. After all reagents are added and stirred evenly, a stainless steel electrochemical polishing liquid is obtained.

[0046] Polishing stainless steel using the above-mentioned stainless steel electrochemical polishing liquid includes the following steps:

[0047] Pretreatment: Wire-cut machining was used to the specified dimensions. The specimens were then mechanically polished using 400#, 1000#, and 2000# sandpaper in ascending grits. The specimens were then ultrasonically cleaned in acetone for 20 minutes and then placed in an air drying oven to remove any residual acetone.

[0048] Polishing treatment: connect the stainless steel sample to the positive electrode of the power supply, use the lead plate as the cathode material, the anode and cathode area ratio is 2:1, and the current density is 10A / dm 2 The electrochemical polishing liquid temperature was 60°C, the polishing time was 5 minutes, and the electrochemical polishing liquid was stirred during the polishing process. After polishing, the surface was rinsed under running deionized water for 2 minutes and dried with cold air.

[0049] Example 2:

[0050] The stainless steel electrochemical polishing liquid provided in this embodiment is prepared using the following raw materials: 580 mL of 80 wt % phosphoric acid, 240 mL of 95 wt % concentrated sulfuric acid, 0.1 g of polyacrylamide, 1.7 g of succinic acid, 0.7 g of Span 20, 2 g of saccharin, 40 mL of ethanol, and 200 mL of deionized water, prepared according to the steps of Example 1.

[0051] Polishing stainless steel using the above-mentioned stainless steel electrochemical polishing liquid includes the following steps:

[0052] Pretreatment: Wire-cut machining was used to the specified dimensions. The specimens were then mechanically polished using 400#, 1000#, and 2000# sandpaper in ascending grits. The specimens were then ultrasonically cleaned in acetone for 20 minutes and then placed in an air drying oven to remove any residual acetone.

[0053] Electrochemical polishing: connect the stainless steel sample to the positive electrode of the power supply, use stainless steel as the cathode material, the anode and cathode area ratio is 1:1, and the current density is 20A / dm 2 The electrochemical polishing liquid temperature was 50°C, the polishing time was 2 minutes, and the electrochemical polishing liquid was stirred during the polishing process. After polishing, the surface was rinsed under running deionized water for 2 minutes and dried with cold air.

[0054] Example 3:

[0055] The stainless steel electrochemical polishing liquid provided in this embodiment is prepared using the following raw materials: 500 mL of 80 wt % phosphoric acid, 200 mL of 92 wt % concentrated sulfuric acid, 0.2 g of polyacrylamide, 0.5 g of malic acid, 1 g of citric acid, 0.5 g of lauryl alcohol polyoxyethylene ether, 1.5 g of sulfosalicylic acid, 50 mL of glycerol, and 180 mL of deionized water, and is prepared according to the steps of Example 1.

[0056] Polishing stainless steel using the above-mentioned stainless steel electrochemical polishing liquid includes the following steps:

[0057] Pretreatment: Wire-cut machining was used to the specified dimensions. The specimens were then mechanically polished using 400#, 1000#, and 2000# sandpaper in ascending grits. The specimens were then ultrasonically cleaned in acetone for 20 minutes and then placed in an air drying oven to remove any residual acetone.

[0058] Electrochemical polishing: connect the stainless steel sample to the positive electrode of the power supply, use stainless steel as the cathode material, the anode and cathode area ratio is 1:1, and the current density is 25A / dm 2 The electrochemical polishing liquid temperature was 60°C, the polishing time was 3 minutes, and the electrochemical polishing liquid was stirred during the polishing process. After polishing, the surface was rinsed under running deionized water for 2 minutes and dried with cold air.

[0059] Comparative Example:

[0060] The specimens were machined to the specified dimensions using wire cutting and mechanically polished using 400#, 1000#, and 2000# sandpaper in ascending grits. The specimens were then ultrasonically cleaned in acetone for 20 minutes and then placed in an air drying oven to remove any residual acetone.

[0061] In order to verify the performance of the stainless steel electrochemical polishing solutions of Examples 1 to 3 of the present invention, the stainless steel samples after electrochemical polishing in the comparative example and Examples 1 to 3 of the present invention were subjected to metallographic microscope observation, surface roughness measurement, potentiodynamic polarization curve analysis, and electrochemical impedance spectroscopy analysis.

[0062] Depend on Figure 1 It can be seen that compared with the comparative example, the surface scratches of the stainless steel samples in Examples 1 to 3 are significantly reduced, and the smoothness and flatness are significantly improved; Figure 2 It can be seen that the surface roughness of the stainless steel sample in the comparative example is 0.150 μm, and the surface roughness of the stainless steel samples in Examples 1 to 3 are similar, and are significantly lower than that in the comparative example, which are 0.052 μm, 0.062 μm, and 0.058 μm respectively. Figure 3 It can be seen that the corrosion potential of the stainless steel samples in Examples 1 to 3 is significantly higher than that in the comparative example, and the fitting results of the potentiodynamic polarization curves are shown in Table 1. Figure 4 It can be seen that the curvature of the impedance radius of the samples of Examples 1 to 3 increases significantly after electrochemical polishing.

[0063] The above performance tests show that the stainless steel electrochemical polishing solution provided by the present invention can significantly reduce the surface roughness of stainless steel, improve the smoothness, flatness and corrosion resistance. At the same time, the present invention does not contain Cr and is environmentally friendly.

[0064] Table 1. Potentiodynamic polarization curve fitting results

[0065]

[0066] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention. Those skilled in the art may devise numerous modifications, variations, and alternatives without departing from the spirit and scope of the present invention. It should be understood that various alternatives to the embodiments of the present invention described herein may be employed in the practice of the present invention.

Claims

1. A stainless steel electrochemical polishing liquid, characterized in that: The invention is composed of phosphoric acid, concentrated sulfuric acid, polyacrylamide, organic acid, non-ionic surfactant, brightener, corrosion inhibitor and deionized water.

2. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The volume ratio of the phosphoric acid, concentrated sulfuric acid, corrosion inhibitor and deionized water is: phosphoric acid: concentrated sulfuric acid: corrosion inhibitor: deionized water = (5-6): (2-3): (0.3-0.5): (1-2); The mass fraction of the phosphoric acid is 70% to 85%, and the mass fraction of the concentrated sulfuric acid is 92% to 98%.

3. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The mass ratio of the polyacrylamide, organic acid, nonionic surfactant, brightener and deionized water is polyacrylamide: organic acid: nonionic surfactant: brightener: deionized water = (0.1-0.2): (1-3): (0.5-1): (1-2): (100-200).

4. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The organic acid is selected from at least one of malic acid, citric acid and succinic acid.

5. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The brightening agent is selected from at least one of saccharin, sulfosalicylic acid and benzotriazole.

6. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The corrosion inhibitor is selected from at least one of ethanol, ethylene glycol and glycerol.

7. The electrochemical polishing liquid for stainless steel according to claim 1, characterized in that: The nonionic surfactant is selected from at least one of lauryl alcohol polyoxyethylene ether, Span 20, Span 40, Tween 80, and lauroyl diethanolamide.

8. The method for preparing a stainless steel electrochemical polishing liquid according to any one of claims 1 to 7, characterized in that: Polyacrylamide, organic acid, nonionic surfactant, brightener, corrosion inhibitor, phosphoric acid and concentrated sulfuric acid are added to deionized water in sequence; wherein, each reagent is added in sequence, stirred evenly and then the next one is added, and after all reagents are added and stirred evenly, the stainless steel electrochemical polishing liquid is obtained.

9. Use of a stainless steel electrochemical polishing liquid according to any one of claims 1 to 7, characterized in that: The following steps are involved: Pretreatment: grinding and cleaning of stainless steel; Polishing treatment: The pre-treated stainless steel is connected to the positive electrode of the power supply and immersed in the stainless steel electrochemical polishing liquid for electrochemical polishing.

10. The use of a stainless steel electrochemical polishing liquid according to claim 9, characterized in that: Satisfy at least one of (1)-(4): (1) The current density of electrochemical polishing is: 10A / dm 2 ~25A / dm 2 , the temperature of the electrochemical polishing solution is 50℃~70℃, and the polishing time is 1min~5min; (2) The area ratio of cathode to anode is (2-1):1; (3) stirring the electrochemical polishing solution during the polishing process; (4) A cleaning step is also included after the electrochemical polishing treatment.

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